Getting Horses Fit: A Guide to Improving Performance

cover title author publisher isbn10 | asin print isbn13 ebook isbn13 language subject publication date lcc ddc subject ...

Author: Sarah Pilliner | Zoe Davies

64 downloads 2080 Views 2MB Size Report

This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!

Report copyright / DMCA form

DOWNLOAD PDF

cover

title author publisher isbn10 | asin print isbn13 ebook isbn13 language subject publication date lcc ddc subject

: : : : : : : : : : :

next page >

Getting Horses Fit : A Guide to Improving Performance Pilliner, Sarah.; Davies, Zoe. Blackwell Publishing Ltd. 9780632048113 9780632060177 English Show horses, Show horses--Training, Show horses--Diseases. 2000 SF295.185.P54 2000eb 636.1/0888 Show horses, Show horses--Training, Show horses--Diseases.

cover

next page >

< previous page

page_i

next page > Page i

Getting Horses Fit A Guide to Improving Performance Third Edition Sarah Pilliner MSc, BHSI (SM) Zoe Davies MSc

< previous page

page_i

next page >

< previous page

page_ii

next page > Page ii

© Sarah Pilliner 1986, 1993 © Third Edition Sarah Pilliner & Zoe Davies 2000 Blackwell Science Ltd Editorial Offices: Osney Mead, Oxford OX2 0EL 25 John Street, London WC1N 2BL 23 Ainslie Place, Edinburgh EH3 6AJ 350 Main Street, Malden MA 02148 5018, USA 54 University Street, Carlton Victoria 3053, Australia 10, rue Casimir Delavigne 75006 Paris, France Other Editorial Offices: Blackwell Wissenschafts-Verlag GmbH Kurfürstendamm 57 10707 Berlin, Germany Blackwell Science KK MG Kodenmacho Building 710 Kodenmacho Nihombashi Chuo-ku, Tokyo 104, Japan The right of the Author to be identified as the Author of this Work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. First published in Great Britain by Collins Professional Books 1986 Reprinted 1987 Reprinted by BSP Professional Books 1988, 1989, 1990, 1991 Second Edition published by Blackwell Science 1994 Reprinted 1994, 1996 (twice) Third Edition 2000 Set in 11/13pt Times by DP Photosetting, Aylesbury, Bucks Printed and bound in Great Britain by The Alden Group, Oxford The Blackwell Science logo is a trade mark of Blackwell Science Ltd, registered at the United Kingdom Trade Marks Registry DISTRIBUTORS Marston Book Services Ltd PO Box 269 Abingdon Oxon OX14 4YN (Orders: Tel: 01235 465500 Fax: 01235 465555)

USA Blackwell Science, Inc. Commerce Place 350 Main Street Malden, MA 02148 5018 (Orders: Tel: 800 759 6102 781 388 8250 Fax: 781 388 8255) Canada Login Brothers Book Company 324 Saulteaux Crescent Winnipeg, Manitoba R3J 3T2 (Orders: Tel: 204 837-2987 Fax: 204 837-3116) Australia Blackwell Science Pty Ltd 54 University Street Carlton, Victoria 3053 (Orders: Tel: 03 9347 0300 Fax: 03 9347 5001) A catalogue record for this title is available from the British Library ISBN 0-632-04811-5 Library of Congress Cataloging-in-Publication Data Pilliner, Sarah. Getting horses fit : improve your horse's performance / Sarah Pilliner Zoe Davies. 3rd ed. p. cm ISBN 0-632-04811-5 1. Show horses. 2. Show horses Training. 3. Show horsesDiseases. I. Davies, Zoe. II. Title. SF295.185.P54 2000 636.1'0888dc21 00-029789 For further information on Blackwell Science, visit our website: www.blackwell-science.com

< previous page

page_ii

next page >

< previous page

page_iii

next page > Page iii

CONTENTS

Preface

iv

Part I: Achieving Fitness

1

1 The Aim of Training

3

2 Traditional Training Methods

8

Part II: How the Horse Works

19

Introduction

19

3 The Respiratory System

21

4 The Muscle System

31

5 The Circulatory System

42

6 Bone and Hoof Structure

64

7 The Dental System

79

Summary of Part II

82

Part III: The Performance Horse Health Problems

85

8 Lameness

87

9 Metabolic Disorders

102

10 Respiratory Problems

109

11 Heatstroke and Dehydration

118

12 Internal parasites

129

Part IV: The High-Performance Horse Management and Training

135

13 Nutrition of the Performance Horse

137

14 The Utilisation of Nutrients During Exercise

181

15 Care of the Performance Horse

192

16 Interval Training and Getting the Event Horse Fit

199

17 Fitness for Other Disciplines

220

18 The Speedtest and Fartlek System

247

19 Monitoring Fitness

251

20 Equine Sports Physiology

255

Conclusion

269

Appendix: A Guide to Speeds and Paces

270

Glossary

271

Index

282

< previous page

page_iii

next page >

< previous page

page_iv

next page > Page iv

PREFACE Sarah Pilliner has combined her knowledge and expertise with that of Zoe Davies to update this 2000 edition of Getting Horses Fit. Fittening competition horses to perform at their best, over a period of time requires both understanding and practical ability. The aim of this book is to explain in simple terms, the art and science of the training process and the problems and difficulties which often arise. The changes that take place in the horse's body during exercise and training are described. This knowledge can then be used to devise suitable training programmes for disciplines as diverse as long-distance riding and three-day eventing. Since the first edition of this book was published, equine exercise physiology has become an established science and, together with new research into veterinary care and nutrition, the science of training horses has seen major advances. These scientific ideas may then be combined with the 'art' of managing horses to ensure their health and fitness over a long period of time. The importance of nutrition in the management of competition horses cannot be overstated and this book explains the fate of nutrients and how they are used to give the horse energy for work. Getting Horses Fit provides a clear and concise guide to fittening the horse, including stable management and a fittening regime, enabling horseowners to devise their own successful training programme. Practical aspects covering management of horses, pre- and post-competition, including new information on cooling horses down are discussed. There has been an explosion of interest and activity in equine sports therapy and the role of the equine therapist as part of the team is now an essential one. This book examines the sports therapist's role and the practical implications. Finally, this third edition aims to provide horse owners and trainers with an understandable guide to the fittening process, encompassing new scientific ideas which can then be used in practice. These ideas and principles help to achieve a high level of fitness and maintain the horse's health during its competitive life. All photographs are by Alison Francis unless otherwise stated. SARAH PILLINER ZOE DAVIES

< previous page

page_iv

next page >

< previous page

page_1

next page > Page 1

PART I ACHIEVING FITNESS

< previous page

page_1

next page >

< previous page

page_3

next page > Page 3

1 The Aim of Training What Is Fitness? Fitness can be defined as being in a state suitable for an effort or act, and the level of fitness will be determined by the type of effort or act that is to be performed. In other words, each equestrian sport will demand a specific level and type of fitness from the horse, and a horse fit for one sport may not be fit for another. A showjumper fit enough to jump Grade A courses would not be fit enough to complete a three-day event without being distressed. How Is Fitness Achieved? To obtain fitness, to get a horse fit or to condition it, a combination of correct work and feeding is necessary. Together, work and feeding are known as 'training'. It is important at this stage to establish what is meant by work: a physics textbook will tell you that work is 'the effort made when a load is moved over a set distance'. This is easily understood in terms of a horse carrying a rider or pulling a load over a set course. The aim of getting a horse fit, or 'conditioning' a horse, is to enable the horse to undergo a set amount of work with minimum fatigue. Obviously, the degree of fitness necessary will depend on the severity of the work. The basis of any method of conditioning is to increase the horse's ability to tolerate work by giving it gradually increasing amounts of work to do during its training programme. This slow, steady progression of exercise levels is fundamental for both the physical and mental well-being of the horse, building confidence and security as a result of individual attention. The Importance of Health 'Winning condition' is built and maintained on a foundation of good health. Athletic performance makes great demands on the horse's

< previous page

page_3

next page >

< previous page

page_4

next page > Page 4

body; a healthy body is better able to withstand the stress of physical activity. The trainer and rider must aware of the signs of good health and be able to respond to the most subtle indications of ill health. The three most easily monitored signs of health are temperature, pulse and respiration. The values of these vital signs should fall within a 'normal' range. However, each horse will vary slightly and the trainer should know the values for each individual horse. Unless the horse's normal temperature, pulse and respiration (TPR) are known, any deviation from normal, indicating stress, will not be easy to evaluate. The TPR should be measured when the horse is calm and at rest (the method is described in detail in Chapter 16.) The horse's normal temperature range is about 38°C (100101°F). This value will rise after exertion and if the horse is fevered. A fall in temperature may indicate shock. The resting pulse rate normally lies between 36 and 42 beats per minute. This value will rise with exertion, fear, excitement and fever. The resting respiration rate is usually about 8 to 16 breaths per minute. As before, this value will rise with exercise, excitement, etc. Respiratory disease may also cause the horse to have an abnormally high breathing rate. If the trainer has any doubt about a horse's health, the veterinary surgeon can be asked to take blood tests. The results of a blood test, while not infallible, can be useful in helping the vet to diagnose illness and assess the horse's fitness. The meaning of the test results are discussed later. Exercise and Fitness. Assuming that the horse is healthy, fitness is obtained by giving it exercise. This exercise can be either general or specific. Walking and trotting are excellent general conditioning exercises, and the horse should be walked before and after work as this starts the warm-up process and increases the circulation of blood throughout the body. The hoof is a specialised structure designed to pump blood by the pressure of the horse's weight on the foot; thus preexercise walking improves the blood circulation in the legs and prepares them for the stress of faster work. After exercise, walking helps to decrease the blood circulation slowly so that the horse is able to recover from the stress of exercise more efficiently. Horses intended for specific performance will need special exercises to develop the muscles and associated structures used most strenuously; for example, the showjumper needs a strong back and hind-

< previous page

page_4

next page >

< previous page

page_5

next page > Page 5

quarters, and the racehorse needs special attention to the legs. Also, specific exercises must be used to develop weak areas which may be due to injuries or conformational defects. Each Horse Is an Individual When exercise is combined with the correct feeding of a balanced diet, the horse will gradually become more and more fit, until it is capable of dealing with the task demanded of it. However, training is not that simple as each horse is an individual and that individual is constantly changing both physically and mentally. The appearance and temperament of a horse will be influenced by day-to-day variations in its environment. Every day is different and presents a different challenge. The horse is not a machine and cannot be expected to behave like one. This means that in order to obtain full realisation of a horse's potential the trainer must be able to understand and appreciate the limitations and capabilities of that horse in the various situations with which they confront it. The unique characteristics of a horse can influence how it reacts to and accepts a training programme, and these characteristics must be considered when formulating and carrying out such a programme. The Training Programme Some of the factors that will influence a programme include: Age. Younger horses, particularly those that have not yet reached maturity, are in many cases not physically able to withstand the stress of rigorous training, yet younger horses require more daily exercise than older horses to stay fit. Previous training. Once a horse has been brought to peak fitness it is much easier to get it fit again. Length of rest. The shorter a break the horse has had, the easier it will be to get fit. Temperament. Some horses are lazy while others are keen. The keen horse may be easy to get fit and difficult to keep calm; the lazy horse may need more work to get fit but keep its condition and be more placid. Soundness. If a horse has a history of unsoundness for example, tendon problems the training programme may have to take longer and avoid too much fast work. Conformational weaknesses must also be taken into consideration because these may predispose the horse to unsoundness.

< previous page

page_5

next page >

< previous page

page_6

next page > Page 6

Type, including weight, size and height of horse, must also be taken into consideration. The competitive goal or goals will also have a great influence on the type and length of training programme chosen. Horses should not be got overfit and so become difficult to manage for the young or inexperienced rider. Learning Learning is an important part of training, particularly when training the young horse. The horse is a herd animal, and as one of the herd it is accustomed to being guided by the behaviour of the herd leader. The average horse does not have much individual initiative compared to many other animals and, because of this, is often uncertain how to behave when it is alone. The rider or trainer exploits this characteristic by dominating the horse, and must be confident, consistent and quietly forceful, thus putting the horse at ease. The horse is most at ease when it knows what behaviour is expected of it. If the rider or trainer loses confidence, this is immediately communicated to the horse and it, too, becomes uncertain. Reducing Stress To obtain the best performance from the horse demands optimum conditioning of all the body systems involved during the specific work the horse is asked to perform. A fit horse is less likely to be completely fatigued at the end of its workout for example, a race. This is important, because fatigue contributes to breakdown. Both the intensity and the duration of the training programme will affect the degree of fitness obtained. However, it must always be remembered that there are limits beyond which different systems cannot be pushed without risking damage. For example, there is no point in developing muscle to the point where the horse starts to develop bone and joint problems. In simple terms, both trainer and rider have to have an indefinable quality known as 'feel': knowing horses and anticipating their reactions. Feel is largely acquired by years of experience, aided by an innate sensitivity for which there is no substitute. The object of the following chapters is to help trainers and riders attain a better knowledge of how their horse's body works and how it adapts to training. This knowledge can then be used to design training programmes that do not overstress the horse and thus have better long-term results.

< previous page

page_6

next page >

< previous page

page_7

next page > Page 7

Stable Management Today's trainers and riders must not be blinded by science and technology, but should benefit from a mixture of horsesense from the past and modern knowledge. Commonsense must not be lost sight of. The basic principles of horse and stable management are very important and can be summarised as follows: An airy, safe loose box with no draughts. Well-fenced, clean grazing. Fresh, clean forage with a high nutrient content. A constant supply of clean water. Thorough grooming. Shoeing. Exercise programme encompassing all stages of training. Nutrition programme encompassing all stages of training. These must all be incorporated into a daily routine to get the best from the horse. The significance of each of these factors is explained later, but each is of vital importance to an optimum training regime.

< previous page

page_7

next page >

< previous page

page_8

next page > Page 8

2 Traditional Training Methods The horse has been domesticated for thousands of years. It is probable that our ancestors initially herded horses as meat animals but then realised that here was an animal that could not only cover great distances but was also capable of high speed. The horse became indispensable as a working animal and very stringent demands were made upon it in terms of speed and endurance; consequently, a high degree of fitness was needed. Getting the Hunter Fit Foxhunting developed in the eighteenth and nineteenth centuries to become a premier equestrian sport, and from the training of horses used for foxhunting developed the traditional methods of getting horses fit from grass which are outlined below. These are tried and trusted methods used by generations of grooms to get horses fit for the November Opening Meet, with October cubhunting supplying some of the fast work needed for true fitness. When getting horses which are not going to hunt fit, the fast work must be included in the training programme itself, and this, too, will be outlined. Traditionally, hunters are brought up from grass on 1 August, allowing 3 months to get them fit enough for a hard day's hunting the equivalent of which would be a one-day event or a 32 km (20 mile) distance ride. This 3-month period can be split into three 4-week periods: preliminary work, development work, and fast work. It is important that adequate time is spent on each of these periods, so that a depth of fitness is gradually built up. Modern competition horses are rarely given such long rest periods at grass as is traditional for hunters and therefore may be fittened in less time. Getting a Horse up from Grass Getting a horse fit involves exercise, feeding and overall stable management. Before embarking on an exercise programme, some routine

< previous page

page_8

next page >

< previous page

page_9

next page > Page 9

procedures should be carried out which are essential to the health and well-being of the animal. Management Routines. Shoeing. The farrier should be called to check the horse's feet and fit a new set of shoes. Stud holes will probably not be necessary at this stage. New shoes should be fitted every 4 to 6 weeks while the horse is in work. Teeth. The teeth should be checked for sharpness and unevenness. Any sharp edges will need rasping by the vet or horse dentist so that the horse does not experience discomfort when eating or when the bit is in its mouth. Young horses (up to 5 years old) should also be checked for the loss of milk teeth and the eruption of permanent teeth which may cause pain and hence evasions. Wolf teeth may also cause problems and should be removed if troublesome. Vaccination. Horses should be injected annually, before a rest period, against equine influenza and biannually with an antitetanus booster. (Fig. 2.1 shows a detailed vaccination record.) The tetanus status of all horses in the yard should be known so that should an injury occur the vet will know whether or not a tetanus injection is necessary. Influenza vaccinations are compulsory for many competition horses; they are also important for the hunter which encounters large groups of strange horses at least once a week. Competitors should note that to gain entry to a racetrack stables the vaccination requirements are more stringent than for a showground and the certificate is checked for intervals between vaccinations right back to the primary injection. (See Chapter 10 for vaccination schedules.) Worming. Horses should be regularly wormed (Fig. 2.2) whether they are out at grass or stabled. It is very unfair to expect the horse to perform strenuous work while suffering from a worm burden. (See Chapter 12.) Checking. The horse must be checked over very thoroughly every working day for bumps, swellings and scratches. Any injury, no matter how trivial, should be noted and treated. Particular attention should be paid to the lower leg and hoof, looking for signs of heat, swelling and tenderness. Bathing. If the weather is reasonably mild the horse can be bathed (Fig. 2.3) from time to time during the training programme. This will help rid the coat of parasites, grease and scurf

< previous page

page_9

next page >

< previous page

page_10

next page > Page 10

Fig. 2.1 Vaccination record.

< previous page

page_10

next page >

< previous page

page_11

next page > Page 11

Fig. 2.2 Worming.

Fig. 2.3 Bathing.

< previous page

page_11

next page >

< previous page

page_12

next page > Page 12

which may be making the horse feel itchy. It will also improve the horse's appearance. A horse should not be washed unless it can be thoroughly dried. Soap or shampoo and plenty of warm water should be used all over the horse's body, except for the head which is washed last with clear water. Rinsing should be thorough, all traces of shampoo being removed as any left may cause a skin irritation. Excess water is then removed with a sweat scraper and the horse rubbed as dry as possible with a towel. Finally, the horse should be walked dry with a sweat rug on. Stabling A hunter brought up in August can be kept on a 'half-and-half system' for the first few weeks. This involves either keeping the horse in the stable during the day (to avoid the heat and flies) and turning out in the paddock at night, or just bringing in at night. Obviously, this is not practical for a horse brought into work during the winter. There are several advantages to the half-and-half system: It is always preferable to make any changes in the horse's routine gradually, allowing the digestive system to adapt to the hay and concentrate ration. A horse will be less exuberant if it spends some time in the field instead of shut in a stable. Young horses, particularly, may get very bored or upset at suddenly being confined in the stable for 23 hours a day. Thin-skinned Thoroughbred horses may actually lose condition out at grass if harassed by flies. One disadvantage is that once horses have had their hind shoes back on, it is unwise to turn them out together: even an irritable kick against flies may cause a nasty injury to another horse. Preliminary Work The preliminary work is designed to exercise the horse slowly for increasing lengths of time, and is accomplished by road work at the walk. This work tones up the muscles, tendons and ligaments, and is known as 'hardening the legs'. While not physiologically correct, this term sums up the role of preliminary work. Walking work is alleged to begin the process of turning the fat, acquired out at grass, into muscle. Strictly speaking, this process does not happen. The muscle system gradually develops; simultaneously,

< previous page

page_12

next page >

< previous page

page_13

next page > Page 13

the fat reserves of the horse are 'burned up' to provide energy for work. This process is more noticeable after faster work begins. The first few days' work can be done using a mechanical horse walker, long reining or by ride-and-lead. Commonly, with horses of reasonable temperament, riding is commenced from the outset. Any lunging should be undertaken with care as the horse's system is not ready for possible stress which can be created by working in small circles. Initially, it is best to start with 30 minutes a day on flat, easy ground, building up by 10 to 15 minutes a day until at the end of the first week the horse is walking for 1 hour. By the end of the second week, the horse should be up to 2 hours' walking work a day, including some hill work if possible. During the third week, some gentle trotting uphill can be included. Uphill work exercises the muscles and wind to a greater extent and has a less jarring effect on the front legs. The routine is much the same during the fourth week. Trotting periods can be longer, but never so long that the horse blows and sweats. Do not be tempted to cut the preliminary work short, particularly the walking work, no matter how boring it may become. It is essential to develop and harden the horse's muscle and reaccustom the horse to carrying a rider without overstressing the heart, lungs or legs. It is impossible to overemphasise the importance of this walking period. If early exercise is not done gradually and thoroughly, the risk of a horse becoming lame is much greater. During these walking sessions the horse must be active and working at the walk. On the other hand, a fresh horse straight up from grass may misbehave by jogging and pulling. The horse must be made firmly and quietly to walk. These high spirits must not be 'worked off' at a faster pace. Throughout all training, every aspect of horse and stable management is important, and it is particularly so at this time. For example, during the first fortnight the horse must be carefully checked every day for rubs, galls and injuries. The horse's skin is soft after its summer rest and is easily irritated by ill-fitting or badly cared for tack. Areas most at risk are the corners of the mouth and the girth and saddle region. A thick numnah and a soft girth or a soft girth-sleeve should be used. The saddle and girth areas can be hardened by bathing with salt water, methylated spirits, surgical spirits or witch-hazel. An added precaution is loosening the girth (not too much!) for the last 15 minutes of a ride, thus allowing the skin under the girth to cool gradually. When tacking up, the horse's front legs should be pulled

< previous page

page_13

next page >

< previous page

page_14

next page > Page 14

forward to stretch the skin into a comfortable position under the girth. Girths and numnahs should always be kept clean, being brushed or cleaned after use. Sponge-filled numnahs appear to cause sore backs more easily than others, just as sponge-lined boots irritate legs. As the majority of this work is road work, knee boots may be worn to protect the unfit horse which may be prone to stumbling. An unfit, weak-muscled horse may knock itself, particularly when starting trotting work. A careful eye should be kept on the legs, and brushing boots or Yorkshire boots fitted if necessary. Generally speaking, trotting should not be introduced until the horse is returning to the stable after a 2-hour walk as fresh as it left it. Trotting is very jarring to the horse's legs and initial trotting periods should be slow but active, short and preferably uphill. Four 200 metre trots would be adequate on the first day. The horse should have walked for at least 15 minutes so that it is warmed up before the first trot. After a few days' trotting, lunging can be introduced into the programme if desired. Initially, this should be not more than 6 or 7 minutes on each rein before or after the ridden work. Ridden schooling work can be included during the fourth week, consisting of large circles in walk and trot on both reins. Lunging and schooling will help prevent the horse getting bored or stale. Boots should be worn all round during this sort of work. Development Work By the end of the fourth week of road work, with some uphill trotting towards the end of the period, the horse should be ready to go on to the next stage of training and some cantering and suppling exercises can be incorporated. Horses will vary in the time taken to reach this stage. The best guide is how well the horse is coping with the uphill trotting: if its breathing at the top of the hill is fairly even and not strained, it is probably time to start canter work. Development training will vary, depending for which sport the horse is being got fit. The polo pony will be given some basic schooling and stick-and-ball work; the showjumper will be asked to jump small fences and combinations of fences; the racehorse will be cantering; the long distance horse will step up distance and speed; and the event horse will be given suppling exercises on the flat and over very small fences. All these aspects will be considered in separate sections later in the book. The traditional training methods were developed for the hunter, and it is the hunter that will be considered now.

< previous page

page_14

next page >

< previous page

page_15

next page > Page 15

The ground chosen for the first canter should be flat and good-to-firm, not soft and dotted with pot-holes. The overexuberant horse may be tempted to buck and go faster than desired, risking leg injury, so the rider should be prepared for this. Ask quietly for canter, and keep the horse's head up. If the horse is known to be strong, it should have on suitable tack. Canter work should be slow and short initially and gradually increased so that by the end of the sixth week three or four periods of steady cantering can be included in the exercise programme. At the end of each workout the horse will be blowing, but this should not be excessive and the horse should recover from it quickly during the trotting which should follow fast work. The exercise routine continues in much the same vein through the seventh and eighth weeks. This work is building up the horse's stamina (heart and lung endurance), with some uphill canter work being very beneficial. During this time (mid to late September) the horse is ready to go autumn hunting one or two short mornings a week. Make sure that the horse is not kept out too long, initially. When starting at 7 or 8 a.m., it is very easy to stay out until lunchtime and find that the horse has actually had a longer day than if it had been hunting. Although the horse may not have galloped and jumped, the number of hours it has been out of its box with a rider on its back will be very tiring for the semi-fit horse. Fast Work The hunter is rarely given any fast work during its exercise programme, October hunting usually providing the occasional 'pipe-opener' which prepares the horse for the beginning of the season. It is generally felt that the hunter hammers its legs quite hard enough from November to March/April out hunting, without galloping it in between hunting days! It is a good idea to school the horse over some cross-country or natural fences once or twice during October. The hunter may not have jumped a fence for 5 months, and it may avoid embarrassing moments to refresh the horse's memory. Following this sort of programme, the hunter should arrive at the Opening Meet ready to run for its life with a depth of fitness suitable to see it through the ensuing 5-month hunting season. During the Season Throughout the hunting season, days of sport will be interspersed with exercise days. Exercise on these days will follow much the same

< previous page

page_15

next page >

< previous page

page_16

next page > Page 16

pattern as the exercise given during the preliminary part of the training programme. The exercise given will, of course, vary depending on how hard the horse is hunted. A Hunt horse may do no more than one long, hard day a week or two half days a week, the latter being preferable. This horse will be kept fit by the hunting it does, and other exercise should be no more than 60 to 90 minutes' walking and a little trotting to keep it ticking over. Sunday will probably be a rest day, with the horse walked out to graze for 10 minutes in-hand. The day following hunting, exercise may be 30 minutes' walking to relieve any stiffness. A subscriber's horse may hunt only one day a week, that day being considerably less arduous than the Hunt horse's day. This horse would have a short walk the day after hunting (usually a Sunday) and possibly a day off midweek when it would be walked out in-hand for 10 minutes or so. For the remaining 4 days of the week it should have 60 to 90 minutes' exercise, including walking, trotting and cantering, as during the development phase of the exercise programme. This horse may also benefit from a short 'pipe-opener' the day before a hunting day, to clear its wind and prepare it for the next days' galloping. Horses may hunt twice a week, three days a fortnight or once a fortnight, and the exercise given to the horse between hunting days will vary accordingly. Horses hunting two days a week should be treated along the same lines as the Hunt horses. They are working very hard and will need the minimum of exercise to keep them fit. The horse hunting once every 2 weeks should be given some fast work once or twice during the non-hunting week or it will never reach peak fitness. This fast work could perhaps involve 750 to 1000 metres (half to three-quarters of a mile) at half speed in week 10 of the training programme, building up to 1500 metres (1 mile) at three-quarters speed by week 15 of the programme (mid-November). Barring accidents, a properly fed and exercised horse can stay at peak fitness throughout the whole of the hunting season, whether it is hunting 2 days a week or 1 day a fortnight. All horses will vary in the exercise needed to keep them in tip-top condition according to their temperament, type and the work they are doing. These factors must all be considered when planning the exercise regime for a hunter. The complementary aspects of nutrition and good management are discussed in subsequent parts of this book. The stag-hunting season lasts for 9 months of the year, which means that there is not actually enough time to let a horse down, give it a complete rest and get it properly fit again. If one is to hunt the whole

< previous page

page_16

next page >

< previous page

page_17

next page > Page 17

season, there are two alternatives. The first is to have two horses and treat them like foxhunters, working each for half the season; this, of course, may be too expensive. The other alternative is not to rough the horse off during the 3 months non-hunting but keep it ticking over so that it never loses its fitness and yet relaxes and gains condition. Many stag-hunting people hunt their horses off grass, supplemented with corn during spring and autumn hunting, which means that horses are more relaxed and keep their condition better than fully stabled hunters. The exercise programme will have to be adapted to suit each individual horse's and rider's requirements. Roughing off At the end of the hunting season the hunter is given a long summer's rest, traditionally being turned out to grass on 1 May. The hunting season seems to be finishing earlier and earlier due to modern farming pressures, with most Hunts now having their closing meets in March or April. A clipped-out concentrate-fed hunter should not be suddenly turned out at this time of the year when the weather is, to say the least, unpredictable and the grass growth uncertain. A gradual 'letting down' process should be followed, heading towards the resting period. Exercise should be reduced and, simultaneously, the concentrate ration cut down and the amount of hay fed increased. The number or weight of rugs should be decreased as the weather gets warmer, and the horse should be turned out into the paddock for a few hours a day as soon as the ground can stand it. At this point exercise can stop and the hind shoes can be removed. It is wise to keep front shoes on to prevent foot problems. The horse's summer coat should start to grow and it should start to look less lean and hard. By the end of April the horse should be out all day even if it is still coming in at night. It is worth taking time and trouble over the roughing-off period or the horse may get cold and lose condition which may take a long time to recover. During June and July the weather may be very hot and the horse may be pestered by flies, causing loss of condition, particularly in thin-skinned Thoroughbred types. It may be worthwhile stabling the horse during the day and turning it out at night if adequate shelter is not available. During the summer rest period, the horse must be wormed every 4 to 10 weeks, and checked daily for minor injuries. The farrier should trim the feet, and front shoes, if kept on, must be checked and changed when necessary. The field must be checked regularly to ensure that the fencing and water supply are safe and that there is no

< previous page

page_17

next page >

< previous page

page_18

next page > Page 18

sign of litter or poisonous plants or, indeed, any other hazard to the horse. Having got a horse to peak fitness during the hunting season, it seems a shame in many respects to let it get soft and flabby. Human athletes do not put on weight for the 3 months of the year and then struggle to get fit again. They may let themselves have a 'rest' by easing off slightly, but they always keep themselves ticking over. It puts a tremendous strain on the body's systems, heart, lungs, muscles and tendons to get unfit and then have to get fit again. However, horses that have hunted hard all season definitely need to rest and relax. A good compromise is to rough the horse off and turn it out but keep its shoes on and exercise it once or twice a week. This exercise could be 60 to 90 minutes' walk and trot, enough to keep the horse's back and girth area used to the saddle and the body systems used to working. This system may not suit everybody, but is much healthier for the horse.

< previous page

page_18

next page >

< previous page

page_19

next page > Page 19

PART II HOW THE HORSE WORKS

Introduction The horse's body can be thought of as being made up of several integrated systems, each system consisting of organs and tissues specialised for the specific tasks of that system. The systems are: The respiratory system. The circulatory systems of both blood and lymph. The locomotive systems of skeleton, muscles, tendons and ligaments. The systems of information and control; nervous, sensory and endocrine systems. The dental system. The skin. The urinary system. The digestive system. The first four systems are directly involved every time the horse is asked to work, and the respiratory, circulatory and locomotive system will be considered in detail. The dental and digestive systems have incidental effects on the fitness of a horse. If its teeth are sharp it will not eat properly, and if it fails to make good use of its food it will not thrive. A vital part of training a horse is feeding it correctly and the digestive system and nutrition are dealt with in Chapter 13. The skin is involved in heat loss and sweating which is vital to temperature control during exertion. It can be seen, therefore, that to get the best from the horse the trainer must understand the main systems and their functions.

< previous page

page_19

next page >

< previous page

page_21

next page > Page 21

3 The Respiratory System. Respiration is the process by which the horse takes oxygen into its body and also rids its body of carbon dioxide. This process takes place in every part of the body, the cells in the living tissue taking oxygen from the blood and giving back carbon dioxide. Anatomy The respiratory system consists of the airways of the head and neck and the lungs. Even in the healthy horse, the respiratory system may be a limiting factor for maximal performance. This means that even moderate dysfunction of the lungs may have a significant effect on the horse's performance. Within the Head and Neck The airways in the head and neck are shown in Fig. 3.1. The nostrils are the entrance to the respiratory system; the horse draws air in only through the nostrils and not through the mouth, and they can expand in order to take in more air. The nostrils lead to the nasal passages, where the air is warmed and foreign particles, e.g. dirt, are screened. Air then passes to the pharynx at the back of the throat. At the bottom of the pharynx is the soft palate which is overlapped by the epiglottis. Most of the time this overlapping shuts off the mouth and allows the free passage of air into the next part of the system, the larnyx. When the horse swallows, however, the epiglottis flips over the opening of the larynx, the soft palate moves up and food is admitted from the mouth into the pharynx and is then swallowed (Fig. 3.2). This mechanism is effective in separating the processes of breathing and eating, but makes mouth-breathing under stress very difficult for the horse.

< previous page

page_21

next page >

< previous page

page_22

next page > Page 22

Fig. 3.1 The airways of the head and neck.

Fig. 3.2 The operation of the epiglottis in the pharynx during breathing and swallowing. The air then passes to the larynx, which is a hollow box sitting on top of the trachea (or windpipe). It contains the vocal cords and controls the passage of air in and out of the trachea. The trachea runs from the larynx to the lungs, and consists of a large tube held open by rings of cartilage.

< previous page

page_22

next page >

< previous page

page_23

next page > Page 23

Within the Chest The structure of the lungs is shown in Fig. 3.3. The trachea divides into two bronchi close to the lungs, each bronchus supplying one lung. Within the lung they divide and subdivide to give small bronchioles. The bronchi are supported by rings of cartilage but the bronchioles are not. The bronchioles end in tiny sacs, which under the microscope look like bunches of grapes and are called alveoli. These sacs make up the body of the lung and make it feel like a smooth sponge to the touch.

Fig. 3.3 The structure of the lungs.

< previous page

page_23

next page >

< previous page

page_24

next page > Page 24

There are thousands of millions of alveoli, each about 0.3 mm across, giving a total surface area of several hundred square metres. Each alveolus is wrapped around by tiny blood vessels called capillaries (Fig. 3.4) and blood flows from the capillaries into the thin membranes of the alveoli. The air contained within the sacs is in such close contact with the blood that oxygen is able to move from the air in the alveoli into the blood, and carbon dioxide from the blood diffuses into the air in the alveoli and is removed when the horse breathes out.

Fig. 3.4 The alveoli, showing blood supply. The diaphragm (or midriff) separates the chest and lungs from the abdomen containing the digestive organs. It is a strong, dome-shaped sheet of muscle attached to the ribs and is used in breathing. Figure 3.5 shows how the lungs are arranged in the thoracic cavity (chest) of the horse in relation to the heart. Respiration The process of respiration can be broadly divided into two parts: (1) Breathing: this is the obvious and well known part of the process. (2) Tissue respiration: this is the aspect which is so important to the trainer of competition horses.

< previous page

page_24

next page >

< previous page

page_25

next page > Page 25

Fig. 3.5 The thoracic cavity, showing the relative positions of the lungs and heart: (1) heart, (2) coronary vessels, (3) aorta, (4) pulmonary veins, (5) pulmonary arteries, (6) vena cava, (7) trachea/windpipe, (8) bronchi, (9) oesophagus/gullet, (10) aorta, (11) pleural membrane, (12) lungs, (13) vertebra, (14) ribs, (15) back muscles, (16) skin. Breathing Breathing is the process of taking air down into the lungs and then expelling it from the lungs. The horse draws air in through its nostrils; air passes through the larynx, down the trachea and into the lungs. Here, oxygen passes from the air into the blood and carbon dioxide passes from the blood into the lungs, a process called gaseous exchange. The lungs are filled by the action of the dome-shaped diaphragm and the ribs. When the ribs

< previous page

page_25

next page >

< previous page

page_26

next page > Page 26

are pulled outward, the chest expands; simultaneously the diaphragm contracts, flattening the dome thus enlarging the 'box' in which the lungs are contained and drawing air in to fill the available space. This process is called inhalation. Breathing out, or exhalation, is achieved by the elastic recoil of the rib cage and lungs so that air is forced out. This may also be assisted by contraction of the abdominal muscles pushing the gut contents against the diaphragm. Thus air in the lungs is exchanged with air from outside and oxygen is brought to the alveoli. Oxygen and carbon dioxide are exchanged by a process of simple diffusion that is, by moving from the area of high to low pressure on each side of the thin alveolar membrane that separates air from the blood in the capillaries (see Fig. 3.4). Without oxygen, the muscles cannot function. Maximum performance of the horse depends on the effective passage of oxygen to the muscles and other tissues of the body. Oxygen is carried in the blood by means of the respiratory pigment haemoglobin in the red blood cells; this will be discussed further when dealing with the circulatory system. At rest, the horse has a repiration rate of 8 to 16 breaths per minute, the rate being higher for youngstock. Table 3.1 shows the resting respiratory rates for various other domestic animals and man. Table 3.1 Resting respiratory rates. Horse

812

Cow

1524

Sheep

1224

Goat

1220

Pig

1524

Dog

1930

Cat

2442

Man

1230

Tissue Respiration The respiratory rate is linked to the horse's gait. At gallop the stride rate equals the respiration rate and is described as locomotory-respiratory coupling. Step and respiratory frequencies average 110130 per minute with maximum values of 148 per minute. This means that the muscles of breathing and movement do not work against each other. As the galloping horse lifts the limbs, the head is raised, the gut

< previous page

page_26

next page >

< previous page

page_27

next page > Page 27

moves back and the horse breathes in. As the horse lands, the head drops, the gut moves forwards and the horse breathes out (Fig. 3.6). During recovery from fast work the horse's respiration rate may actually increase so that the horse takes in enough oxygen to pay off the oxygen debt accumulated during anaerobic respiration. This is known as post-effort hyperventilation and means that the time taken

Fig. 3.6 Energy sources for work.

< previous page

page_27

next page >

< previous page

page_28

next page > Page 28

for the horse's respiratory rate to return to normal will indicate how hard it has worked. However, the respiratory system also has a thermoregulatory role; in other words, horses recovering from work in hot and humid conditions will have higher respiratory rates and poorer recovery rates than horses in dry, cool conditions. The horse's respiration rate is an unreliable indicator of fitness. The second part of the respiratory process takes place when the oxygen being carried in the blood reaches the muscle tissue, and is called tissue respiration. This process produces energy from glucose in the blood or from fuel stored in the muscle cells as glycogen. To release the energy from the fuel supply requires oxygen which is carried in the blood; the process involves a complex series of reactions. Energy can be created by two methods of tissue respiration: (1) Aerobic respiration. (2) Anaerobic respiration. Aerobic (with oxygen) respiration takes place when the oxygen supply arriving in the blood is adequate to 'burn up' some of the glycogen in the muscle and to supply the energy demands of the animal. During this process, which is known as glycolysis, 1 unit of oxygen produces 36 units of energy. Carbon dioxide is also produced as a waste product; this is eventually expelled from the lungs during exhalation (Fig. 3.6). Anaerobic (without oxygen) respiration takes place when the energy demands of the animal are greater than can be supplied by the oxygen arriving in the blood. This situation is found in maximal exertion, e.g. sprinting. The muscle tissue then uses glycogen reserves to produce energy without the aid of oxygen. However, 1 unit of glycogen only gives 3 units of energy; thus anaerobic respiration is only one-twelfth as efficient as aerobic respiration (see Fig. 3.6). Anaerobic respiration causes a poisonous waste product called lactic acid to be produced. After exercise lactic acid is either eliminated as carbon dioxide and water, or converted in the liver back to glycogen. However, if the lactic acid is being produced in large amounts, as in the case of maximal exertion, e.g. galloping, it accumulates because the blood cannot remove it quickly enough. This build-up of lactic acid poisons the muscle cells and they can no longer contract. In practical terms, a horse cannot gallop indefinitely; tiredness begins to set in. Lactic acid contributes to fatigue and is a major limitation to athletic performance. It follows that the longer a horse can work aerobically, with no lactic acid production, before anaerobic respiration and lactic acid

< previous page

page_28

next page >

< previous page

page_29

next page > Page 29

build-up occur, the longer it can carry on before fatigue stops work. This describes, in physiological terms, the basic aim of getting a horse fit, and the words 'aerobic' and 'anaerobic' will be used frequently in the course of this book. The Effects of Training Adaptations to training may differ according to: age previous training intensity and duration of work breed type of training programme. Both rider and trainer are strongly aware of the necessity of knowing that a horse is 'right in its wind', and much of a training programme is devoted to getting a horse fit and clear in its lungs. A fit horse is able to do a lot more work than an unfit horse before it starts to blow. Once blowing, a fit horse's breathing rate will return to normal more quickly than an unfit horse's. Training accomplishes the following changes in the respiratory system: (1) Alveolar recruitment. During periods of inactivity, the tiny air sacs in the lungs become blocked by mucus and other debris. Exercise causes this debris to be brought up out of the lungs. This is the reason for an unfit horse occasionally being 'thick in its wind' and having a slight discharge of mucus from its nostrils when it is first brought into work. This clearing of a horse's wind is called alveolar recruitment, and results in the horse having a larger useful lung capacity and hence a greater ability to get oxygen into the blood. (2) Pulmonary capillarisation. The tiny blood vessels or capillaries that surround each alveolus respond to the increased oxygen demands of the exercising horse by increasing in number, or proliferating. Thus there is not only a greater area of blood vessels across which gaseous exchange can take place, but also a greater area of lung tissue and hence more oxygen arriving at the tissues. (3) Muscular development. The muscles of the diaphragm and chest which control breathing may also get stronger as the exercising horse uses them more.

< previous page

page_29

next page >

< previous page

page_30

next page > Page 30

(4) Nostril size. There is a school of thought that believes that nostril size may be limiting to air intake. Horses bred for performance, e.g. Arabs and Thoroughbreds, have nostrils which are capable of flaring widely when the horse is worked. Certainly, any restriction in the airways will inhibit performance. Studies indicate that the adaptations of the respiratory system occur rapidly when the intensity of training is sufficient but these changes are highly reversible and a 3-week rest will return the horse to its pretraining state. Despite these effects, a horse's wind must be basically sound if it is to be trained to maximum fitness. A defect such as roaring or whistling, or an allergy, may affect the wind in such a way that the afflicted horse will never be able to reach peak fitness. This does not imply that such horses are not capable of hunting or eventing, but it will not be possible to get them as fit as if there were no defect. The object of the horse's training programme is to teach the body to use more oxygen. The more oxygen the body can use, the more work can be done aerobically: the 'aerobic threshold' of the animal has been increased. Thus the onset of anaerobic respiration is delayed, and hence the production of lactic acid and the onset of fatigue are postponed. Anaerobic respiration is a 'spend now, pay later' process: the energy supplies used have to be replaced, and this process requires oxygen. In effect, an 'oxygen debt' has been created, which has to be paid off after strenuous exercise this is why the horse goes on blowing after it has pulled up. The energy produced during tissue respiration may not be needed immediately. This energy is stored in a remarkable chemical molecule called adenosine triphosphate (ATP). The stored energy is released when adenosine triphosphate is converted to adenosine diphosphate (ADP) (Fig. 3.7).

Fig. 3.7 High energy compounds.

< previous page

page_30

next page >

< previous page

page_31

next page > Page 31

4 The Muscle System Muscle does the work that drives the horse, and part of getting a horse fit consists of muscle development or 'muscling-up'. Different shapes and makes of horses develop muscle in varying places: the staying Thoroughbred tends to be lean and rangy, while the sprinting Thoroughbred and the Quarterhorse are blocky and more heavily muscled. In order to understand why these differences arise and how to develop a horse's muscles to maximum fitness, it is important to understand a little of the structure and function of muscle tissue. In general, muscles are divided into three major groups: (1) Smooth muscle is found in the walls of hollow organs such as the digestive tract. (2) Cardiac muscle is found only in the heart. (3) Skeletal or striated muscle moves the skeleton, and it is this muscle that the rider is concerned with developing. Skeletal Muscle. Skeletal muscle cells are specialised for the function of contraction. Each skeletal muscle is made up of many millions of elongated cells called fibres, or myofibrils. These lie parallel to one another and are bound together and to the tendons at each end of the muscle by connective tissue (see Fig. 4.1). Muscle cells contain stores of glycogen and the enzyme systems for the breakdown of the glycogen to give energy for muscle contraction. The cells also contain the red muscle pigment myoglobin which, like haemoglobin, can bind oxygen to itself and so acts as an oxygen store. Muscle contraction is brought about by components of the muscle fibre sliding over one another, leading to a shortening of the muscle (Fig. 4.2). This contraction requires energy. The energy supply is maintained by the 'powerhouses' of the cell, tiny structures called mitochondria, and the fuel for these powerhouses is obtained from the breakdown of glucose. Energy can also be obtained from the

< previous page

page_31

next page >

< previous page

page_32

next page > Page 32

Fig. 4.1 The structure of skeletal muscle. breakdown of free fatty acids, which are present in the blood or stored in the muscle. Muscles receive nerve messages which stimulate contraction. They also have a continuous blood supply which brings the oxygen and other nutrients necessary for producing the energy for contraction, and takes away carbon dioxide and other waste products. During strenuous activity, the blood supply to muscles can be increased 60-fold, indicating the importance of the muscles receiving large supplies of nutrients. This also indicates the benefits of training so that each system can operate at maximum efficiency. Muscle Fibre Types Recently, the knowledge of the composition of muscle and how various muscle fibres are used during exercise has increased dramatically. This knowledge has been helped by using a muscle

< previous page

page_32

next page >

< previous page

page_33

next page > Page 33

Fig. 4.2 Muscle contraction and relaxation. biopsy technique, which is a safe painless way of taking tiny samples of living muscle for study. The skeletal muscle of the horse is similar to that of all mammals, but selective breeding has resulted in horses with specialised muscle characteristics; for example, there are the powerful draught breeds, the endurance breeds such as the Arab, and the speed merchants like the Thoroughbred. The horse possesses different types of skeletal muscle fibres. Initially, muscle types can be identified by colour: red muscle is associated with long-term or endurance work, e.g. leg muscles of fowl. The dark colour reflects the high myoglobin content and thus the greater ability of the muscle to use oxygen, i.e. it is high oxidative muscle. White muscle is associated with power, e.g. the breast muscles of fowl, which are the powerful muscles used for flying. This muscle has a lower capacity for using oxygen, i.e. it is low oxidative muscle. More specifically, muscle can be divided into two major types depending on its contractile properties: (1) Slow twitch muscle has a slower contraction time and a greater capacity for using oxygen and can therefore work continuously.

< previous page

page_33

next page >

< previous page

page_34

next page > Page 34

(2) Fast twitch muscle has a faster contraction time. Two types have been identified according to their ability to use oxygen: (a) High oxidative, fast contraction muscle, but which is also able to use oxygen and therefore to work for long periods. This makes it very important in the horse required to sustain speed over long distances. (b) Low oxidative muscle used for galloping and fast acceleration. This muscle fatigues rapidly. Muscle Fibre Recruitment During most muscular contractions, it is not necessary for all the muscles to generate their maximum strength: not all the fibres have to be stimulated. There is an orderly selection of muscle fibres depending on the amount of exertion: for walking and standing, only slow twitch fibres are used; as the speed increases, fast twitch fibres of the high oxidative type are recruited, and it is only during rapid acceleration and jumping that the fast twitch fibres of the low oxidative type are used. Most muscles contain a mosaic of these three skeletal muscle fibres spread uniformly throughout the entire muscle. The presence of all three fibre types allows a wide range of responses, and the muscle is able to respond to the various demands put upon it (Fig. 4.3). Distribution of Fibre Types It has been discovered that elite marathon runners have a very high proportion of slow twitch fibres, while sprinters have a lower proportion of slow twitch fibres and more fast twitch fibres. This difference appears to be determined genetically, i.e. marathon runners are born with the potential to run long distances. A similar trend can be seen in different breeds of horse. Even in the untrained state, the sprinting specialist, the Quarterhorse, has a greater proportion of fast twitch fibres than the Thoroughbred or Standardbred horse (Table 4.1). Another feature of the Quarterhorse is that the fast twitch muscle fibres have a greater diameter, i.e. they are thicker and are thus able to generate more power. In those horses well adapted for endurance work, all the muscle fibres are of similar size. This allows blood to reach all the fibres, the blood bringing with it adequate supplies of oxygen and nutrients (Fig. 4.4).

< previous page

page_34

next page >

< previous page

page_35

next page > Page 35

Fig. 4.3 Skeletal muscle fibre types: (a) slow (Type I) and fast (Type II) fibres, and (b) Type I high-oxidative fibres (ST). Type II high-oxidative fibres (FTH) and Type II low-oxidative fibres (FT). (D.H. Snow, 1983, pers. comm.)

< previous page

page_35

next page >

< previous page

page_36

next page > Page 36

Table 4.1 Slow twitch fibres in different breeds of horse (from the middle gluteus muscle). % Quarterhorse Thoroughbred Arab Standardbred Shetland Pony Donkey Endurance horse Heavy horse

7 13 14 18 21 23 24 28 31

Fatigue When getting a horse fit, the aim is to be able to work the horse for longer before it gets tired; in other words, to delay the onset of fatigue. Fatigue is the inability of a physiological function to continue at that level a horse cannot gallop indefinitely. If the horse is not allowed to slow down, exhaustion will eventually set in exhaustion being the complete inability to maintain exercise. It is important to consider the causes of fatigue in order to be able to train a horse and avoid exhaustion. There are four major factors contributing to the onset of tiredness: glycogen depletion lactic acid build-up dehydration and heat stress (hyperthermia) lameness. The last two factors will be discussed later. Glycogen Depletion During work, the different muscle fibre types are brought into use in turn and are progressively depleted of their glycogen stores. A horse performing mainly aerobic (with oxygen) exercise, e.g. prolonged low speed endurance work, will be using a majority of slow twitch fibres and a few fast twitch high oxidative fibres. Oxygen can be brought by the blood to the fibres fast enough to supply the energy demands of

< previous page

page_36

next page >

< previous page

page_37

next page > Page 37

Fig. 4.4 Muscle biopsies from middle gluteal of three 2-year-old Thoroughbreds showing marked differences in fibre cross-sectional area (reacted for succinic dehydrogenase activity (D.H. Snow, 1983, pers. comm.).

< previous page

page_37

next page >

< previous page

page_38

next page > Page 38

the muscle because the horse is not working hard. However, glycogen stores will eventually be used up; there will be no source of energy for the muscle fibres and they will no longer be able to contract. (Remember that oxygen and glycogen are needed to produce energy for contraction during aerobic respiration.) Once all the glycogen has been depleted from muscle cells, it takes 48 to 72 hours to replace it. Lactic Acid Build-up As the speed of the work increases, fast twitch low oxidative fibres will be recruited. The blood becomes unable to supply oxygen in large enough amounts for aerobic respiration to take place, and anaerobic (without oxygen) respiration will commence. The by-product of anaerobic respiration, lactic acid, will be produced in the muscles. At a fast gallop, the lactic acid will be produced at such a rate that the blood cannot carry it away from the muscles quickly enough, resulting in a build-up of lactic acid in the muscles. These acid conditions prevent the muscle fibres from functioning properly; eventually they cut out and are unable to contract, and the horse has to slow down. In man, the lactic acid build-up is associated with pain. This could also be true in horses, in which case a horse's performance may also depend on how much pain it feels and how willing it is to withstand that pain. However, the horse is able to tolerate much higher levels of lactic acid before tiring than the human athlete, indicating the horse's adaptation as an elite athlete. Once the lactic acid has been removed from the muscles, exercise can be continued at similar workloads think of how the flagging hunter recovers after a check. Removal of the lactic acid is more rapidly accomplished if mild exercise is continued. The racehorse would benefit from being cooled off at a slow trot after a gallop, because of the maintenance of a good blood supply to the muscles to carry the lactic acid away. There may also be long-term advantages in the lactic acid being removed quickly there may be less stiffness in the muscles next day, which is important in the three-day event horse which has to showjump the day after completing a strenuous cross-country course. Giving a horse sodium bicarbonate, which is alkaline, to neutralise the acid may prolong the time to fatigue at high workloads. Present opinion suggests that a dose of 0.30.4g/kg sodium bicarbonate given approximately 2 hours before an event may be beneficial. Larger doses, however, may cause problems. The administration of frusemide with sodium bicarbonate, however, will induce metabolic alkalosis and should be avoided. Sodium bicarbonate should not be given to

< previous page

page_38

next page >

< previous page

page_39

next page > Page 39

long distance horses under any circumstances due to the loss of electrolytes through sweating over a long period of time. Lactic acid, then, is a limiting factor in the performance of the horse; therefore any training programme must aim to delay the buildup of lactic acid. The Effects of Training Muscle is able to adapt during training to the varying demands placed upon it, showing both immediate and longterm responses. Metabolic Changes Aerobic Enzymes. Training causes an increase in aerobic enzyme activity and an increase in high oxidative fibres. The major changes probably occur within the first 2 months of training, with gradual increases being made over the next couple of years. Associated with this increase in aerobic enzyme activity is an increase in the number of mitochondria and an increase in capillarisation. Increased aerobic capacity leads to more efficient generation of ATP, delaying the onset of fatigue. Metabolic changes resulting from training will carry on for several weeks after training has ceased. Glycogen Glycogen is found at higher levels in horse muscle than most other species; hence the sweet taste of horse meat. Training appears to produce an increase in glycogen levels. This may also be due to the higher level of soluble carbohydrate found in the diets of most horses in training. The muscle develops greater ability to store glycogen. Anything that slows down the rate of breakdown of glycogen or increases its concentration in the muscle will prolong the time the horse can work before fatigue sets in. Training also encourages the use of free fatty acids as an energy source. This is known as 'glycogen sparing' as more glycogen is left for emergency use. Human marathon runners are able to manipulate their diet before a race so that the concentration of glycogen in the muscles is very high, but use of these techniques in horses is debatable because of the chance of azoturia resulting from high glycogen levels.

< previous page

page_39

next page >

< previous page

page_40

next page > Page 40

Buffering Capacity The ability of the muscle to neutralise the acid produced during exercise will affect the onset of fatigue. The Thoroughbred has been found to have a very high buffering capacity compared with humans. The practice of giving a horse sodium bicarbonate solution several hours before a race is an attempt to increase the buffering capacity and hence improve the horse's performance. Fibre Type Alteration In the horse, training increases the oxygen-using capacity of the fast twitch muscle fibres, i.e. low oxidative fibres are transformed to high oxidative fibres. Fibre Size High oxidative fibres have a smaller cross-sectional area. This allows faster passage of oxygen into the cell and more rapid removal of waste products such as carbon dioxide. However, with sufficient aerobic training the proportion of muscle occupied by high oxidative fibres is greater because they increase in number. The rate at which some of these changes are reversed once the horse is no longer in work is not clear; varying results have been obtained and it is an area which needs further investigation. However, it would appear that metabolic changes can be sustained for several weeks. This means that once the horse has reached peak fitness, the amount of work it needs to maintain muscle fitness may be reduced. This would be useful, both mentally and physically. Mitochondria Training increases fuel availability to muscle fibres by encouraging more mitochondria (the powerhouses where energy is generated) and more enzymes for the breakdown of glycogen and free fatty acids. Blood Supply The blood supply is increased as the capillaries feeding the muscle proliferate. Also, in the horse the spleen acts as a blood reservoir. There is no equivalent action in man: thus training human and equine athletes are parallel but not identical sciences.

< previous page

page_40

next page >

< previous page

page_41

next page > Page 41

The Training Programme A muscle fibre can only adapt to the demands made of it in competition if it has received suitable stimuli during training. Thus one can only get a favourable effect from training if the programme includes the same type and similar intensity of exercise as is met during competition. If speed is required, sufficient sprinting should be included to recruit the necessary fibres for power and acceleration. If the competition involves endurance work at varying speeds, prolonged exercise at these levels is needed to increase the oxygen-using capacity of the muscles. This means that the time until the onset of fatigue is delayed, and the horse can work at higher speeds before anaerobic metabolism and the build-up of lactic acid begin.

< previous page

page_41

next page >

< previous page

page_42

next page > Page 42

5 The Circulatory System The circulatory system consists of a muscular pump the heart and a network of blood vessels for carrying blood throughout the body. Functions of the Circulatory System. The basic function of the system is to transport essential substances round the body, including: (1) Oxygen from the lungs to all body cells. (2) Carbon dioxide from body cells to the lungs. (3) Nutrients from the gut to body cells. (4) Waste products from body cells to the kidneys. (5) Hormones from glands to body cells. (6) Antibodies, the body's defence force, to sites of attack. (7) Heat, evenly distributed from the body core to the skin. Anatomy of the Circulatory System The Heart The heart (Fig. 5.1) is a hollow muscular pump at the centre of the circulatory system, and consists of four chambers. The upper chambers of the heart are the right and left atria which act as receiving chambers for blood coming from large veins. The lower chambers are the right and left ventricles which act as pumping chambers, pushing the blood into the large arteries leaving the heart. Due to this pumping action, the ventricles are larger (more muscular) than the atria, the left ventricle being the largest because it pumps blood throughout the body. Circulation of Blood through Heart and Lungs The circulation of the blood is illustrated in Fig. 5.2. The vena cava brings deoxygenated blood back from the body to the right side of the

< previous page

page_42

next page >

< previous page

page_43

next page > Page 43

Fig. 5.1 The heart.

Fig. 5.2 The heart and circulation.

< previous page

page_43

next page >

< previous page

page_44

next page > Page 44

heart. Deoxygenated blood has had the majority of its oxygen removed and replaced by carbon dioxide in the tissues (as described in Chapter 3). The blood is collected in the right atrium and passes into the right ventricle. The right ventricle contracts and sends blood into the pulmonary artery which leads to the lungs. In the lungs, carbon dioxide is exchanged for oxygen, i.e. the blood is oxygenated and returned to the left side of the lung along the pulmonary vein. Blood enters the left atrium, then passes into the left ventricle. When the left ventricle contracts, blood is pushed into the aorta (the main artery of the body). Throughout this sequence, valves in the heart prevent backflow of blood. Circulation of Blood through the Body Oxygenated blood is pumped away from the left ventricle via the aorta and distributed under pressure throughout the body by a branching system of arteries and arterioles (small arteries). These vessels have thick muscular walls which can control the amount of blood that flows at any time, thus helping maintain blood pressure. The horse owner is aware of arteries as being the places where the pulse is taken, e.g. under the jawbone, under the dock, inside the elbow and below the hock. These are all places where an artery passes over a bone close to the skin and a pulse of blood flowing through the vessel can be felt. This pulse corresponds to the beating of the horse's heart. As the branches become smaller, the oxygenated blood passes through a system of tiny vessels called the capillary network. Here water, oxygen and other nutrients carried in the blood pass through the walls of the capillaries into the body tissue cells, in exchange for waste products from the cells which are carried away in the blood. The tiny capillaries then merge, forming larger and larger veins which carry deoxygenated blood back to the heart. Veins have thin walls with very little muscle. In order to prevent backflow of blood, the walls of veins have a series of one-way valves (Figs 5.3 and 5.4), and this allows muscle contractions from normal body movements to help push blood back to the heart. (The swelling of a horse's legs when exercise is restricted is due to a lack of muscular activity, and hence an inhibition of return of blood to the heart and fluid accumulation in the legs.) The large vein of the body, the vena cava, then returns all the deoxygenated blood to the right side of the heart. The circulation of blood through the body is called the 'systemic circulation' and that through the lungs the 'pulmonary circulation',

< previous page

page_44

next page >

< previous page

page_45

next page > Page 45

Fig. 5.3 Cross-section through a one-way valve in the wall of a vein.

Fig. 5.4 Valves of a vein, showing the pumping action of adjacent muscles.

< previous page

page_45

next page >

< previous page

page_46

next page > Page 46

and together they make up the characteristic double circulation of the horse. The Effects of Training and Exercise The resting heart rate of a horse is normally 36 to 42 beats per minute that of a fit horse may be as low as 26 beats per minute and reaches a maximum of 240 per minute when galloping. As the aim of training is, as has already been stated, to get oxygen to the muscle cells and to remove waste products as efficiently as possible, the heart and circulation have a vital role to play. During exercise, the muscles contract more frequently; their energy requirement (i.e. the oxygen requirement of the body) is greater. Thus the immediate effects of exercise are: increased heart rate increased respiratory rate. The increased heart rate causes a greater cardiac output more blood is pumped round the body in a given time. The higher respiratory rate supplies the blood with more oxygen. In an unfit horse, these increases cannot be sustained for long. The Effects of Training (1) Increased heart size. Like any other muscle in the body, the horse's heart responds to exercise by developing and getting bigger (Fig. 5.5). The average size of the horse's heart is about 4 kg (9lb); the trained heart can weigh 5.5kg (12lb) and pump 1.7 litres (3 pints) of blood at each beat. The heart of the famous racehorse Eclipse weighed over 6.5kg (14lb). The trained horse galloping sends its blood once round its body in just over 5 seconds, emphasising the importance of a healthy heart and circulation. (2) Capillarisation. Training increases the number of blood capillaries in the muscles capillarity can increase by up to 50% (Fig. 5.6). This means there is a greater surface area of blood vessels through which oxygen can be supplied to the muscle tissues. If capillaries are not being used, as in the unfit horse, they tend to 'dry up'; training causes them gradually to come back into use. It has been estimated that it takes up to 3 years to realise the full potential of the circulation when bringing a totally unfit horse into work.

< previous page

page_46

next page >

< previous page

page_47

next page > Page 47

Fig. 5.5 The effect of exercise: increased heart size.

Fig. 5.6 The effect of exercise: capillarisation of muscles. These internal changes in the heart, circulation and respiratory system show themselves to the rider as the horse gets fitter by: • a slower resting heart rate • a less dramatic increase in heart rate and respiration rate for a given amount of exercise • a quicker recovery rate (the time taken for heart rate and/or respiration rate to return from working levels to resting levels). In simple terms, the horse can work for longer without becoming distressed or fatigued.

< previous page

page_47

next page >

< previous page

page_48

next page > Page 48

Monitoring Heart Rate Heart rate can be monitored in several ways by the rider/trainer or by the veterinary surgeon. (1) Stethoscope. This can be used by the rider to determine heart rate, or by the vet to detect any abnormalities in heart sounds (this is discussed in the next section). (2) Pulse. As mentioned previously, the pulse is felt where an artery passes over a bone close to the skin, the most commonly used site being the facial artery under the cheek bone. This is a simple way for the rider or vet to assess the heart rate of an animal. (3) Heart rate monitor. This is a machine which records the heart rate instantaneously by means of electrodes pressed against the skin (figs 5.75.9). A digital readout display is attached to the rider's wrist or around the horse's neck so that heart rate can be read at any time during exercise. Sophisticated versions are considered invaluable for interval training, but the price of these models is high; they are now available in the U.K. (4) Electrocardiogram. The vet can examine the heart using an electrocardiogram (ECG), which is a recording of the elec-

Fig. 5.7 The heart monitor numnah in position.

< previous page

page_48

next page >

< previous page

page_49

next page > Page 49

Fig. 5.8 The digital readout strapped to the wrist. trical activity caused by nerve impulses in the heart muscle. This is a very specialised technique which has been used to relate the horse's heart size to performance potential. Assuming that a larger mass of heart muscle requires a longer time to contract, a specific portion of the ECG trace is thought to indicate the heart size of the animal, and is called the 'heart score'. The theory is that the larger the heart in relation to the horse's size, the better able it will be to meet the oxygen demands of the muscles during exercise. A study in Australia found that racehorses with the best performances had higher than average heart scores, i.e. bigger hearts. It is suggested that heart score can be used to indicate superior athletic ability. A slower resting heart rate also indicates a larger heart. The bigger heart has to do less work to pump the same amount of blood; thus a fit horse with a well-developed muscular heart has a slower resting heart rate than an unfit horse. It must be remembered that heart rate can vary considerably between individual horses, and each rider should make a conscientious effort to know the resting heart rate for their own horse. Once this is established, the heart rate can be used to monitor the horse's progress during a conditioning programme.

< previous page

page_49

next page >

< previous page

page_50

next page > Page 50

Fig. 5.9 The monitor in position. The Heartbeat The actions of the heart during one complete heartbeat make up the 'cardiac cycle'. Simultaneously blood enters the right atrium from the body and the left atrium from the lungs. The atria contract when they are full, opening the valves and thus allowing blood to flow into the relaxed ventricles. When nearly full the ventricles begin to contract, closing the valves to the atria. While the ventricles contract blood is forced out of the heart, through non-return valves, to the body and lungs. These are the diastole and systole actions of the heart, 'diastole' being the relaxation (dilation) of a chamber just before and during its filling and 'systole' the contraction of a chamber in the process of emptying. When the heart beats it makes sounds. There are actually four heart sounds, but only two are loud enough for the average ear to distinguish.

< previous page

page_50

next page >

< previous page

page_51

next page > Page 51

Commonly known as 'LUBB-dup', they mark the opening and closing of valves during the sequence of heart action. The 'LUBB' sound marks the point in the beat when the valves between the atria and the ventricles are closing and the artery valve exits are opening to permit the flow of blood to the lungs and body. The crisp-sounding 'dup' occurs as the interchamber valves open and the arterial valves close. The heart beats because of electrical impulses that come from a natural built-in pacemaker. Signals for controlling heart rate come from the brain via nerves. At regular intervals the pacemaker sends out an electrical impulse which causes a wave of contraction in the heart muscle, and the heart goes through an orderly series of systoles and diastoles as described above. The silent period in the heartbeat occurs when the heart is filling with blood. The sounds the heart makes can indicate the health of the heart. Heart Murmurs and Arrythmias. Unlike human heart attacks, most sudden equine deaths result from rupture of the aorta, the main artery which carries oxygenated blood from the heart. The human heart-attack victim collapses because the muscle of the heart wall has had its blood supply cut off; the coronary artery has been blocked, e.g. by a clot, and this causes part of the heart muscle to die. The heart is unable to beat, resulting in collapse. Although horses rarely die through cardiac problems, normal resting horses' hearts often skip beats, and fit, functional horses may develop loud variations of normal heart sounds. Fortunately, however, the majority of horses whose hearts make odd sounds or beat erratically function quite well. It has been suggested that over half of all normal healthy horses may have innocent murmurs and benign arrhythmias. Murmurs A murmur is an unusually loud or odd sound that can be heard during what would normally be a silent period in the cardiac cycle. Murmurs are the most common type of abnormality found during routine examination, and may be described as whistling, harsh, blowing, machinery-like, buzzing, squeaking, high-pitched, cooing or hissing they all indicate turbulence in blood flow through the heart. Some are caused by changes in the pumping action or in the consistency of the blood, but these are not generally serious. Serious murmurs result from structural flaws in the heart.

< previous page

page_51

next page >

< previous page

page_52

next page > Page 52

Fit athletic hearts are prone to murmur because training builds up heart muscle so that the heart pumps more blood with each stroke. Thus the resting heart rate is slower and the resulting rush of blood is louder than normal. Technically this sound is a murmur, but functionally it is a normal noise for the heart. Other murmurs that occur in horses with normal hearts can be explained by changes in blood circulation brought on by fever, stress and anaemia. Increased body temperature and stress speed up heart rate and blood flow, which can lead to abnormal sounds in the cardiac cycle. Anaemia encourages odd heart sounds because the number of red blood cells is reduced, altering the consistency of the blood. The turbulence of the thinner fluid passing through the heart is heard as a murmur. Most such murmurs produced by normal hearts will subside as the horse regains health. Murmurs can arise when the valves in the heart, which separate the chambers, deteriorate with wear and tear (Fig. 5.10). The valves become shortened and thickened so that they close imperfectly and blood can leak through. This leaking blood makes a noise heard through the stethoscope as a murmur. Older horses often manage quite well with 'loud valves', but it is rare for these older horses to be pushed for maximum performance, which is when valve problems could show up.

Fig. 5.10 Normal and faulty heart valves

< previous page

page_52

next page >

< previous page

page_53

next page > Page 53

Listening to a horse's heart sounds both at rest and after exercise can indicate the severity of a murmur. The two main points the vet will listen for are: (1) The timing of the murmur in the cardiac cycle. (2) How the murmur reacts to exercise. Murmurs that disappear or fade with exercise are not usually serious. Low pitched 'blowing' murmurs that occur with contraction (following the 'LUBB' sound) are usually the harmless sounds of the rush of blood ejected from a larger than average heart. Loud heart murmurs that hide the normal crisp valve sounds (the 'dup') usually indicate a valve malfunction. Flow sounds during the heart's rest period indicate that blood is leaking back from the exit arteries. Arrythmias Occasionally the resting horse's heart will skip a beat. In a fit horse, this is probably a way of regulating total blood supply to the tissues. Even though the beat is as slow as it can go, the heart is still ejecting more blood per minute than the horse's needs at rest. The solution is to miss a beat occasionally. When the horse is exercised and the demand for blood increases, the heart will beat regularly. 'Random arrythmia' is an irregular flurry of rapid beats. When this occurs the heart is not functioning efficiently: a slow steady stroke allows refill time, but rapid irregular beats do not. This flutter occurs due to a failure in the nervous control of the heartbeat. The nerve centre in the heart which stimulates contraction (the pacemaker) may have had to move because the original site has been damaged in some way, e.g. as a result of inflammation. Additional pacemakers may have arisen which compete with the original pacemaker, and thus random signals could be causing the heart to contract before the chambers are filled with blood. The most common arrythmia is called 'atrial fibrillation', and occurs in the upper chambers of the heart. During exercise, the fibrillating heart may beat up to 260 times per minute, as compared to a normal maximum of 240 times per minute. A sudden drop in the horse's performance is one sign of the onset of this condition. Treatment with drugs combined with rest may return the heart beat to normal. Heart muscle inflammation brought on by infective damage may cause changes in the pacemaker, and may follow an attack of equine influenza. Although it would appear that a number of horses die with heart

< previous page

page_53

next page >

< previous page

page_54

next page > Page 54

abnormalities, very few die because of them. Murmurs and arrhythmias are often conditions that a horse can live with, provided it is not expected to perform at very high levels. Generally speaking, the horse's heart copes with the demands put on it very well. The Blood Blood is the vital transport medium connecting the heart and the lungs to the rest of the body. It carries nutrients absorbed from the digestive tract to all tissues of the body. Oxygen is transported from the lungs to the tissues, and carbon dioxide is carried back from the tissues to the lungs. The blood carries waste products from the cells to the kidneys for excretion. Hormones and factors by which the body fights disease are also carried in the blood. The clotting ability of blood helps ensure that large quantities of blood are not lost through injury. In addition, blood helps control body temperature by transporting heat from deep structures to the surface of the body. The Structure of the Blood Plasma The composition of the blood is illustrated in Fig. 5.11. It consists of a straw-coloured fluid called plasma in which all the cellular components of the blood are suspended. These are red cells, white cells and platelets. Plasma contains fibrinogen which aids clotting of blood, and serum which contains water, proteins, glucose, lipids (fats), amino acids, salts, enzymes, hormones, antigens, antibodies and urea. The proportion of cells to plasma, known as the 'packed cell volume' (PCV), is in the range 31 to 55%, 40% being an average value. Red Blood Cells Red blood cells or erythrocytes originate in the bone marrow. They are tiny cells containing haemoglobin, the respiratory pigment. Their job is to carry oxygen: when exposed to high concentrations of oxygen, e.g. in the lungs, haemoglobin takes up oxygen and carries it as oxyhaemoglobin. In the tissues there is very little oxygen; here the oxyhaemoglobin releases its oxygen so that the tissues can use it to produce energy.

< previous page

page_54

next page >

< previous page

page_55

next page > Page 55

Fig. 5.11 The components of blood.

< previous page

page_55

next page >

< previous page

page_56

next page > Page 56

Fig. 5.12 The red blood cell. Red blood cells are structured with thick edges and thin centres, providing a larger surface area for oxygen exchange (Fig. 5.12). These cells are continually being worn out and replaced. Worn out cells are destroyed in the liver, and products which cannot be used again are excreted in the bile. A Thoroughbred-type horse normally has 9 to 12 million red blood cells per cubic millimetre of blood. White Blood Cells There are five kinds of white blood cells or leucocytes: neutrophils and basophils, eosinophils, monocytes and lymphocytes (Fig. 5.13), their main function being to defend the body against disease. Some, such as neutrophils, are most active in defence of acute infection, while others, such as monocytes, are most active in the face of less acute infections. Leucocytes are carried by the blood to general locations of infection and then can move to the actual site of the infection. Leucocytes fight infection by engulfing the invading bacteria and digesting them. This material, with dead tissue, constitutes pus.

< previous page

page_56

next page >

< previous page

page_57

next page > Page 57

Fig. 5.13 Types of white blood cell. Blood Proportions Each type of cell is present in the blood in characteristic numbers. These numbers can be used to assess the health and fitness of a horse when a blood test is taken, as will be discussed in more detail later. The volume of blood present in the horse is about 10% of its body weight, i.e. a typical 500 kg (0.5 ton) horse has about 45 litres (10 gallons) of blood. About 60% of this is water, and the blood plays a vital role in regulating the fluid balance in the horse's body. This can be of importance in a performance animal that sweats heavily. Not all the 45 litres of blood is circulating round the horse's body all the time. Some blood is stored in the spleen, an organ situated near the stomach which acts as a reservoir of blood. Blood is released from the spleen in times of stress, e.g. during exercise. The release of these splenic reserves can alter the values obtained in a blood test dramatically.

< previous page

page_57

next page >

< previous page

page_58

next page > Page 58

The Effects of Training On the Blood. Red Blood Cell Number When considering the horse as an athlete, great importance is placed on the number of red blood cells because of their oxygen-carrying capacity. Without an adequate oxygen supply to meet the requirements of working muscle, the equine athlete cannot meet the demands of competition. The packed cell volume (PCV) and red blood cell count (RBC) indicate the oxygen-carrying capacity of the blood and have been found to increase with training. However, the effect of the release of splenic reserves of red blood cells on RBC and PCV must be remembered. Age, sex and breed will also cause variation. Rate of Turnover of Red Blood Cells Another important effect of training on the blood is an increase in the rate of turnover of red cells. Cells have a limited lifespan, usually 4 to 5 months. However, as a horse works harder the lifespan of the red cells decreases. Cells travel hundreds of kilometres through the blood vessels and eventually a combination of wear against the walls of the blood vessels and squeezing to pass through the tiny capillaries literally wears the cells out. A working horse pumps the blood through the body more quickly, and so the process of wearing out takes place more quickly too. Younger red cells have a greater ability to carry oxygen, so a fit horse with a younger average population of red cells has a greater oxygen-carrying capacity. Blood Testing The vet can collect blood samples from a horse, have them tested and have the results ready in a couple of days. This makes blood-testing an invaluable tool in helping the vet confirm a diagnosis of illness or assess well-being and fitness to compete. For a blood test to be of any use in determining deviations from the normal, i.e. illness, the normal for that horse must be known. Blood tests can only be of maximum use if taken regularly as part of the horse's training programme. Blood Collection The skin, usually over the jugular vein, is swabbed with surgical spirit and a needle is inserted into the vein (Fig. 5.14); 2 to 3 ml of blood is

< previous page

page_58

next page >

< previous page

page_59

next page > Page 59

Fig. 5.14 Blood sample collection. removed and mixed immediately with an anticoagulant to prevent clotting. A further 5 to 7 ml is taken and placed in a separate tube and allowed to clot for serum examination. Few horses appear to resent this procedure much less so than an injection of antibiotic. It is important that the horse is upset as little as possible, and that it has not been exercised that day as some values change after stress and exercise. The sample should reach the laboratory within 24 hours of collection because blood deteriorates if kept too long. Blood Analysis The unclotted blood is placed in special microscope slides with counting chambers and the total red cells are counted by sophisticated electronic equipment. The haemoglobin content of the blood is estimated. Unclotted blood is then spun at high speed (centrifuged) so that the cells all pack in one end of a parallel-sided tube. By measuring the length of cells in the tube, the percentage PCV is calculated. This test indicates that a horse is dehydrated if there is a larger than normal PCV. Along with red cell count and haemoglobin concentration, PCV can be used to calculate the mean corpuscular haemoglobin

< previous page

page_59

next page >

< previous page

page_60

next page > Page 60

concentration (MCHC). These tests can indicate anaemia due to deficiencies of iron, folate or vitamin B12. A white cell count is also carried out. Any deviation from the normal numbers of white cells is usually because a greater demand is being made upon them, e.g. increased neutrophil numbers indicate bacterial infection and/or inflammation. Lymphocytes produce antibodies to specific pathogens; those that react to viruses are different and can be seen in a blood film, often before the illness is detectable. Eosinophils multiply in allergies (an intolerance to foreign protein); eosinophil numbers also increase if the horse is suffering from a worm burden. Monocytes can increase as part of an immune reaction, or when bacterial infection is present, or if there is an internal parasite infection. White cells are counted as a whole and the different types are also counted. Serum Examination When blood is allowed to clot, the remaining fluid is called serum. When anti-clotting agents are added and the cells removed, the remaining fluid is called plasma. Plasma consists of serum plus the agents involved in clotting. Serum is examined for proteins and enzymes (biological catalysts that enable metabolic processes to take place), a process called serum biochemistry. Serum proteins are of two main types: albumin many globulins. Albumin is made in the liver when the diet is adequate, and globulins are produced by the immune system and are known as 'antibodies' to disease. As the animal ages, more diseases are encountered; antibodies increase and so globulins and the total blood protein increases. Younger animals naturally have lower total protein in the blood, and this cannot be increased by feeding more protein. Low albumin usually indicates that the diet is poor or that albumin is being lost, as during worm infestation. Correct functioning of organs of the body can be tested. For example, liver function is checked by protein estimations and serum enzyme tests; kidney function is tested by measuring serum protein and serum urea. Muscle is rich in an enzyme called creatine phosphokinase (CPK), and damage to muscle causes an increase in CPK levels. Testing for this enzyme helps in diagnosis and treatment of azoturia.

< previous page

page_60

next page >

< previous page

page_61

next page > Page 61

With specialised equipment, the blood can also be tested for a full range of minerals. It may be wise to have a horse's blood tested for selenium if you live in a selenium-deficient area. It must be remembered that each horse is different what is normal for one horse may be unusual for another. Ideally, not only should the normal for each horse be known but the results of the test should be compared to a table of the laboratory's normal ranges of results (Table 5.1). Table 5.1 Normal range of blood test values. Haematology Red cell count

8.511 million/mm3

Haemoglobin concentration

1317 g/100ml

Packed cell volume

3444%

Mean corpuscular volume

3845 femtolitre

Mean corpuscular haemoglobin concentration

3239 g/100 ml

White cells

600012000/mm3

Neutrophils

20008000/mm3

Lymphocytes

15004000/mm3

Eosinophils

100600/mm3

Monocytes

100600/mm3

Basophils

2050/mm3

Biochemistry Serum proteins total albumin globulins

5575 g/l 2541 g/l 2541 g/l 1:1 ratio

Urea

2045 mg/100 ml

CPK

2080 iu/la

aiu = International unit. Interpretation of the Blood Test This is the job of the veterinary surgeon (see fig. 5.15), requiring experience and professional expertise. However, some signs can be looked for:

< previous page

page_61

next page >

< previous page

page_62

next page > Page 62

Fig. 5.15 Blood test results.

< previous page

page_62

next page >

< previous page

page_63

next page > Page 63

(1) Infection (a) Bacterial increased total white cell count an increased percentage of neutrophils (b) Viral decreased total white cell count more lymphocytes presence of virus lymphocytes (2) Anaemia reduced red cell count low haemoglobin concentration Anaemia is usually found in the following circumstances: poor nutrition worm burden deficiencies of iron, vitamin B12, folic acid internal bleeding, e.g. from gastric ulcers or lungs. (3) Dehydration This is a lack of body fluid caused by fluid loss being greater than fluid intake (e.g. after illness, exertion, water deprivation), and is shown by the PCV. (4) Muscle damage May result from injury, exertion (especially during dehydration or illness) or azoturia, and is shown by high CPK levels.

< previous page

page_63

next page >

< previous page

page_64

next page > Page 64

6 Bone and Hoof Structure Bone. Structure and Function Bone is the hard substance making up the body's skeleton, on which the soft tissues hang. Bone is composed partly of living fibrous tissue and partly of non-living calcium and phosphorus salts. The living tissue is called collagen, a fibrous protein also found in tendons and cartilage. The collagen is organised into a matrix encrusted with mineral crystals, mostly calcium phosphate. The proportion of living to non-living (mineral) material in bone varies according to the age of the horse. Young horses have soft bones consisting of 60% fibrous tissue, whereas adult animals have more brittle bones containing only 35% fibrous tissue. Although bone appears to be hard, dense, inelastic and almost lifeless, its structure is constantly changing the entire calcium content of the skeleton is replaced every 200 days. Bone serves as a mineral reservoir and is being constantly replenished or depleted. No tissue in the body is capable of as much growth and as much absorption as bone. Bone is of two types: dense and spongy. Dense bone is found in the shafts of the long bones of the limbs. Under the microscope, dense bone has a tube-like form with a central cavity containing fatty yellow marrow. The outer surface is covered by the bone membrane, or periosteum. Spongy bone is round in the short bones and at the ends of long bones. It has a more open framework than dense bone and contains red bone marrow. Red blood cell synthesis takes place in red bone marrow. All bone is penetrated by a series of very fine canals in which blood vessels, nerves and lymph vessels lie. These bring the stimuli and nutrition necessary for growth, maintenance and repair of bone. Bone has many functions in the body other than providing support and rigidity. Bones are the levers that give muscles something to work

< previous page

page_64

next page >

< previous page

page_65

next page > Page 65

against; they protect internal organs and act as stores of calcium and other minerals. The mechanical function (support, leverage or protection) determines the shape of each bone, leading to bones being classified by shape. (1) Long bones. These are main supporting columns and levers, e.g. the cannon bone, being cylindrical shafts with enlarged ends called epiphyses. (2) Flat bones. These act as protectors, e.g. the skull which protects the brain. (3) Short bones. These act as shock absorbers, e.g. the small bones of the knee and hock joints. (4) Irregular bones. These are bones with a special role to play, e.g. the vertebrae. Regardless of their shape, the composition of these bones is similar. A cross-section of a long bone (Fig. 6.1) shows an outer layer of dense material called 'compact bone' which is thickest where stress is the greatest, nearest to the outer surface of the cylinder. There is an inner layer of spongy bone which is interspersed with marrow. Marrow is involved with the production of blood cells. Long bones have spongy bone at either end while the interior of the shaft is hollow and filled with marrow.

Fig. 6.1 A cross-section through a long bone. Bones are surrounded by the periosteum, which acts as an attachment point for the ligaments and tendons. The periosteum is lined with cells called osteoblasts, which produce new bone. The periosteum also brings nutrients to the bone via blood vessels and nerves that enter the bone through a series of canals. The joint surfaces of the bones have a cap of shiny resilient cartilage

< previous page

page_65

next page >

< previous page

page_66

next page > Page 66

Fig. 6.2 The structure of a joint. (Fig. 6.2), which provides a smooth articulating surface and lubrication in the form of synovial fluid. Formation and Growth In the unborn foal, bone begins as cartilage. Bone-forming cells (osteoblasts) invade the cartilage and begin to secrete the matrix; minerals are deposited on the matrix and it calcifies into bone. By the time the foal is born, calcification is complete in most bones (Fig. 6.3). Growth of Long Bones Bones have to increase both in length and diameter. Increase in length takes place at two narrow bands of cartilage, one near each end of the

< previous page

page_66

next page >

< previous page

page_67

next page > Page 67

Fig. 6.3 The growth and development of a long bone.

< previous page

page_67

next page >

< previous page

page_68

next page > Page 68

bone. These bands are called the epiphyseal 'growth' plates (Fig. 6.4). Cartilage grows on the side of the growth plate nearest the end of the bone, while the shaft side of the growth plate is invaded by osteoblasts which turn the cartilage into bone. Gradually the osteoblasts gain on the cartilage, and when the bone has reached its proper size the plate closes and becomes bone. Different bones stop growing at different times; for example, growth plates of the cannon bone close at 9 to 12 months and those of the tibia at 3 1/2 years.

Fig. 6.4 The activity of the epiphyseal plate. Bone increases in diameter through the action of the osteoblasts lining the periosteum. These cells lay down new material in layers over the old bone, giving a ring-like effect similar to the rings of a tree trunk. Simultaneously, old bone is destroyed by osteoclasts so that the marrow-filled cavity grows and the shaft wall is only slightly thicker. Osteoclasts break up dead and damaged bone and reduce the size of any callus or thickening where a mend occurs.

< previous page

page_68

next page >

< previous page

page_69

next page > Page 69

Adaptation of Bone to Stress After growth stops, bone undergoes a process called 'remodelling'. This involves a balance between the formation of new bone and the reabsorption of old bone, and has two main functions: it allows the use of mineral stores and enables adaptation to stress. Remodelling starts when the foal is about 3 months old, when the newly formed bone begins to rearrange itself into 'Haversian systems'. These systems consist of a series of vertically aligned tubules through which the blood vessels travel. Remodelling is usually complete by the time the horse is 6 years old. If the Haversian systems are formed too quickly with too little mineral content, the bone becomes porous, and porous bone is not as strong as dense bone. This will happen if the calcium supply in the diet is not adequate, so a correctly balanced diet is essential for the development and maintenance of a healthy skeleton. The Effect of Exercise On Bone Although bone appears lifeless, it is extremely responsive to environmental changes. Changes in pressure, blood supply and nutrition can all bring about changes in bone structure. Bone can decrease in size (atrophy), increase in size (hypertrophy), repair breaks and rearrange its internal structure to resist stress and strain. Bone is able to reshape itself to sustain a maximum of stress with a minimum of bone tissue. The effect of exercise on bone depends on several factors including age, duration of training, intensity of training, and injuries. Atrophy of bone occurs where constant and excessive pressure is applied, or where periods of pressure exceed periods of release. Proliferation or hypertrophy of bone occurs in response to concussion or intermittent pressure. Whether bone atrophies or proliferates under pressure is largely dependent on the degree and duration of the pressure and on the maturity of the bone. Pressure on growing bone will slow down and may even stop growth. Mature bone responds to pressure by excess growth or rearrangement of its structure. These changes often exhibit themselves as problems such as splints, ringbone and other bone diseases, and will be discussed later. Short bones such as the bones of the knee joint are not as resistant to compression and pressure as are long bones such as the cannon bone. Thus short bones tend to develop bony growths or hairline fractures which are painful, restrict movement and often will not heal. The bones of the foot are short bones. The navicular bone is sand-

< previous page

page_69

next page >

< previous page

page_70

next page > Page 70

wiched between the pedal bone and the short pastern bone. Both these bones are very much larger and very much more dense than the navicular bone which is subject to damage from crushing forces sustained during galloping and jumping, contributing towards navicular disease. During exercise bone is subjected to stretching forces (tension). Bone is relatively inelastic a rod of bone can be stretched by about 0.005% of its length before breaking. If stretched to near breaking point, bone will not return completely to its original length. Under stress bone deforms and does not return to its original length an exaggerated example of this is seen in rickets. Bone is also subject to compression, shearing, bending and twisting during movement. A bone will support more weight when the animal is stationary than it can bear under a dynamic or moving load. The leg bones of a horse bear a static or stationary load when the horse is standing still and a dynamic load when the horse is galloping and jumping. Movement causes compression, bending and shearing stresses. When a horse pivots with one foot in contact with the ground, twisting stresses are added to the bone. Muscles and tendons act like 'guy wires' to reduce stresses of all types on the bone. To do this effectively, the muscles and tendons must themselves be capable of withstanding the stresses: they must be fit. Bone responds to the stress created by exercise by remodelling and laying down more bone so that the mass or weight of the skeleton is greater. Conversely, if bone is not subjected to stress it is reabsorbed and the mass of the skeleton decreases. Every time a horse is ridden the bone is stressed and the skeleton undergoes changes. This means that when we condition a horse's muscles we are also conditioning the skeleton. The skeleton is the foundation of the performance horse and it is important to be aware of the effect that work is going to have on the horse's bones. Bone is a rigid structure and cannot be moulded. The only way that it can change shape is by adding more bone to its surface or by taking bone away. Bone can only repair damage or change its internal structure by the osteoclasts 'drilling' a hole towards the damaged area and the osteoblasts filling in the hole behind them. It would seem that during repair bone actually goes through a weak stage, because the first stage of repair is to remove bone, thus weakening it, before the osteoblasts can go in and repair the damage. If bone is damaged during training and training continues, a vicious circle is set up: less bone, more damage, more reabsorption, less bone, etc. This can eventually lead to stress fracture (Fig. 6.5) the bone breaks due to repetition of

< previous page

page_70

next page >

< previous page

page_71

next page > Page 71

Fig. 6.5 How a stress fracture can occur. stress in much the same way that a piece of wire breaks after being bent repeatedly. In a horse these stress fractures can be seen as 'sore shins', a consequence of training young horses on hard ground. Controlled amounts of stress will benefit the bone by stimulating the remodelling process, resulting in more dense, stronger bone. A training programme should contain periods of brisk trotting, and exercise should be as diverse as possible, certainly including all types of stress to which the bone will be subject during competition. It is beneficial for exercise to be vigorous, thus inducing high levels of strain, but these levels should not continue for long periods. It takes about 3 months of work before remodelling has significant effects, but the process goes on for many months and the effect will vary between individuals. One study of professional tennis players found that on the serving side of their body they had an average of about 35% more bone than on the non-serving side, some having as much as 100% more.

< previous page

page_71

next page >

< previous page

page_72

next page > Page 72

The stress a horse's bones receive has been divided into three types: (1) The elastic zone. The normal elastic properties of the bone allow it to absorb the impact of 9 to 13.5 kilonewtons (kN) (2000 to 3000 lbf) each time the forelegs hit the ground (an easy canter) with no change to its structure. (2) The fatigue zone. The bone does not return to its original state after each stride, and slow deformation occurs. The fatigue zone is reached during fast galloping when each foreleg experiences about 40 kN (9000 lbf) force as it lands. When the horse rests the bone repairs itself and is stronger. However, if there is insufficient time for healing before the next gallop, the bone may become permanently damaged up to 4 weeks may be necessary. If the skeletal system is to be made significantly stronger, the horse must undergo work in the fatigue zone. (3) The overload zone. The bone has no elasticity left in it; it undergoes severe deformation, and snaps. This occurs at a force of about 55 to 80 kN (12,000 to 18,000 lbf), which can happen if the bone is loaded unevenly for example, round a turn where the entire force may fall on one side of the cannon bone (see Fig. 6.5). The changes in density of bone can be measured by the velocity of ultrasound waves sent through the bone, a high velocity indicating strong, dense bone. This technique has been used extensively in the U.S.A. to demonstrate the effect of exercise on bone. Although it is not definitely known how stress stimulates osteoblasts to produce more bone, the signal is thought to be electrical in origin. Mild electric currents induced by magnetic fields have been shown to speed the healing of broken bones in humans. This idea has been introduced into equine therapy to aid healing of bone-related conditions. Reducing or ceasing training will result in bone remodelling, with production of weaker bone. When putting horses back into training after a rest, they should be returned to an earlier part of the training cycle, i.e. shorter distances, slower speeds and less stress. This will allow the bone to strengthen again. Corticosteroids in excess, whether due to administration or the horse's own response to severe stress, will also result in a weakening of bone or lack of development. It can be seen, then, that bone can be conditioned just like the other body systems, and it must be stressed in order to sustain the loads put upon it by the demands of performance.

< previous page

page_72

next page >

< previous page

page_73

next page > Page 73

Diseases of Bone Bones are deeply seated within other tissues and are not richly supplied with blood, which means that bone disease is often overlooked. Diseases of bones fall into five main categories: periostitis osteitis disorders of the growth plates (epiphysitis) infection fracture. Periostitis This is inflammation of the surface of the bone and its covering surface (periosteum). It is most usually caused by sprain, blow or infection, and the symptoms are pain, swelling and heat over the affected area. Examples of conditions caused by periostitis are ringbones, osselets, sore shins and spavins. Ringbones involve the growth of new bone (exostosis) on the pedal bone, short pastern or long pastern bone. The condition is caused by trauma (e.g. a blow or tread), underlying bone disease, nutritional deficiency or infection. Ringbones are classed as high or low depending on where they are sited. Osselets involve growth of new bone on the front of the fetlock. The condition is caused by concussion leading to inflammation of the periosteum of the fetlock joint. Sore shins arise due to the lining of the cannon bone being inflamed, caused by galloping on hard ground. The periosteum becomes detached and new bone is formed. Spavin is a condition of the hock joint. Bone spavins are caused by periostitis or osteitis of the upper end of the cannon bone and some of the small bones of the hock, causing lameness. Osteitis This involves inflammation of the bone substance itself the most common complaint is pedal osteitis, where the pedal bone is inflamed causing pain and lameness. Epiphysitis. Epiphysitis occurs when the growth plate becomes inflamed. This may be caused by infection, trauma or an imbalanced diet (e.g. excess

< previous page

page_73

next page >

< previous page

page_74

next page > Page 74

protein or an incorrect mineral balance). It is most common during periods of rapid growth for example, in the lower end of the radius (the bone immediately above the knee) at 12 to 24 months. The symptoms are pain, swelling and lameness. Infection This can be very serious, and may require surgical intervention. Fractures Fractures can be classified according to the age of the animal and the type and site of the break. Fractures of small bones (e.g. splint) may not be serious, while breaking a large weight-bearing bone can result in the horse having to be destroyed. Splints may arise from fractures of the splint bone resulting in a callus. The cause may be a knock, as when one foreleg strikes another. Prevention Many of the diseases described here arise as a result of concussion or trauma. In other words, they are exerciseinduced injuries and as such they are common in performance horses. Bone is well able to adapt and thus withstand the stress of the horse moving; it is only when the stress becomes excessive or prolonged that these diseases arise. By understanding the processes that cause the stress and the response of the bone to that stress, the rider should be able to avoid placing their horse in a position where the stress becomes excessive. Developing the horse's muscle, bone and tendon by a planned, systematic training programme will help the horse adapt to the demands made on its body and help minimise the risk of these injuries and diseases occurring. Joints Joints have a very important role in equine biomechanics, but work done in this area is sparse. Synovial joints include a number of different structures, i.e. articular cartilage, ligaments, joint capsule, synovial fluid and subchondral bone. Joints withstand high-impact forces as the horse moves at speed. With increasing loads, the load is spread over a larger articular area to reduce stress on the joint. Joints also respond to exercise. Movement and loading are essen-

< previous page

page_74

next page >

< previous page

page_75

next page > Page 75

tial, as both improve the health of cartilage by exchanging nutrients with synovial fluid. Resting horses results in atrophy of cartilage, so horses returning to training should be started at an earlier point of the training programme. Excessive exercise may lead to fibrillation of cartilage and reduced proteoglycan content. Proteoglycans are molecules responsible for cartilage stiffness and compressibility. Very strenuous exercise will therefore lead to degenerative joint disease (DJD). DJD is traumatically induced and is probably the most common joint problem in performance horses. The Hoof The foot of the horse (Fig. 6.6) consists of a horny box which surrounds the pedal bone, the navicular bone, ligaments, tendons, the digital cushion, sensitive laminae, blood vessels and nerves. The horny box is called the hoof and consists of a wall divided into toe (at the front) and quarters (at the side). The sole, bars and frog are underneath. The wall is bent sharply backwards at the heels to form the bars. The hoof wall is manufactured by specialised cells of the skin (corium) and, in effect, is modified skin or nail. The wall is about 25%

Fig. 6.6 The structure of the foot, showing bones and tendons.

< previous page

page_75

next page >

< previous page

page_76

next page > Page 76

water and is protected from evaporation and thus drying by an outer layer called the periople. The middle layer of the wall is dense and hard and contains pigment in dark-coloured feet. The inner layer of the wall is called the laminar layer and forms specialised membranes of laminae which attach the hoof to the pedal bone (Fig. 6.7). There are hundreds of tiny primary laminae, each of which has about 200 secondary laminae. These interdigitate or 'dovetail' with sensitive laminae which cover the outside of the pedal bone. This means that, although each small pedal bone supports about a quarter of the horse's weight, the burden is spread over a very large surface area. If this were not the case, the pedal bone would be pushed through the sole of the foot as in laminitis. On the ground surface, the wall is united to the sole by horn of a lighter colour and softer texture, called the 'white line'. This marks the boundary of the sensitive laminae, and thus shoeing nails must be outside this line. The sole is the ground surface of the hoof, and is concave in shape and bounded by the walls and bars. The frog is a wedge of soft horn between the bars and is the most elastic structure of the foot. Inside the hoof, above and around the frog, covering the heel, is some soft tissue called the digital cushion or plantar cushion. On either side of the pedal bone are two plates of cartilage called the

Fig. 6.7 Horizontal section through the horny wall and laminae of the hoof.

< previous page

page_76

next page >

< previous page

page_77

next page > Page 77

Fig. 6.8 The structure of the foot, showing the digital cushion and lateral cartilage. lateral cartilage (Fig. 6.8). The frog, digital cushion and lateral cartilages act together as an anti-concussion mechanism and an aid to blood circulation in the foot and leg. As the foot strikes the ground and the horse's weight travels over it, the frog is forced into the bars, the heel expands and the forces of concussion are distributed. The digital cushion is compressed against the frog and lateral cartilages and the lateral cartilages move outwards, forcing blood out of the veins and capillaries trapped between the cartilages and the wall. This has two effects: firstly, the blood is forced out of the foot up the leg, and secondly, the blood confined within the hoof wall has a hydraulic shock-absorbing effect. If the horse is confined to its box, this forced return system of blood is inactive, resulting in a poor blood flow and filled legs. Nails placed too far back in the quarters of the foot inhibit the elasticity of the heels and their ability to expand, and thus affect blood flow within the foot. Frog contact is also very important in ensuring shock-absorption and correct blood flow in the foot. Growth of the hoof takes place at the coronet, at a rate of approximately 0.6 cm (0.25 in) a month, taking 9 months to grow from

< previous page

page_77

next page >

< previous page

page_78

next page > Page 78

coronary band to toe. Growth of healthy hoof reflects the state of health and the plane of nutrition of the horse. Heart and lung development are vital to the well-being of the feet, because the structures of the foot require a large volume of blood. This blood is needed for nourishment of tissue, maintenance of warmth and dissipation of heat. Many diseases of the foot may be partly attributable to poor circulation for example, navicular disease and sidebones. Exercise will have an effect on hoof growth. As the horse works, its heart rate increases and blood is pumped more rapidly round the body. The blood supply to the foot and coronet is increased, bringing with it a supply of nutrients for growth; thus hoof growth increases. Simultaneously, the plane of nutrition of a working horse improves as feed is increased, supplying the nutrients necessary for increased hoof growth. By looking at the growth rings on the hooves of a hunter it is possible to show quite clearly when the horse was brought into work and when turned away.

< previous page

page_78

next page >

< previous page

page_79

next page > Page 79

7 The Dental System Teeth are the beginning of the digestive system of the horse and they have a very important role to play. The horse has two sets of teeth during its life: (1) Temporary or milk teeth, smaller and whiter than permanent teeth. (2) Permanent teeth, larger and yellower adult teeth.

Fig. 7.1 The incisor tooth.

< previous page

page_79

next page >

< previous page

page_80

next page > Page 80

The horse has only three types of teeth: incisors or biting teeth in the front of the mouth (Fig. 7.1) molars or grinding teeth lining either side of the jaw bone the cheek teeth (Fig. 7.2) tushes or canine teeth.

Fig. 7.2 The molar teeth. There are six incisors in each jaw: two corners, two laterals and two central incisors. These teeth are used to age horses. There are twelve molars to each jaw, six each side. A horse has an adult mouth of permanent teeth as a fiveyear-old. Adult male horses have two tushes in each jaw, situated between the incisors and the molars, but mares rarely have tushes thus mares have a total of 36 teeth and geldings and stallions 40 teeth.

< previous page

page_80

next page >

< previous page

page_81

next page > Page 81

Occasionally 'wolf-teeth' may erupt in the upper jaw. These are vestigial pre-molar teeth which may cause problems, interfering with the bit action and causing pain. It is probably best to have them removed by the horse dentist or vet. The horse's teeth are designed to eat grass: the incisors can nibble short grass close to the roots, while the ridged surface of the molars grind the tough fibrous grass before swallowing. The horse's head is shaped so that the upper jaw is wider than the lower one in other words, the molars overlap each other at the sides. Horses' teeth grow continually upwards out of the gum and are continually worn away by grinding fibrous food. As the jaw moves from side to side during chewing the molars grind against each other, but the lower ones do not reach the outer edge of the upper molars and the upper molars never reach the inner edges of the lower molars. Eventually these edges become long and sharp and can cut the cheeks and tongue, making eating and carrying a bit painful. Quidding, which is the dropping of half-chewed food out of the mouth, is a sign of sharp molar teeth. The vet or horse dentist can file the edges of the molar teeth, levelling them with the rest of the molar teeth, a process called rasping or floating. To avoid problems, a horse's teeth should be checked twice a year and rasped if necessary.

< previous page

page_81

next page >

< previous page

page_82

next page > Page 82

Summary of Part II The Effects of Exercise On the Body As the horse begins to work, there is an increase in muscular activity. Muscles need energy to contract; initially, this energy is supplied by the breakdown of fuels stored within the muscle cells. When these stores run out, fuels are supplied from other parts of the body, e.g. the liver, and brought to the muscle cells in the bloodstream in the form of glucose and free fatty acids. Releasing energy for muscle contraction from these fuels with optimum efficiency requires oxygen. Oxygen is supplied by the lungs via the red blood cells which carry it in chemical combination with haemoglobin. A toxic waste product, carbon dioxide, results from this fuel breakdown, and it must be removed from the cells if the muscles are to continue working. The carbon dioxide is removed, attached to haemoglobin, by the bloodstream and expelled from the lungs. This means that not only does the bloodstream supply oxygen and other nutrients, but it also removes waste products. The harder the horse works, the more rapidly its muscles contract and the more oxygen is needed. The heart, which is responsible for pumping blood round the body, must increase its rate and power of pumping as exercise increases. The rate and depth of breathing must increase so that more oxygen is drawn into the body. Together, the increased heart and respiration rates ensure an increased supply of oxygen to the muscle cells. As exercise increases, the adrenal glands release the hormone adrenalin. This promotes a fight-or-flight reaction in the horse, increasing both breathing and heart rates, and mobilising body fuels from their storage depots. The spleen also contracts, thus releasing a large volume of blood into the circulation and increasing the oxygen-carrying capacity of the body, aiding muscle contraction. During very strenuous exercise, when the muscles are working (i.e. contracting) at maximum capacity, the oxygen demands of these

< previous page

page_82

next page >

< previous page

page_83

next page > Page 83

muscles exceed the amount of oxygen that can be supplied by the blood. The energy for contraction has to be supplied from fuel supplies in the absence of oxygen, or anaerobically. This anaerobic respiration is not as efficient in producing energy as aerobic respiration, and can be described as high short-term power at the expense of limited fuel sources. A poisonous waste product, lactic acid, is also produced, and is considered to be a major contributor to muscle fatigue. Lactic acid in the presence of oxygen is either eliminated as carbon dioxide and water, or converted back to glycogen in the liver. Excessively high levels of lactic acid are associated with muscle cramps and muscle damage. At the end of exercise, a horse blows until all the lactic acid is removed from the blood. At slower levels of exercise, oxygen demand equals oxygen supply and lactic acid does not accumulate.

< previous page

page_83

next page >

< previous page

page_85

next page > Page 85

PART III THE PERFORMANCE HORSE HEALTH PROBLEMS.

< previous page

page_85

next page >

< previous page

page_87

next page > Page 87

8 Lameness Tendon Injury Tendon Structure Figures 8.1 and 8.2 show the anatomy of the horse's lower limb. Tendons consist of bundles of individual collagen fibres on which the strength of the tendon depends. These collagen fibres are longitudinally orientated and interspersed with fibroblast cells. The fibroblasts produce a material which, under certain conditions, joins together to produce long collagen fibres. The conditions needed are correct salinity, acidity and oxygen supply. Collagen production in the tendon is continuous, which means that tendons are dynamic structures like bones. Normally, the collagen in the tendons of the lower limb is entirely renewed in 6 months. Special enzymes trim off excess collagen and also dispose of damaged and old fibres. This constant formation of collagen means that it is very important that there is satisfactory blood flow through tendon tissue, bringing oxygen and nutrients. However, the blood system through the tendon is very modest and easily upset, even by very slight strains and sprains, reducing the oxygen supply and leading to degenerative changes. Blood Supply Each tendon is covered by a thin layer of connective tissue, which continues into the fibres and separates bundles of fibres; this tissue also carries blood, lymph and nerves. The whole tendon is usually enclosed in the tendon sheath. There are 'cold regions' in the horse's lower limb where the blood supply is less efficient. These are: check ligament middle of the superficial digital flexor tendon around the fetlock joint

< previous page

page_87

next page >

< previous page

page_88

next page > Page 88

Fig. 8.1 Bones of the lower limb. It is in these regions that degenerative changes commonly occur; they are seen as slight heat and swelling. Any heat in the lower limb should be taken seriously, as ignoring these early warning signs may lead to more severe problems later on. Collagen Fibre Structure Collagen is the most abundant protein found in the mammal's body,

< previous page

page_88

next page >

< previous page

page_89

next page > Page 89

Fig. 8.2 Ligaments and tendons of the lower limb. being present in skin, bone, tendons and ligaments. There are four types of collagen: Type I: bone and tendon Type II: cartilage Type III: foetal membrane, cardiovascular system Type IV: basement membrane Type I collagen is the strongest form, the strength arising from its 'crimped' structure. Collagen itself is inelastic, but if put under strain the crimped structure can be pulled straight, allowing the fibre to increase its length by 4% and thus absorbing strain. As the collagen fibres age, or as they are used, the amount of crimp decreases; the tendons become less efficient and are replaced. Collagen fibres are replaced in response to the demands made upon them, so in the working horse fibres are replaced quickly; the average age of the

< previous page

page_89

next page >

< previous page

page_90

next page > Page 90

collagen fibres is younger and consequently the amount of crimp is greater, and the amount of stress and strain that can be tolerated greater. In the idle horse the turnover of collagen decreases and crimp is lost and not replaced, so if such a horse is brought into work suddenly the tendons are less likely to withstand the workload. Getting Tendons Fit Traditional fittening programmes involve weeks of walking work to 'harden the horse's legs' and while the terminology may be confusing, there are sound practical and physiological reasons for beginning the programme with gradually increasing amounts of walking. The unfit horse has tendons containing elderly collagen fibres, lacking in crimp and thus unable to stand faster work without the risk of damage. Walking work stimulates the blood flow to the tendons and encourages increased turnover of collagen fibres, resulting in stronger, more efficient tendons by the time faster paces are introduced into the training programme. Injury The horse appears to be particularly susceptible to tendon problems of the lower limb, and tendon injuries are a major cause of lameness in all performance horses. Tendon injury falls into two broad categories: mechanical degenerative. Mechanical damage is the result of injury for example, a horse striking itself or being struck by a sharp or blunt object. Wounds due to glass or wire can occur, most commonly below or on the fetlock. The nature of the wound may vary from a bruised to a cut or severed tendon. When the tendon is bruised, there is haematoma; the fibres in the tendon become separated by bleeding within the tendon, causing painful swelling. This haematoma will eventually be reabsorbed and the swelling will subside. However, there may be scarring within the tendon and adhesions may form. Adhesions are areas where healing tissue becomes 'stuck' to overlying and underlying tissue, thus limiting the freedom of movement of the part. Mechanical damage can be particularly serious if the wound becomes infected. Recovery is slow, and there may be extensive scarring and adhesions. The superficially situated tendons, the superficial digital flexor tendon and the extensor

< previous page

page_90

next page >

< previous page

page_91

next page > Page 91

tendons (see Fig. 8.2), are the most susceptible to mechanical damage. Sudden strains or sprains may occur after a specific incident, such as putting a foot in a hole, overtiring an animal or running into a very wet piece of ground. Degenerative damage is more complex, and is essentially provoked by a lack of oxygen in the tendon leading to partial or complete tendon rupture. The onset of 'a leg' is more insidious, arising from repeated stress (Fig. 8.3).

Fig. 8.3 Tendon damage. Causes of Tendon Injury (1) Muscle fatigue. When the muscles are tired, muscle co-ordination can become upset; the muscles to which the tendon is attached may become inelastic, so that all the elasticity falls on the tendon, stretching it beyond its safety margin. Muscle fatigue will occur more rapidly in heavy and uneven going, and if the horse is jumping. (2) Fitness. Unfit horses with little muscular strength become tired and unco-ordinated more easily. (3) Foot care. Bad or irregular shoeing can lead to the horse having toes that are too long and heels too low, causing overextension of the fetlock joint and strain on the flexor tendons. (4) Conformation. Horses that are too heavy for their limbs, have long cannon bones, long pasterns, crooked limbs, etc. are all more at risk due to the extra strain being placed on the tendons.

< previous page

page_91

next page >

< previous page

page_92

next page > Page 92

Signs of Tendon Injury. Mechanical Injury The signs of mechanical injury are usually dramatic, but vary according to which tendon is damaged and the extent of the injury. The horse will be lame and, even though the exposed or frayed tendon may be seen within the wound, there will be little bleeding: veterinary attention will be necessary. These wounds always cause great concern, but generally mechanical injury is less of a healing problem than tendon damage resulting from degenerative change. Degenerative Change Degenerative change can be an insidious process, although strains and sprains can happen quickly, e.g. if a horse gallops into very soft, boggy ground. Several hours after exercise the tendon will show signs of inflammation, i.e. heat, swelling and soreness over the tendon. One or both forelegs may be affected, and either or both tendons may be involved. In acute sprains, the horse may pull up lame or go lame shortly after the injury. The horse may stand with the heel held up to ease pressure on the flexor tendon area. The knee will be cocked forward at rest and the horse will not allow the fetlock to drop when moving to avoid painful pressure. The tendon may have a 'bowed' appearance (Fig. 8.4). Effects of Tendon Injury The initial tendon injury is due to tearing of some of the tendon fibres and haemorrhage (bleeding) within the tendon leading to inflamma-

Fig. 8.4 Different areas of tendon strain.

< previous page

page_92

next page >

< previous page

page_93

next page > Page 93

tion. The tendon is surrounded by firm tunnels and encircling ligaments (annular ligaments), and it is these that cause a great deal of the damage in a bowed tendon. The ligaments cause pressure and damage when the injured tendon swells, leading to tissue death which may involve the tendon sheath. Dead tissue is replaced by scar tissue, which is inelastic and laid down in a haphazard fashion. Thus it is the inflammation that causes much of the damage which leads to effects such as the tendon sheath telescoping around the deep and superficial flexor tendons, and adhesions being formed between the tendons and tendon sheath. This means that the tendon loses its ability to stretch and is much more susceptible to re-tearing. Healing of Tendons Healing is preceded by an inflammatory process involving heat, swelling and pain. The tendon fibres are damaged and the body's reaction is to cause cells to move into the damaged area. Here, these cells and others released from the damaged blood vessels dissolve away the damaged fibres, blood clots and debris associated with the wound. The damaged fibres are replaced with granulation tissue, which is a repair tissue with a large number of cells rather than fibres, leading to the tendon being permanently thickened. Gradually, scar tissue containing collagen fibres is laid down. However, these collagen fibres are laid down in a haphazard fashion, not longitudinally in the direction of pull along the tendon, reducing the strength of the tendon. In time these fibres realign themselves so that after 6 months the tendon looks more like normal. Also, the new collagen laid down is Type III collagen, not Type I collagen; Type III collagen lacks crimp and is a weaker, immature form less able to withstand stress. Thus apparently 'healed' tendons will have a greater susceptibility to further injury. Type III collagen is eventually replaced by the original Type I collagen, but this may not occur until more than 12 months after the injury. It is important that the new collagen fibres align themselves longitudinally, rather than at random, to give the tendon strength. This longitudinal arrangement depends on mild tension being applied to the healing tendon. This is applied by short periods of walking in-hand once the initial heat and pain have subsided. Gentle manual flexion and extension of the affected leg for 10 minutes, three times daily will also help. Aggressive therapy may be detrimental, so great care should be taken. Exercise also helps minimise adhesions between the collagen fibres and the tendon sheath.

< previous page

page_93

next page >

< previous page

page_94

next page > Page 94

Slight tendon injuries may need only 1 month to repair, but more severe injuries will need at least 10 months, and preferably 1 year to heal completely. It is inappropriate to return horses to work too soon as further injury will result. Veterinary advice should be followed. Treating Tendon Injury The first step in treating an injured tendon is to control the inflammatory reaction. This will reduce the amount of scar tissue that is formed in the tendon. Once the pain and swelling are reduced, various treatments can be given including, rest, firing, tendon-splitting and carbon fibre implants. Prompt attention can mean the difference between returning to work or retiring after a strained tendon. Pressure bandages, hot and cold compresses and ultrasound physiotherapy can be used. Pressure bandaging is not primarily for support but to cut down the inflammation in the tendon area. Anti-inflammatory drugs can be given, and a plaster cast may be applied by the veterinary surgeon. This will prevent further swelling and provide support for the leg, and will stay on for 7 to 10 days. A second cast may be needed for 2 to 3 weeks, depending on the severity of the injury. After the second plaster has been removed, light exercise in hand will help prevent the formation of scar tissue adhesions in the tendon before the horse is turned away for 9 to 12 months. Controlling the Inflammatory Reaction Inflammation is part of the healing process, but if the leg is excessively swollen more harm than good may be done, and healing may be delayed. Cold water treatments (e.g. cold bandages, hosing (Fig. 8.5), freeze packs) decrease swelling and pain temporarily, and are followed immediately by support bandages to stop excess flow of blood back to the leg. Bandages must be carefully applied to wet legs as they may shrink, and both front legs should be bandaged as the sound leg will be taking most of the weight and so needs support. Heat therapy (e.g. poultices, ultrasound, faradic, magnetic therapy) increases blood supply to the area helping to dispel swelling. Heat treatments should not be used for 48 hours after the initial injury, when the pain has been minimised by cold treatments. Alternate hot and cold therapy acts as a kind of massage, reducing and then stimulating flow of blood to the injury. Massage (e.g. hand rubbing or mechanical vibration Fig. 8.6) will

< previous page

page_94

next page >

< previous page

page_95

next page > Page 95

Fig. 8.5 Cold hosing the lower limb. decrease swelling and help avoid scar-tissue adhesions. Exercise is a cheap form of therapy and the best way of dispelling swelling of the horse's lower limb, provided it is controlled and used with judgement. Once the initial lameness has reduced so that the horse can walk comfortably, 5 minutes' walking in-hand two or three times a day can be very helpful. Further Tendon Treatments Counter-irritation treatments promote the inflammatory reaction by introducing additional irritation. They vary in their severity, the mildest being liniments and the most severe firing. Rubifacient drugs (e.g. liniments, tightners, bracers) are mild applications, accompanied by massage and bandaging, which have a very temporary warming effect and are therefore applied two or three times a day. Blisters are more dramatic in their effect and vary from

< previous page

page_95

next page >

< previous page

page_96

next page > Page 96

Fig. 8.6 Mechanical treatment of a damaged tendon. mild, working blisters causing red, inflamed skin to severe blisters which cause peeling of the skin. Their effect is very superficial, affecting only the skin and immediately underlying tissue, so there is no justification in their use for treating tendons. Firing, the application of hot iron or acid to the horse's legs, has been shown to be at least ineffective and at worst detrimental to tendon healing. The scar tissue produced, far from providing a support to the leg, is both thinner and weaker than normal. The only possible advantage of firing is that it enforces the required rest. The pain it produces then subsides gradually, producing an effect of gradually increasing mobility. Time is the best healer in the case of tendon injury, however, and patient self-discipline on the owner's part is less painful for the horse, less costly and more effective. In the tendon-splitting operation a scalpel is used to make vertical slits through both the damaged tendon and the surrounding healthy area, the aim being to allow the healing elements to penetrate right into the damaged area. However, recent work has shown that tendon-splitting amounts to no more than a sophisticated form of firing and actually delays healing. The relatively new technique of carbon fibre implants is becoming increasingly popular in the treatment of acute tendon injuries,

< previous page

page_96

next page >

< previous page

page_97

next page > Page 97

including ruptured and severed tendons, as well as for the treatment of old, chronic injuries. It involves the use of a plait of carbon fibre filaments which is inserted into the damaged tendon, acting as a scaffolding along which tendon tissue is produced with the fibres running in the direction of the tendon, not at random as in scar tissue. As with all tendon treatments, carbon fibre implants can only be effective if the horse is given adequate rest after the operation at least 9 months and then brought back to work slowly and carefully. Corrective shoeing can help in the treatment of tendon strain. If the suspensory ligament is not involved, the heel can be raised 25 to 40 mm (1 to 1.5 in) for 4 to 6 weeks to take the weight off the bowed tendon. This should be lowered gradually over a period of 6 to 8 weeks. The horse may benefit from being shod with pads or wedges when brought back into work. Treatment of Chronic Tendon Injuries Chronic tendon injuries result from neglected acute tendon inflammation or years of unnoticed slight heat and swelling that gradually builds up into a firm, prominent swelling on the back of the cannon. This swelling is actually scar tissue in the tendon caused by inflammation at the time of injury. Tendon injuries are a common cause of lameness in the competition horse and, while it is accepted that they can occur accidentally and unexpectedly, they are far less likely to occur in a correctly trained, fit horse. A horse should not be expected to do any fast work before its legs and muscles are ready, and tired horses should not be pushed beyond their capabilities. Any signs of heat and swelling in the lower leg should be treated with great care. Once a horse has sustained a tendon injury, it will always need careful management, as the recovered tendon is unlikely to be as strong as one that has never been injured. Although better shoeing and improved training methods may reduce the incidence of tendon damage, and techniques like heat sensitive cameras and force plate studies lead to earlier detection of lameness, damage is certain to occur when horses are pushed to the limits of their performance. Ligament Injury. The suspensory and check ligaments can also suffer strains and rupture. Injuries occurring to the suspensory ligament at its upper attachment to the cannon bone are very serious. The fine fibres of the

< previous page

page_97

next page >

< previous page

page_98

next page > Page 98

ligament fit into tiny holes on the surface of the bone. Once torn loose, the scar tissue formed is too bulky to allow them to return into the holes and instead they adhere to the bone surface; this weak attachment easily loosens. Signs of Suspensory Ligament Injury Lameness and swelling over the suspensory area are signs of injury to the suspensory ligament. If the leg is lifted and the relaxed suspensory palpated, the horse will show signs of pain. The horse will hold the knee and fetlock forward and raise the heel slightly off the ground; the fetlock will not be lowered all the way when the horse is moving. Treatment of Suspensory Ligament Injury Acute strains require complete rest, anti-inflammatory treatment and ultrasound, if available. Chronic strains may be treated with corticosteroids and rest at least 6 months. Blistering and firing have been used in the past with doubtful results. In all types of suspensory ligament injury, a considerable amount of time must be allowed for healing because of the poor blood supply to the ligament. Navicular Disease (Navicular Bursitis) Previously considered incurable, progress is being made in the treatment of navicular disease, a nightmare of all horse-owners. Navicular disease has many causes, and several concurrent factors may together produce signs of the disease. Causes include concussion, hoof and pastern conformation, level of work and regularity, and breed association. Navicular disease is commonly seen in horses over the age of 5 years. The Position of the Navicular Bone The elongated navicular bone is a sesamoid bone lying transversely inside the hoof above the middle of the frog between the short pastern and the pedal bones (Fig. 8.7) and held in position by ligaments. The navicular bone articulates with the short pastern bone, and during movement the weight of the horse presses down and pushes the navicular bone down and back. The back and lower borders of the

< previous page

page_98

next page >

< previous page

page_99

next page > Page 99

Fig. 8.7 The position of the navicular bone. bone are in close contact with the deep digital flexor tendon which rides over the navicular bone before attaching to the pedal bone. In order to allow the tendon to run smoothly over the bone, the back border of the navicular bone is covered in cartilage and a pocket of lubricating joint fluid, the navicular bursa. This area is most under pressure during movement, especially when the foot is on the ground and the weight of the horse is travelling over the leg. Diagnosis of Navicular Disease The onset of navicular disease is usually gradual, and includes signs such as loss of action, shortening of the stride or reluctance to jump. The lameness may be intermittent, the horse coming sound after rest but being lame again if worked. The horse may only be slightly lame, and one or both front feet may be affected. Alternatively, the onset may be sudden after hard work, for example and the horse may be lame in only one leg. Navicular disease seems to improve with low level exercise at first, and is worse after rest. This eventually results in continual lameness. Repetitive concussion from hard work on hard ground seems to be a common causative factor. As the disease progresses, the horse becomes increasingly lame and avoids putting weight on the heels of the foot, so that the toe lands first. This causes the shuffling gait, worn toes and contracted heels characteristic of a horse with navicular disease. Positive diagnosis of navicular disease is often difficult. Initially, the lameness must be identified as being in the foot, and then more specific tests for navicular disease must be carried out. Standing the horse with its toe on a block of wood, e.g. the shaft of a hammer, with its heels unsupported, stretches the flexor tendon which in turn presses on the

< previous page

page_99

next page >

< previous page

page_100

next page > Page 100

navicular bone so that the horse is more lame when trotted up. Pressure to the middle of the frog with hoof testers will increase lameness. The posterior branches of the nerves to the foot can be blocked with local anaesthetic so that pain is removed from the back of the foot. If, after this, the horse goes sound, navicular disease would be strongly suspected. The next step is to X-ray the foot. However, there can be confusion with interpreting X-rays. In a positive diagnosis, one would expect to see widening of the blood vessels supplying the navicular bone; this bone will open out to form an inverted vee-shape as bone is reabsorbed along the line of the blood vessels, giving characteristic 'tree-shaped' erosions of the navicular bone. Some vets say that up to five of these pyramids are normal. Erosion of the Navicular Bone and Cartilage Navicular disease causes erosion of the cartilage on the back border of the navicular bone and spurs of new bone on the side eges; there may also be changes in the flexor tendon running over the navicular bone, including bruising and discolouration, eventually causing adhesion between the tendon and the bone. In extreme cases, there may be fracture of the weakened navicular bone or rupture of the tendon. The erosion of the cartilage and bone can be detected by X-ray as areas of translucency. New bone formation can be seen, and also enlarged openings for the blood vessels supplying the bone as a result of inflammation in the bone. The erosion of bone and cartilage appears to be due to arteriosclerosis of the blood vessels supplying the bone. In other words, the tiny blood vessels are blocked by blood clots so that areas of bone are deprived of the blood supply which brings oxygen and other nutrients. This condition is called ischaemia, and is associated with pain and the death of small areas of bone. The pressure of the flexor tendon wears away these areas of weakened bone, causing the erosion seen on X-ray. The tendon will now be running over an abrasive surface and this causes bruising. New blood vessels also develop in an attempt to supply the bone deprived of blood and nutrients, causing mushroom-shaped canals in the lower border of the bone. However, horses very lame with suspected navicular disease may show no signs on X-ray, while sound horses may have lesions, leading to some confusion in interpreting X-rays. A true diagnosis may be obtained from repeated Xray examination at 4- to 6-month intervals to monitor the progression of the changes in the bone.

< previous page

page_100

next page >

< previous page

page_101

next page > Page 101

Treatment As the cause of navicular disease is not fully understood, treatment is aimed at alleviating the symptoms rather than effecting a cure. The following are possible causes: (1) Continual compression of the navicular bone by the deep digital flexor tendon. (2) Repeated concussion of the navicular bone from below by the frog. (3) There may be a hereditary disposition, possibly related to conformation, e.g. boxy feet, upright pasterns, and an incorrect foot and pastern axis. Boxy feet may, however, be a result of the disease and not the cause. Navicular disease occurs in all types of horses. The farrier may attempt to open out the boxy, navicular foot by grooving the hoof, cutting the heels down and using surgical shoes. An alternative is to allow the heel to grow to relax pressure on the flexor tendon. Bar shoes, pads and wedges will also have this effect. Frequent treatment and balancing of the foot by the farrier should be undertaken. Phenylbutazone ('bute') will only alleviate the symptoms, allowing the horse to work when there are no other alternatives, and as such should not be abused. Isoxsuprine hydrochloride is a relatively new treatment, the effect being to dilate (widen) the blood vessels supplying the navicular bone. A high degree of success has been claimed, particularly if early diagnosis is made and immediate therapy is given. Horses should be encouraged to continue working at a low level, and increases in workload undertaken with great care. If the horse becomes lame again the work should be stopped. A common operation which may be carried out in cases of navicular disease is a neurectomy, which involves cutting part of the nerve supply to the foot so that sensation is lost in the posterior part of the foot. Although generally considered a last resort, this will enable a chronically lame horse to continue work. However, very careful attention must be paid to the foot and shoeing. Often neurectomy will result in continual deterioration of the navicular bone. This may lead to eventual fracture of the bone. A new operation aimed at reducing pressure on the navicular bone is still at the early trials stage.

< previous page

page_101

next page >

< previous page

page_102

next page > Page 102

9 Metabolic Disorders Exertional Rhabdomyolysis/Rhabdomyolysis Syndrome. Muscle myopathy encompasses many types of muscular problem including setfast, Monday morning disease, azoturia, tying-up and paralytic myoglobinuria; it is a surprisingly common problem which can, in some cases, be very severe. Traditionally, it occurs in the fit, stabled horse which has had an enforced rest, e.g. bad weather conditions or the Sunday rest day, while remaining on its full corn ration; it manifests itself on the horse's return to work. Symptoms When the horse is exercised it starts work normally, but after a while begins to feel stiff behind, or after a halt may be unwilling to go forward; it may blow and/or sweat excessively for the type of work being done. If the animal were forced to continue, it would eventually be unable to stand and would go down. It will be sweating profusely, breathing rapidly and showing evidence of acute pain. The muscles of the loins and hindquarters may be swollen and will certainly be tense and painful. Any urine eventually passed will be discoloured, the actual colour varying between amber, port and almost black. It can affect all breeds of horses, all ages and both sexes, although it does appear to be more common in mares, Quarterhorses and endurance horses. If a horse has had a problem once, it is likely-to recur, and such horses must be carefully managed. It is usually exercise-related, although exceptions may occur it can, for example, follow a bout of colic. The condition affects skeletal muscle, usually the back muscles on both sides; however, occasionally forelimbs can be affected. In all cases, the horse will be in pain and the gait will be affected, varying in degree from slight stiffness to an inability to stand.

< previous page

page_102

next page >

< previous page

page_103

next page > Page 103

Treatment Very mild cases showing slight stiffness may wear off with gentle walking exercise. This form is generally referred to as 'tying-up' and many horse-owners do not recognise it as a mild case of azoturia. The majority of cases require complete rest the horse should not even be walked home. A coat should be thrown over its loins to keep them warm, and the animal boxed home. Even the muscular exertion required for travelling may cause further damage. Once in its stable, it is essential to keep the horse warm, particularly over the back region. All concentrate feed should be cut out of the ration and only a minimum of hay and a good vitamin/mineral supplement given. The vet should be called for all but the mildest cases. Treatments may include several of the following: phenylbutazone or corticosteroids to help reduce inflammation in the damaged muscles, a muscle relaxant such as methocarbamol, a sedative e.g. acepromazine to relieve anxiety, and vitamin E with selenium. Recumbent cases may need intravenous fluid and intensive nursing. Fluid therapy will correct the fluid deficit and acidbase balance. The vet may also take a blood sample and test for the presence and concentration of certain muscle enzymes (creatine phosphokinase (CPK), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH)) which can indicate the severity of the attack. Further blood tests will help monitor recovery. CPK is released after stress or damage to muscle. The concentration reaches a maximum in the blood 6 hours after the muscle damage has been sustained and gradually returns to normal, provided there is no further muscle damage. However, CPK levels can normally increase by five times in an unfit horse made to work, so interpretation of readings can be difficult. A few typical clinical cases may not show any increase in CPK levels. The reason for this is not known. The period of rest necessary may vary from a few days to weeks. Exercise must be introduced very gradually, the first day's exercise consisting of 5 minutes' walking in-hand, building up periods by 5 to 10 minutes per day. a sharp look-out should be kept for any recurrences of the symptoms. There may be some scar tissue replacing damaged muscle tissue, and hence some muscle wastage, although this may not be noticeable. Cause The cause of muscle myopathy is not really known, but it is assumed that there are many contributing factors, including exercise of an unfit

< previous page

page_103

next page >

< previous page

page_104

next page > Page 104

horse, irregular exercise and rest on a normal ration. Working a horse beyond its level of fitness may cause the problem. All of these may lead to an upset in carbohydrate or fat metabolism. A deficiency of vitamin E, selenium or electrolytes and an excess of certain types of food, e.g. barley and flaked maize, have also been implicated in the condition. An upset in normal carbohydrate or fat metabolism can cause a build-up of lactic acid in the muscles, which causes muscle damage. The muscle pigment myoglobin is released from the damaged cells and excreted by the kidney via the urine. The myoglobin accounts for the discolouration of the urine of an affected horse. However, the kidney is not designed to cope with excreting myoglobin, and kidney damage can result from severe cases. Precautions Precautions that can be taken to avoid rhabdomyolysis syndrome include the following: (1) Ensure the diet provides adequate forage to maintain potassium and magnesium levels. (2) Provide a salt lick to ensure salt intake is adequate. (3) Do not overfeed cereals. If more energy is required, use high fat compound feeds or add vegetable oil, soya oil or corn oil. If oil is added, horses will require extra vitamin E. (4) Many nutritionists have used electrolytes successfully in the prevention/recurrence of rhabdomyolysis syndrome. Horse-owners should try to ensure electrolytes are given appropriately to horses in work. (5) Horses in the past have been given vitamin E/selenium supplements to prevent further attacks. In some cases this may still be warranted. (6) Feed horses according to work and do not overfeed, particularly cereals. (7) Keep feed ahead of work, i.e. anticipate a rest day by cutting the corn ration. If this is not possible, turn the horse out or walk it out in-hand for 10 minutes. (8) Gradually increase the horse's workload, allowing the muscles to adapt to exercise. (9) Prime the system by thoroughly warming-up the horse before any hard work is done. (10) Ensure that the horse especially one that is fit is kept in regular work.

< previous page

page_104

next page >

< previous page

page_105

next page > Page 105

(11) Some horses of a nervous nature or who become stressed easily may be more prone. Horses should be managed to reduce stress levels. Laminitis Laminitis is commonly known as a problem of fat ponies, particularly in the spring. While such ponies are very much at risk, so also are moderately worked horses who are routinely fed a high proportion of high grain concentrates in their daily ration. Many horses walk a line just this side of a laminitis attack, and it may be responsible for some bouts of sudden, temporary lameness. Symptoms In an acute attack, the feet are usually but not always hot and the horse shows evidence of pain, i.e. sweating and blowing. The stance with the front feet extended, weight taken on the heels and the hind feet crouched underneath to bear the weight is characteristic of laminitis (Fig. 9.1). A useful symptom to look for is a full throbbing pulse in the digital artery. The symptoms may not be so dramatic in a slower-developing case

Fig. 9.1 Typical stance of the laminitic horse.

< previous page

page_105

next page >

< previous page

page_106

next page > Page 106

of laminitis, early signs being withdrawn behaviour, off-feed, reluctance to move and a general air of discomfort. However, in an animal prone to laminitis immediate action should be taken. Causes (1) Digestive. Grain overload, spring grass, cold water in the stomach of a hot horse. (2) Postparturient. Metritis, perhaps due to retention of some afterbirth or a very arduous foaling. (3) Mechanical. Direct damage to the sensitive hoof due to concussion, or excessive foot trimming and rasping, e.g. before height measurement. (4) Stress. Illness, long journeys, or a change in environment. (5) Drugs. Steroids, wormers and antibiotics may cause a reaction in sensitive horses. Laminitis is not a disease of the hoof but of the circulatory system. The causes listed above result in the release of endotoxin (poisons produced in the body). These toxins are vasoactive they cause the tiny capillaries in the hoof to contract, thus denying the sensitive structures of the foot nourishment. Blood continues to travel to and from the foot but it fails to reach toe cells holding the sensitive and insensitive laminae together. The undernourished laminae weaken and die, freeing the pedal bone from some of its essential attachments so that the unopposed pull of the deep flexor tendon causes it to rotate and the sole of the foot drops. Treatment (1) Remove the cause, e.g. the vet may administer mineral oil by stomach tube to flush out the grain from the system, or remove a retained afterbirth. Reduce the diet. (2) Do not exercise or force the horse to walk. The floor should be soft and supportive to the sole, e.g. sand, peat or muck. (3) The vet may administer antihistamine, anti-inflammatory and pain-relieving drugs, e.g. corticosteroids and phenylbutazone, to counteract the changes taking place in the horse's body. (4) Severe cases where the pedal bone has dropped will need remedial foot trimming to realign the bone, and surgical shoeing may also be helpful so that the horse can work normally.

< previous page

page_106

next page >

< previous page

page_107

next page > Page 107

(5) Re-evaluate the ration to reduce starch intake. Seek the advice of a nutritionist or vet for a long-term ration plan. Anaemia. Anaemia is not a disease but a condition of the blood. An anaemic horse has a reduced number of red blood cells and consequently a low level of haemoglobin in the blood. Symptoms The general signs of anaemia are poor coat, pale membranes of eye and gum, muscular weakness, depression, lack of appetite and an increased rate and force of heart beat. The normal red blood cell count is 7 to 8 million per cubic millimetre and the normal haemoglobin levels are 11 to 17 g per 100 ml of blood. Figures indicating anaemia would be 3 to 6 million red blood cells per cubic millimetre and 8 to 11 g haemoglobin per 100 ml of blood. Values such as these reduce the oxygen-carrying capacity of the blood, having an adverse effect on the horse's ability to work. Causes Anaemia can be due to: (1) Loss of blood as a result of rupture of a blood vessel, external or internal bleeding, i.e. haemorrhage. Internal bleeding may result from gastric ulcers or from within a diseased or inflamed respiratory tract. Severe bleeding will follow, for example, rupture of an artery. (2) Increased destruction of red blood cells. (3) Nutritional deficiency. A temporary state of anaemia can be caused by severe or recurring bleeding following serious wounds or episodes of epistaxis (nosebleed). These anaemias are easily reversed if the overall body condition is not lowered by infection or continued blood loss. Bleeding involves the loss of all components of the blood: red and white blood cells and plasma, and transfusions of plasma or whole blood may be required if bleeding is severe. Destruction of red blood cells is called haemolytic anaemia, and can be due to infection with bacteria, viruses, protozoa, poisoning or immunological reaction.

< previous page

page_107

next page >

< previous page

page_108

next page > Page 108

Poor-quality feed can cause the bone marrow to cut the output of red blood cells and haemoglobin. Normal production and replacement of red blood cells depends heavily on good nutrition and proper health. The most common causes of a low red blood cell count are a heavy redworm (Strongylus vulgaris) infestation and poor-quality feed. The lack of copper, iron, folic acid and vitamin E will result in red blood cells deficient in haemoglobin. Treatment Anaemia can only be alleviated by treating its cause first. If bleeding internally, the source should be located and bleeding stopped if possible. A blood transfusion may be required if the packed cell volume (PCV) falls below 1012%. Poor nutrition, parasite burdens, viral and bacterial infections and haemorrhage must be dealt with before the anaemia can be treated. For immediate treatment, a supplement containing iron and B-group vitamins can be fed, and injections of vitamin B12 act as a haemoglobin booster. Anaemia can usually be prevented by good stable management, including a regular worming programme and a goodquality, balanced diet.

< previous page

page_108

next page >

< previous page

page_109

next page > Page 109

10 Respiratory Problems Respiratory problems are notorious for causing poor performance in equine athletes. A compromised respiratory system will result in reduced oxygen flow to the muscles. Management of stabled horses needs to be of a high standard to maintain the respiratory health of these horses. Chronic Obstructive Pulmonary Disease (COPD) Breathing is essential for life, and any defect in the horse's respiratory system can dramatically decrease performance, especially in horses working at maximum effort. It has been long recognised that horses living in dusty stables cough, and if forced to continue to work in these conditions eventually become 'broken-winded'. Causes and Symptoms Research work has shown that some horses are sensitive to the spores of fungi found in large numbers in badly conserved hay and straw, notably Aspergillus fumigatus and Micropolyspora faeni. When these spores are inhaled, they stimulate a normal defence mechanism, i.e. the bronchi and bronchioles leading to the lungs constrict in an attempt to stop the particles penetrating any further into the lungs. This is usually accompanied by a cough, causing expulsion of the spores, and then the bronchi return to their normal diameter. However, in horses that have become sensitised to fungal spores the bronchioles fail to return to normal, and substances released by the body cause an inflammatory reaction, swelling (oedema) and increased mucus production, all of which serve to reduce the diameter of the airways in the lung. This is known as 'small airway obstruction' or SAO (Fig. 10.1). When the airways are narrowed, there is increased resistance to airflow and breathing out takes longer; the next inhalation may have started before all the previous breath has been expelled.

< previous page

page_109

next page >

< previous page

page_110

next page > Page 110

Fig. 10.1 Normal and obstructed small air passages of the lung. This means that air is trapped in the alveoli which overinflate, a condition characteristic of broken wind (emphysema). The consequences of these effects on the horse can be very serious. Instead of the respiratory movements being barely noticeable, the resting horse has to make a physical effort to expel the inhaled air. This results in a wheeze, a double exhalatory effort and eventually the

< previous page

page_110

next page >

< previous page

page_111

next page > Page 111

development of the 'heaves' line, which runs between the end of the ribs and the belly (Fig. 10.2) and is due to the overdevelopment of the muscles controlling respiration hence the old name 'heaves' for this condition. The horse will also develop a chronic harsh cough and have an increased respiration rate. Exercise tolerance, i.e. the horse's performance, may be dramatically reduced.

Fig. 10.2 The 'heaves' line. Stable dust also contains micro-organisms, which can cause inflammation of the bronchi (bronchitis) and bronchioles (bronchiolitis), and fine dust particles which irritate and damage the lining of the tubes, causing coughing. Treatments Fortunately, COPD is reversible if treated promptly, and with the correct combination of stable management and drug therapy the horse can return to full work. Many horses show a full recovery when turned out permanently for 3 months. However, once rehoused in a stable environment, symptoms often return. Plenty of fresh air and turn-out is highly beneficial for these horses. For horses who must be stabled due to training, stable management must be such that the horse lives in as dust-free an environment as possible. This involves three aspects:

< previous page

page_111

next page >

< previous page

page_112

next page > Page 112

ventilation bedding feeding. A dry, clean, airy stable is the first consideration. The ventilation should be such that there are six complete air changes every hour, which means that there should be inlet and high-level outlet air vents other than the door. Stables must be kept free from dust and cobwebs, and preferably should not be down-wind of dusty areas such as barns. Straw is not an acceptable bedding for a horse afflicted with COPD and alternatives such as shredded paper, peat or shavings should be used. All wet bedding must be removed, because after several days urine-soaked paper can become an ideal medium for fungal growth and thus the production of spores. Deep-litter bedding would not be suitable for a COPD horse. Complete cubes and haylage provide spore-free alternatives to hay. Both are expensive ways of feeding, and cubes can lead to boredom and problems due to lack of roughage in the diet. Haylage must be stored carefully and used within 3 days of opening. Soaking hay is a successful, if time-consuming, way of feeding the allergic horse, provided it is good-quality hay it should not be used as way of making poor-quality hay palatable. Ideally, hay should be soaked by full immersion in water for a minimum of 30 minutes. Soaking for longer than a couple of hours is now thought to be detrimental and adversely affects the quality of the hay. Hay and straw carried past the affected horse's stable or stored in close proximity can start symptoms, so ideally the COPD horse should be stabled separately. Drug Therapy This will depend upon the major cause of the problem, i.e. whether it is bronchospasm narrowing the airways or whether it is exudate, or a combination of both factors. Three main groups of drugs are used: Bronchodilators, e.g. clenbuterol. These are effective, relieving symptoms of bronchospasm within half an hour. Clenbuterol may be given intravenously in some more severe cases or via inhalation. Clenbuterol syrup is now available for oral administration. Anti-allergy, e.g. sodium cromoglycate. This is administered by inhalation and acts by reducing histamine release. It is not effective in alleviating symptoms which are already present.

< previous page

page_112

next page >

< previous page

page_113

next page > Page 113

Mucolytics, e.g. bromhexine. These decrease the viscosity of the mucus produced by the bronchioles, making it easier for the horse to expel the exudate through coughing. Respiratory Viruses. Viruses are very small living particles which infect and cause disease in man, animals and plants. Unlike bacteria, they are not killed by antibiotics. There are three major viruses causing respiratory disease in horses: influenza equine herpes virus 1 (rhinopneumonitis) adenovirus. Typically, these viruses infect a number of horses at the same time. Many older horses have experienced the disease and are resistant to reinfection, so respiratory disease primarily affects the young horse, making 'the virus' of particular importance in racing stables. However, if a mutant (genetically changed) version of the virus appears it will affect all horses, because even the older horses will have no resistance to it. The symptoms caused by the different viruses are very similar. Diagnosis is made by examining antibody titres in paired serum samples at 10-day intervals. The virus may be isolated from nasal swabs. Symptoms include a short fever (39 to 41°C/102 to 106°F) lasting 1 to 3 days, depression and lack of appetite, a nasal discharge and a cough. The virus invades the lining cells of the windpipe, nose and lungs, causing acute inflammation. Antibiotics are not effective against viruses but can be used as supportive treatment to prevent secondary bacterial infection of the weakened horse. The horse should be confined to its box (which should be clean and airy) and kept warm until its own body defence mechanisms overcome the viral assault. It must be remembered that the internal damage may still not be healed until 3 weeks after the clinical signs of illness have gone. A rule of thumb is to give the horse a week off work for every day that it has had a fever. If the horse is worked too soon, before the cough has completely subsided, the ulcers in the lining of the nose and throat caused by the virus become infected. This can cause high fever, a pus-like nasal discharge, and even pleurisy if the horse is stressed. If permanent damage is to be avoided, a horse may need at least 3 to 4 weeks' rest after even mild respiratory infections.

< previous page

page_113

next page >

< previous page

page_114

next page > Page 114

Influenza Equine influenza is a highly contagious respiratory disease caused by a myxovirus, of which there are several types. The 'flu can vary from being mild (almost unnoticeable) to severe, depending on the age and condition of the affected horse and the type of virus. After a short incubation period, the horse develops a temperature lasting 1 to 3 days and a characteristic cough. This starts as a dry, hacking cough soon after the onset of fever, then becomes moist and less frequent, persisting for several weeks. The horse may also have a watery nasal discharge and show weakness, stiffness, loss of appetite and depression lasting 2 to 7 days. Secondary bacterial infection is rare but can occur, leading to pneumonia, chronic bronchitis, emphysema and myocarditis. 'Flu can be positively diagnosed by the increasing level of antibodies in the blood between the acute and the convalescent stage. Vaccines are available, and they have considerably reduced the incidence and severity of 'flu attacks. Vaccination is advisable for all horses that attend events such as hunting, where strange animals are brought together, and is compulsory for many equestrian sports including racing, horse trials and affiliated showjumping. There is debate about the effects of vaccinating horses against equine influenza; horses may experience adverse reactions, and there is a feeling that vaccination damages the horse's natural immunity. In 1999 the British Dressage Association ruled that vaccination would no longer be compulsory for horses to become registered and compete. However, most veterinary surgeons strongly recommend that a horse is fully vaccinated with licensed equine influenza vaccines. Unvaccinated horses not only run a greater risk of contracting the disease themselves but also increase the risk of spreading 'flu to other horses. Following vaccination the horse should not be subjected to any stress for 2 days. Vaccination Schedules These tend to vary between equine organisations and this can cause some confusion. Also the vaccine manufacturers recommend different schedules following their latest research and clinical trials' results. Adhering to the manufacturers' recommendations will provide the most protection against influenza and will also satisfy FEI, Jockey Club and most racecourse regulations. Most equine influenza vaccinations also contain the tetanus vaccine, and following the influenza

< previous page

page_114

next page >

< previous page

page_115

next page > Page 115

vaccination schedule will protect horses against tetanus if the combined vaccine is used. If a separate vaccine for tetanus is preferred then the schedule is as follows: Tetanus Vaccination Schedule Primary course: two injections 2192 days apart First booster: within 365 days of second injection Following boosters: once every 25 years. FEI and Jockey Club Regulations state that injections cannot be given in the 7 days immediately before a competition or entry into a competition stables. Equine Influenza Vaccination Schedule (1) Manufacturers' recommendations: Primary course: two injections 2842 days apart First booster: 168 after second primary injection Following boosters: annually within 365 days or previous booster. In high-risk groups such as competing horses or during an outbreak boosters should be given every 6 months. (2) FEI vaccination schedule: Primary course: two injections 2192 days apart Boosters: annually within 365 days of second primary injection. (3) Jockey Club vaccinations schedule: Primary course: two injections 2192 days apart First booster: within 150215 days of second primary injection Following boosters: annually within 365 days of previous booster. Advised to be given more frequently during an outbreak. Competitors should note that to gain entry to many competitions and racetrack stables the horse's vaccination certificate will be checked for intervals between vaccinations right back to the primary vaccination. Equine Herpes Virus 1 (Rhinopneumonitis) This virus causes acute respiratory disease symptoms similar to those of equine influenza. Secondary bacterial infection may lead to a pus-

< previous page

page_115

next page >

< previous page

page_116

next page > Page 116

like nasal discharge in more serious cases, but the horse usually recovers in 10 to 21 days. Herpes myelitis may result in posterior inco-ordination or even hind limb paralysis. This virus may also result in the 'loss of performance syndrome', which may last at least 10 days. Adenovirus This virus affects the upper respiratory tract and conjunctiva, causing a mucus discharge from the nose and eyes accompanied by coughing, fever, etc. This can be fatal in foals. Equine herpes virus 1 and adenovirus may occur in a mild form, called 'snotty nose' when the fever goes unnoticed and only the nasal discharge is seen. This is common in foals and yearlings and may continue for months, but is rare in adults. Exercise-Induced Pulmonary Haemorrhage (EIPH) (Also Known As Epistaxis) Horses that suffer from EIPH bleed from one or both nostrils. The source of the bleeding may be the mucous membrane of the nasal passage, throat, gutteral pouch or lungs, and bleeding may occur for several reasons: (1) Gutteral pouch infection, usually fungal. (2) If for any reason the horse holds its breath or breathes irregularly, air will not move smoothly and may remain trapped in the lungs. This causes the alveoli to inflate, slowing the flow of blood out of the lungs. Back pressure develops in the veins, and the walls of the blood vessels become damaged and bleed into the lungs. However, the theories on the aetiology of idiopathic pulmonary haemorrhage are still wide open. (3) Inadequate recovery time allowed after 'flu attack. The lesions in the respiratory tract bleed when the horse is galloped. (4) Ethmoid haematoma. There is no reliable cure for EIPH although coagulant drugs, vitamin C and antibiotics may help. Rest is always necessary to allow time for lesions to heal. Loss of Performance There are many other viruses which can affect horses, and although they may not have such dramatic and recognisable symptoms they are

< previous page

page_116

next page >

< previous page

page_117

next page > Page 117

the cause of horses not performing as well as expected (loss of performance). Many racehorse trainers have their horses regularly blood-tested and will not race an animal 'if its blood is not right'. However, it is a widely held misconception that blood-testing helps identify whether a horse has a viral infection before the clinical symptoms appear. The parameters examined in the blood test are white cell total and differential counts. These are a reflection of the horse's response to the infection, and thus there is always some time lapse.

< previous page

page_117

next page >

< previous page

page_118

next page > Page 118

11 Heatstroke and Dehydration. Great Britain may be considered as having about the best climate in the world as far as competing horses are concerned something to be borne in mind during the occasional long winter and inclement spring. Hot and humid conditions place extra stress on performing horses. When horses exercise they produce heat at a high rate and this needs to be dissipated. Horses produce copious amounts of sweat which helps to cool them down. However, this also increases the risk of dehydration during intense exercise. All horses undertaking exercise in hot and humid conditions will be equally at risk. In 1994, the Animal Health Trust undertook a project to assess the effects of heat and humidity on event horses. This was undertaken to minimise problems for horses competing in the three-day event in the 1996 Olympic Games in Atlanta. From previous studies it was clear that normal three-day event competitions under hot or hot and humid conditions could lead to severe hyperthermia and dehydration, with consequent welfare implications for the horses involved. Later studies then aimed at assessing preferred methods of cooling horses, acclimatising them to a new environment, and accurate assessment of actual environmental conditions. Following these studies, recommendations were made to teams travelling to the Olympics in Atlanta. These included: Moving all horses competing in equestrian disciplines to Atlanta 3 weeks before their events. This allowed 1 week to recover from the journey and 2 weeks to acclimatise. Assessment of environmental conditions was undertaken using an index known as wet bulb globe temperature (WBGT). This takes into account wind and solar radiation as well as air temperature and humidity. The WBGT, once calculated, could be used by the Grand Jury to modify the speed and endurance test where appropriate. It was commonly believed that cooling horses with cold water

< previous page

page_118

next page >

< previous page

page_119

next page > Page 119

would result in vasoconstriction. This in turn would reduce the amount of heat lost from the horse's skin, i.e. the opposite of the initial intention. It has now been shown that horses cooled with cold water after intense exercise show a faster recovery in normal body temperature, respiratory and heart rates than those cooled with warm water. In the 1996 Olympic Games at Atlanta, horses were cooled with ice-cold water (-4°C) and there were no incidences of heat exhaustion in any of the competing horses. Heat Loss During exertion a great deal of heat is generated in muscles. At a heart rate of 140 to 160 per minute, a 1°C (2°F) temperature rise every 3 minutes would be generated in the muscle if there were no heat regulation in the body. Normally, however, the horse's body temperature is maintained within a very narrow range by sensors situated in the body which stimulate protective reflexes to raise or lower temperature. If extreme conditions cause these controls to become inadequate and the body temperature becomes too high or too low, the horse becomes ill. If the conditions persist, the horse may die. Methods of Heat Loss There are three main ways in which the horse can lose heat: (1) The skin. The circulatory system takes heat from the muscle to the surface; the superficial blood vessels dilate so that more blood can circulate close to the skin and heat is lost to the environment (Fig. 11.1). (2) The lungs. The air breathed out is relatively warm and has a high water content higher than that breathed in; it is a useful form of heat loss and in those animals that are unable to sweat it is the major method of losing heat, e.g. dogs panting. Horses only pant if conditions are extreme and cooling from the skin is ineffective. They may pant up to 200 times per minute to increase heat loss. (3) Sweating. Sweating involves the evaporation of liquid, excreted from the sweat glands, from the surface of the animal (Fig. 11.1). Heat is used up when moisture evaporates into the air, so that the surface from which it has evaporated in this case the horse's skin is always left cooler. Sweating is a very

< previous page

page_119

next page >

< previous page

page_120

next page > Page 120

Fig. 11.1 Section through the skin.

< previous page

page_120

next page >

< previous page

next page >

page_121

Page 121 efficient cooling mechanism. Horses have evolved into animals who sweat more than any other. All these processes take place more efficiently when the air temperature and humidity are low and the air moves, i.e. there is a breeze. Any insulating materials, such as rugs, tack, a thick coat and fat, make heat loss difficult. If the horse's coat is wet, i.e. there is visible sweating, then effective heat loss is not taking place because the moisture is not evaporating quickly enough. Humid conditions, where the air already has a high water content, make effective sweating difficult and can be a serious threat to the competing horse. Dehydration through Sweating Horse sweat is very rich in electrolytes, which are mineral salts contained in blood plasma (the liquid part of the blood from which sweat is derived). Electrolytes are minerals that become electrically charged ions when dissolved: Na+ (sodium), Cl- (chloride), (K+ potassium) and (Mg2+ magnesium). They must be present in the body in the correct proportions so that normal metabolism can continue. Horse sweat has an electrolyte content ten times that of human sweat (Table 11.1) and is also more concentrated than blood plasma in these salts. This means that while in the human marathon runner water replacement is most important, in the horse it is also very important to ensure replacement of electrolytes. Table 11.1 The composition of sweat. Sodium (Na) (g/litre)

Potassium (K) (g/litre)

Chloride (Cl) (g/litre)

Plasma

140

3.54.5

100

Human sweat

1060

45

1060

Horse sweat

130190

2050

160190

Horse sweat is also very high in protein 15 to 20 grams per litre compared with blood plasma which contains 60 grams per litre. However, this protein is only lost during the early stages of sweating. It is stored in the sweat glands and has detergent-like properties, i.e. it allows the sweat to spread along the hair, causing more effective

< previous page

page_121

next page >

< previous page

page_122

next page > Page 122

evaporation. This protein causes the white lather seen on profusely sweating horses, e.g. racehorses parading in the ring. The amounts of water and electrolytes in the body are controlled by the kidney altering the amount and composition of the urine. Losses of water and electrolytes through sweating and panting are beyond the control of the kidney, and must be replaced through eating and drinking. A horse can lose 15 litres (about 3 gallons) of sweat in an hour of hard work in hot conditions, and may become dehydrated if this is not replaced. The horse has a great problem in maintaining normal physiological conditions inside the body when working in hot, humid weather. Trainers who are lucky enough to own or use a weighbridge are able to weigh horses before and after exercise. This gives an indication of fluid loss. One kilogram of weight lost equates to 1 litre of fluid. The Effects of Fluid and Electrolyte Loss By the time a horse has sweated 22 litres (5 gallons) of moisture which it has not replaced by drinking, it will be suffering from dehydration. The fluid is lost from blood plasma (extracellular fluid) and from inside the cells (intracellular fluid). This upsets cell function, which means that tissue and organ function will also be impaired. The blood supply will have diminished, and the blood will be more concentrated and thicker. This has four effects: (1) As blood volume falls, there is less sweating and an increase in body temperature. (2) The oxygen-carrying capacity of the blood is diminished. The muscles will become increasingly short of oxygen, and in order to keep functioning an alternative source of energy is required. This is obtained by breaking down energy stores in the muscle without the use of oxygen (anerobic respiration). Lactic acid is released, resulting in failure and possibly destruction of muscle fibres. This is manifested as tying-up. The horse may also exhibit colicky pains. (3) As cooling from the skin becomes ineffective, the horse will begin to pant. If the respiration rate is greater than the pulse rate, the horse is suffering from heat stress, i.e. there is too much heat in the body, and veterinary help should be sought. (4) Sweating causes loss of electrolytes, and this is responsible for some of the signs of dehydration and exhaustion including quivering of the muscles and 'thumps' (synchronous dia-

< previous page

page_122

next page >

< previous page

page_123

next page > Page 123

phragmatic flutter), when a horse's heart appears to be beating in its flanks. Temperature A horse's normal temperature is 38°C (100.5°F). During exertion the horse has the ability to store some heat, i.e. the core temperature in the centre of the body rises. It is not uncommon to see temperatures of 39°C (102°F) at the end of Phase C and 39.5°C (103°F) at the end of Phase D of a three-day event. There is no cause for concern unless the temperature is greater than 39.5°C (103°F) in very hot weather, or the horse's temperature is static or rising. A bright, alert horse would be allowed to start Phase D at this level. A horse with a temperature of 40°C (104°F) plus should not on any account be allowed to continue. Remember that these are all rectal temperatures. The core temperature will be about 2°C higher. Muscle fibres start to die at about 42°C (108°F), any horse with a temperature higher than this will suffer muscle damage if indeed it survives. Heat Exhaustion This includes exhaustion and heat stress. Prolonged exercise undertaken in hot and humid conditions will eventually result in heat stress or exhaustion. Exhaustion occurs when the rectal temperature reaches 43°C (109.5°F). The heart and respiratory rates fail to recover during the veterinary check, and irregularities in heartbeat may be detected. Synchronous diaphragmatic flutter may have begun. The horse is dehydrated and depressed. Horses showing these symptoms should not undergo any further exercise. They should be placed in shade and cold-hosed. If the horse will drink, small amounts of water may be offered. Severe cases will require nasogastric administration of electrolytes. The route used may be intravenous if the horse is recumbent. Following cooling, horses should not be transported within 24 hours of the incident, as further adverse reactions may occur. Heat Stress This occurs when the horse's normal thermoregulatory pathways fail to dissipate heat, leading to an increase in its rectal temperature to 43°C (109.5°F). The horse becomes weak and is unwilling to carry on

< previous page

page_123

next page >

< previous page

page_124

next page > Page 124

exercising or competing. These horses should be cooled down, placed in shade and given fluids if appropriate. Assessment of Dehydration Dehydration can be assessed by: • the pinch test • biochemically. If a fold of skin is picked up, and does not return in a normal supple manner but remains standing up, the horse is dehydrated. This is easiest to test on the shoulder or neck. Dehydration can be detected by measuring protein in the plasma. Obviously, a blood test takes time and this is not always a satisfactory method. Reducing the Occurrence of Heatstroke, Exhaustion and Dehydration. It is essential that every rider is aware of the symptoms of dehydration and exhaustion. Some of the very severe signs have already been mentioned, e.g. panting, quivering of the muscles and 'thumps'. In addition, all tiredness is accompanied by general listlessness and a lack of inclination to eat or graze. A horse whose muscles are seriously short of oxygen may breathe so slowly that he takes less than one breath per stride; a horse that it is also overheated may take several short breaths between long breaths until oxygen needs are met, and then panting may be almost continual. Dehydration is indicated by patchy thick sweat, which is very serious because the animal will then be at risk from overheating. There will also be a loss of the normal colour from the membranes of the eyes and gums. If a finger is pressed to the gum, the blanched area made takes a longer time than normal to re-colour. This indicates that the blood is too thick to circulate through the small blood vessels and that rate of flow has slowed down. If a fold of skin on the neck pinched between finger and thumb takes more than 5 seconds to flatten out, this indicates that the horse is moderately to severely dehydrated riders can use this test as they go along. Should any of these signs become apparent, the rider should seek veterinary advice as quickly as possible. The best way to avoid these problems can be considered by looking at:

< previous page

page_124

next page >

< previous page

page_125

next page > Page 125

the horse its preparation its management during the competition. The Horse The horse should be the right type for the job required of it. Many long-distance horses are Arabs or of Arab breeding, and the most successful horses have only been about 152cm (15 hands) high. In Britain we had the perfect long-distance horse in the Norfolk, but recently allowed it to die out. The best three-day event horses tend to be Thoroughbred or 7/8ths Thoroughbred, lean athletic types with flowing, economical action. Preparation of the Horse The object of preparation is to produce an animal athletically capable of the task, mentally content and physiologically in a normal state. However, the horse may be subject to dehydration even during training. The onset of a shortage of water can be insidious for example, it may be brought about by standing in a hot lorry for a few hours. Fit horses should have water made available to them every hour, particularly if they have worked first. Care should be taken that the horse drinks the water offered to it during its stay at a competition. This may mean bringing water from home, or adding common salt or beet molasses to the feed, which may help the reluctant horse to drink. Management of the Horse The management of the horse immediately before and during the competition is of great importance. The eventer on cross-country day should have water freely available until an hour or so before Phase A. Horses' stomachs empty very quickly, and it is not necessary to withhold water for very long before starting. If a horse has free access to fresh water in its box, it is unlikely to drink too much at once. If possible, avoid hurrying your horse into the box at the end of Phase C, as it will have much more recovering to do and the halt loses much of its value. While remembering to give the inspection panel 25 metres' trot as the box is entered, it is best to walk the previous 100 metres or so. When in the box, the horse should not be allowed to stand and stiffen up. Under normal conditions, the neck and extremities should be

< previous page

page_125

next page >

< previous page

page_126

next page > Page 126

sponged with cool water which is allowed to evaporate. Remember that it is not the application of water that cools the horse but its evaporation from the skin. As soon as the horse is dry, water should be re-applied. Under hot conditions, water should be splashed over all the body except the croup and loins, where the result may be stiffening and even tying-up of the back muscles. Ice should also be available under severe conditions and applied to the head, throat and inside legs, where it can cool the blood running through surface vessels. A mixture of spirit and water cools and cleans very effectively. A dry numnah should be fitted to the saddle if the other numnah is soaked through with sweat. A small mouthful of water may be offered more will merely be an unwanted burden in the stomach during Phase D as water will not be absorbed from the stomach to a significant degree during the crosscountry phase or the horse's mouth may be sponged out (Fig. 11.2). After the application of these precautions, your horse has a better chance of being ready to gallop over a demanding course with a smaller risk of suffering from the heat. After the cross-country, the horse should be treated in much the

Fig. 11.2 Sponging out a horse's mouth.

< previous page

page_126

next page >

< previous page

page_127

next page > Page 127

same way as during the 10-minute halt. The importance of walking the horse cannot be too strongly stressed this keeps the blood flowing through the body, helping disperse metabolic waste products formed during galloping, and also helps the animal cool. The horse should be sponged down, walked until it is dry, sponged again and walked slowly until the pulse and respiration rates are approaching normal. Water may be safely offered at a rate of 4 litres (1 gallon) every 15 minutes (this is discussed in Chapter 15). However, it must be remembered that a tired and possibly dehydrated horse may take a long time (up to a minute) to decide to drink, so always wait when offering the horse water and do not take it away too quickly. If the climate is very hot and the horse is not accustomed to the degree of heat, e.g. horses from the U.K. competing in Kentucky or California, dehydration may set in before the competition has started. It may be necessary to cool the stable by waterspray on the roof and fans at the door to create a breeze. Electrolytes should also be used, and these will be discussed later. Keeping cool and the provision of water are also very important for the endurance horse. Before the ride, water must be freely available in the box and paddock. There will then be no need for the horse to drink excessively before a feed or before work, nor will it start work thirsty. During competition, the horse should ideally never become excessively thirsty. However, this is not always possible due to the speed, the route or the weather, and it may become impossible to keep the horse so well watered that it arrives at each drinking place in a fit state to drink all it needs without pause. In these cases it is essential that the horse should remain by the water, drinking at intervals until the thirst is quenched. If the thirst is not quenched, the horse will be even more thirsty by the time the next drinking place is reached. It is advised that drinks of 15 to 20 swallows (about 2 litres or 4 pints) followed by a pause of 1 minute should be allowed. The horse should then be ridden at walk for several hundred metres until the water in the stomach has had time to warm up. Provided these methods are followed, there is no danger in giving a hot horse cold water. At a rest halt, the horse should be washed down as previously described, taking great care to clean properly under the saddle and girth. The legs and saddle area may be rubbed with methylated spirit, which restores circulation and quickly evaporates, leaving the surface fresh and cool. Nostrils, eyes and dock should also be well sponged with clean water. If the horse has been allowed to drink properly during the ride, it

< previous page

page_127

next page >

< previous page

page_128

next page > Page 128

should not arrive at the halt excessively thirsty and should be allowed 2 to 3 litres (4 to 6 pints) every 5 minutes until the thirst is quenched. If the horse is kept moving there is no danger in giving cold water, but most riders prefer to give water with the chill taken off it (known as 'chilled water'). Electrolytes Electrolytes are powders or liquids given in solution in the drinking water before, during and after competition to replace electrolytes lost during sweating. A horse's diet may, as previously mentioned, be low in salt, and if the horse sweats it may suffer a sodium chloride deficiency. This may be partially overcome by providing a self-feed salt lick this is not sufficient for horses in very hard work, but it can be regarded as insurance to top up a horse's salt levels. After a competition, it may take 5 to 6 days to replace the potassium lost during heavy sweating. Horses receiving plenty of pasture or forage are unlikely to be deficient in potassium. Hays typically contain between 10 and 20 g potassium per kilogram. Unfortunately, forage tends to be low in sodium and a salt lick should be provided. Although, in theory, feeding plenty of good quality forage with a salt lick should provide adequate electrolytes, in practice this is often not the case. Racehorses, for example, rarely receive high forage rations! Electrolyte supplementation is therefore important for sustained athletic performance and quick post-exercise recovery. There are several products on the market; some contain more sugar than salt! The horse-owner should look at individual products to assess which electrolytes are supplied, or consult a nutritionist or vet. An alternative would be to offer two-thirds salt (NaCl) to one-third potassium chloride (KCl) free choice.

< previous page

page_128

next page >

< previous page

page_129

next page > Page 129

12 Internal Parasites It is important for horse-owners to appreciate that no horse can be expected to perform at maximum levels when suffering from a worm burden or the damage caused by previous parasite infestations. A regular worming programme from 6-weeks old continuing throughout the horse's life is essential. The horse is host to a wide variety of internal parasites, only the most important of which will be discussed here namely large and small roundworms (strongyles), ascarids, bots and lungworm as these are the ones which tend to affect performance. Strongyles There are two groups of strongyles: the large strongyles and the small strongyles. The redworm (Strongylus vulgaris), one of the large strongyles, causes the most severe damage of all the internal parasites. The larval stages of the worm travel throughout the horse's body. First, they burrow through the intestine wall and enter the small arterioles of the blood circulation, then migrate through the arteries, travelling against the flow of the blood. Larvae may enter the aorta and travel to the heart, causing valve damage, or enter the renal artery (supplying the kidney), but the majority tend to stay in the anterior mesenteric artery which supplies the intestines. Here, the larvae attach to the arterial walls, causing inflammation and a weakening and bulging of the wall called an aneurysm. If there is a lot of irritation, the artery may become blocked due to the build-up of larvae and blood clots; this results in part of the intestine being starved of its blood supply and dying (infarction). Food is unable to pass normally through the dead portion of the gut, resulting in colic. Redworm larvae are thought to be responsible for the majority of cases of spasmodic colic in horses. The life-cycle of the redworm is very long, ingestion of larvae to the appearance of adults in the large intestine taking 6 to 12 months (Fig. 12.1). In the horse's intestine, the female worm lays eggs which pass

< previous page

page_129

next page >

< previous page

page_130

next page > Page 130

Fig. 12.1 The life-cycle of the redworm (Strongylus vulgaris). The ingested larvae enter the arteries supplying the gut and migrate up the vessels to the cranial mesenteric artery. After a period in that vessel they migrate down the arteries to enter the large intestine and become egg-laying adults. out with the dung on to pasture; the eggs hatch to give stage 1 larvae. These feed and become stage 2 larvae which in turn become stage 3 infective larvae these, when swallowed by the horse, can complete their life-cycle. The larvae then migrate through the horse's body as described, returning to the large intestine as egg-laying adults. The adult worm can cause damage by sucking blood from the intestine and causing anaemia, ulceration, bleeding, colic or diarrhoea. Small strongyles are not as destructive because their larvae do not travel outside the wall of the intestine. The adult worm does not usually suck blood and the major damage is caused by the ulcers left in the intestine wall after the larvae hatch from it. Small strongyles mature in 6 to 12 weeks. Ascarids (Parascaris Equorum) Known as the whiteworm, this is the largest roundworm found in horses, the male reaching up to 30 cm (12 in) in length and being as thick as a pencil. The adult worm lives in the small intestine, where the female lays eggs which pass out in the droppings. Infective larvae develop; they are swallowed by the grazing horse and pass into the intestines. The larvae burrow through the intestinal wall and are carried to the heart, lungs and liver in the bloodstream. After a period

< previous page

page_130

next page >

< previous page

page_131

next page > Page 131

of growth and development, causing damage in these organs, larvae invade the windpipe and are coughed up and swallowed. Larvae pass through the stomach to the intestines where they grow into adults, completing the cycle in about 12 weeks (Fig. 12.2). A female can contain 27 million eggs and lay 200,000 eggs a day. The eggs can live for months and are resistant to many chemicals.

Fig. 12.2 The life-cycle of the ascarid. The eggs are picked up with grass, swallowed, and pass down the oesophagus to the stomach and small intestine. They migrate from the intestine through the liver and lung, are coughed up into the throat and reswallowed. Once again in the small intestine they develop into egg-laying adults. Ascarid infection is most common in foals and young horses that have not yet acquired resistance to them. Due to the persistence of the eggs, this year's foals can pass out eggs that will infect next year's foals. Ideally, young foals should be turned out on 'clean' pasture, i.e. grass that has not been grazed by horses during the previous 12 months. Ascarids cause unthriftiness, lung damage and occasionally rupture of the gut due to the massive build-up of worms. This is fatal. Ascarid infections are fairly easy to control; foals should be wormed at 6-weeks old and then at 4 to 6 week intervals.

< previous page

page_131

next page >

< previous page

page_132

next page > Page 132

Bots These are the larvae of the botfly (Gastrophilus) which live in the stomach of the horse. The fly is about 1.3 cm (0.5 inches) long and beelike, although it cannot suck, bite or feed because its mouthparts are degenerate. The fly is active in early summer and September, making a humming sound as it flies, and lays its yellow eggs on the hair of the throat, legs or on the lips. Each egg hatches in 9 to 12 days, but the first larvae cannot develop until they are licked into the warm, moist horse's mouth. In the mouth the larvae burrow into the cheek or tongue for 20 to 30 days before migrating to the stomach. The second and third stage larvae (bot maggots) grow in the stomach living on the host's food for about 12 months. They then pass out with the droppings, the maggots pupate for about 3 weeks and the adult fly emerges, thus completing the cycle. The adult fly can cause horses to panic and gallop about. The maggots can cause inflamed ulcers in the stomach and thus disrupt digestion. Lungworm (Dictyocaulus Arnfieldi). These are roundworms living in the air passages of the lungs where they lay their eggs. These are coughed up and swallowed and pass out in the droppings where they hatch and are picked up by another horse. Once swallowed, the larvae bore through the intestinal wall and enter the lymph stream. Venous blood carries them through the heart to the lungs, where they develop into egg-laying adults. The worm irritates and inflames the bronchi of the lungs, causing bronchitis and a chronic cough. Migrating larvae can cause scouring. Donkeys are capable of carrying large numbers of lungworms without showing any symptoms and should not be allowed to graze with horses unless they have been checked to see if they are carriers, and then treated. Diagnosis of Worm Infestation Although a horse may be regularly wormed, it should still be checked at intervals for the presence of a worm burden because the parasites may have built up resistance to the chemical being used. This check can be done in two ways: a worm egg count in the dung or a blood test.

< previous page

page_132

next page >

< previous page

page_133

next page > Page 133

Egg Counts A sample of fresh dung is looked at under the microscope and the number of worm eggs counted. The presence of even small numbers of eggs in the dung indicates large numbers of egg-laying adults in the intestines. This test can, however, be misleading if a horse has been recently wormed there will be no eggs in the droppings, but there may still be many larvae migrating through the tissues, providing a backup ready to enter the intestines and mature. The horse is not free of these parasites: the dangerous larvae are still there. Faecal egg counts are measured as eggs per gram (EPG). If a faecal egg count gave a result of 300 EPG, and the horse produces approximately 5 kg (5000 g) of droppings per day, then 300 × 5000 = 1 500 000 eggs per day may be shed onto pasture when the horse is turned out. In the stable, these droppings will be collected and removed. Good pasture management should also include collection and removal of droppings. Blood Tests The presence of migrating larvae in the tissues will cause changes in the white blood cell numbers. In particular, eosinophil numbers increase. Eosinophils multiply in allergies; an allergy is an intolerance to foreign protein, so they increase when there is a worm burden. Eosinophil numbers will not return to normal until the migrating larval stages have been removed. However, eosinophils will increase in other allergic reactions and it may be necessary to look at the serum protein levels. Normally the albumin:globulin ratio is about 1.0:0.7, 3 g/100 ml albumin and 2.1 g/100 ml globulin. When there is worm infestation, the globulin levels increase so that the ratio may be reversed, eg. 0.5:1.0. Treatment of Worm Infestation There are many commercial wormers available. The horse-owner must read all labels on commercial products to determine whether they are effective against the adult stages of strongyles and ascarids, and include active ingredients such as: Avermectins Moxidectin and invermectin: effective against migrating larvae at normal dose rates. Not effective against tapeworm. Pyrantel pamoate

< previous page

page_133

next page >

< previous page

page_134

next page > Page 134

Pyrantel tartrate: effective against tapeworm at double the normal dose. Benzimidazoles Thiabendazole Mebendazole Fenbendazole Cambendazole Oxfendazole Oxibendazole Febantel Organophosphates Dichlorvos: effective against bots. Piperazine: not effective against redworm. Phenothiazine: not effective against ascarids. Safety when fed to foals and pregnant mares should be checked if necessary. Intervals between treatments must be carefully gauged. Using ivermectin, the most effective worm control is obtained by worming every 812 weeks. This is essential on grass heavily grazed by horses, but is only really worthwhile if all the animals are wormed. Frequently, a 6 to 8 week worming regime is adopted. This is the minimum time taken for small strongyles to mature and is satisfactory on good grazing which is not horse-sick. Worming spring and autumn is not adequate. It must be remembered that it is equally important to worm the stabled horse at 6 to 8 week intervals. During the horse's spell at grass it will have picked up redworm larvae which may take 12 months to become egg-laying adults. A horse that has been fully stabled for a year may therefore still be carrying a worm burden. This emphasises the long-term effect that an inadequate worming programme at grass can have on the stabled horse all the time redworm larvae are migrating through the horse's body they are causing damage.

< previous page

page_134

next page >

< previous page

page_135

next page > Page 135

PART IV THE HIGH-PERFORMANCE HORSE MANAGEMENT AND TRAINING

< previous page

page_135

next page >

< previous page

page_137

next page > Page 137

13 Nutrition of the Performance Horse The Importance of Feeding Feeding is one of the most critical factors in determining the performance of the horse. The horse-owner relies on the experience of generations of tried and tested feeding regimes, always allowing that horses are notoriously individual in their needs. The aim of this chapter is to extend this experience by combining the highest traditional standards of feeding with sound scientific knowledge, and to explain away some of the myths of feeding from a scientific point of view without losing any practical and proven methods. It might be argued that the methods used by our grandfathers are quite adequate for today's horse without complicating the matter with scientific mumbo-jumbo. However, there are several reasons why the horse-owner should be increasingly aware of the nutritional needs of their horse: Top-class competition horses are subjected to high levels of stress when they are travelled great distances by land, sea and air to competitions. Combined with this, there is prolonged close contact between strange horses when stabled at competitions which can lead to subclinical disease. Feed production technology has changed, involving processing methods which may affect nutrient levels and availability. Unusual, cheaper protein sources may be included in compound feeds and can stimulate an allergic reaction such as urticaria or hives. Intensive farming methods may deplete the soil of its nutrients, leading to deficiencies in the crops grown in that soil. There is increasing anxiety amongst horse-owners because the results of these factors can show up as training problems. A greater

< previous page

page_137

next page >

< previous page

page_138

next page > Page 138

understanding of the nutritional needs of the horse will lead to the formulation of better feed rations and hence healthier horses. The Equine Digestive System The horse is essentially a grazing animal and has evolved as a 'trickle-feeder'. The gut (Fig. 13.1) is designed to cope with the regular intake of small quantities of fibrous food and it needs a constant supply without ever overloading the system.

Fig. 13.1 The alimentary canal of the horse. The Facts behind the Rules. Feed little and often. A stabled horse is in an artificial environment, totally dependent on us for its food and water. To keep the horse's system working efficiently, the feeding regime must mimic nature as closely as possible; hence the first rule of good feeding: feed little and often. The key reason for this is that, for its size, the horse has a relatively small stomach about the size of a rugby ball (Fig. 13.1). The stomach can stretch to accommodate about 13 to 23 litres (3 to 5 gallons) of food, but, due to

< previous page

page_138

next page >

< previous page

page_139

next page > Page 139

the 'J' shape of the stomach it is never more than two-thirds full, i.e. the stomach will hold about 9 to 13 litres (2 to 3 gallons) of food, about two-thirds of a standard water bucket. Allowing for about one-third of the stomach's contents to be water and saliva (the horse produces large quantities of saliva), the amount of food most usefully consumed in one meal is limited to half a bucketful. Any food fed over and above this will push partially digested food out of the stomach into the small intestine. Not only is this wasteful; it is potentially dangerous, too, since this partially treated food may ferment in the small intestine and cause colic. Do not work the horse for 1 hour after feeding. A full stomach will also put pressure on the diaphragm (the muscular layer separating the lungs from the guts), preventing the horse from filling its lungs properly hence the rule do not work fast for 1 hour after feeding (Figs. 13.2 and 13.3). Nobody wants to run a cross-country after Sunday lunch the horse is just the same! Another factor to be considered is that when the horse works some of the blood supply is diverted from the gut to the muscle. Digestion will slow down but food will still pass along the gut,

Fig. 13.2 The digestive system viewed from the side.

< previous page

page_139

next page >

< previous page

page_140

next page > Page 140

Fig. 13.3 The relationship between the stomach, diaphragm and lungs. resulting in the horse getting fewer nutrients out of the food before it is expelled as faeces. This is also the reason why horses and humans may suffer diarrhoea (scouring) after severe exertion. Time of feeding. There has been much work carried out by scientists regarding time of feeding, particularly prior to events. Glucose will peak roughly 13 hours after a concentrate feed and this will produce a rise in the hormone insulin. Insulin will encourage the storage of glucose. If the horse is exercising or competing it should be mobilising its stored glucose, i.e. the opposite of what is actually occurring. Trickle feeding forage will not produce these rapid glucose rises and consequent insulin responses. It has therefore been suggested that horses be fed high grade forage ad libitum before an event, the only disadvantage being the increased gut fill weight and slightly reduced plasma volume. In practice this seems to be inconsequential. Feeding little and often, i.e. by splitting concentrate into five or six feeds per day and adding long chaff to the feeds will help to reduce the insulin response to high grain rations. Water before feeding. When the stomach is full and the horse takes a long drink of water, food may be washed out of the stomach before it has been treated by the gastric juices in the process of digestion. As before, this leads to wastage and possibly colic. So the rule water before feeding is soundly based. However, the extent of this 'washing out' is debatable and modern thinking is that the effect is not as serious as once believed. Due to the 'J' shape of the stomach, it may be that water merely washes over the top of the food causing little harm. To avoid any problems the horse should always have access to fresh clean water except when just about to compete at high speed.

< previous page

page_140

next page >

< previous page

page_141

next page > Page 141

Feed plenty of roughage. The size and nature of the caecum and large intestine (Fig. 13.1) indicate the horse's need for fibre in the diet. There should never be less than 50% roughage in the daily ration, so feed plenty of roughage. Make any changes gradually. The digestion of roughage takes place in the caecum and large intestine, making available to the horse nutrients not available to carnivores, such as dogs, and omnivores, such as humans we would not look very well on a diet of grass. The process that takes place in the caecum and colon is called 'fermentation' and is carried out by a vast population of micro-organisms (bacteria and protozoa). These specialise in fermenting particular parts of the diet and so the number of each type of organism present in the gut will vary depending on what the horse is being fed sudden changes in the diet will result in changes of the pH (acidity) of the gut and poor digestion. This is at best wasteful and at worst may cause diarrhoea or colic; therefore make any changes in the diet gradually. Keep feed ahead of work. The horse is susceptible to problems such as laminitis and azoturia, caused in part by overfeeding, so it is vital that the food level anticipates the workload. Days when the horse is off work must be planned and the ration altered accordingly the day before. Horses laid off due to illness, lameness or bad weather should have their corn feed cut dramatically. If rest days cannot be anticipated, the concentrate feed on the day should be reduced and every effort made to either turn the horse out or lead it out in-hand. Feed according to work done. The horse must be fed a diet which is nutritionally balanced and suitable for that individual and the work it is expected to do. This is, of course, easier said than done, and will be discussed further. An overfed horse can be dangerous to itself and to its rider. Always use good-quality feed. The remaining 'rules' are self-evident, and one of them is always use good-quality feedstuffs. There is an increasing awareness of the horse's susceptibility to dust allergy which can only be avoided by feeding clean, good-quality forage. Pay attention to hygiene. The horse's appetite will be depressed by stale food or dirty mangers, and therefore scrupulous attention must be paid to hygiene and storage facilities. Certain foods have a limited shelf-life, beyond which they may lose palatability and nutritive value, and this must be considered when buying feeds or supplements in bulk.

< previous page

page_141

next page >

< previous page

page_142

next page > Page 142

Keep to regular feeding times. The horse is a herd animal and a creature of habit, and benefits from having regular feeding hours every day. A horse may fret if its feed is not available at the expected time and thus lose condition, which will affect its performance. Feed succulents. The bacteria in the horse's gut are able to synthesise some vitamins but feeding succulents is an excellent way of tempting appetite and providing a natural source of vitamins and minerals. These 'rules' have been adhered to for many years, since long before the anatomy and physiology of the horse's gut were understood. Our increased understanding of what takes place in the horse's body has revealed that these rules are firmly based on scientific fact, which is why they have stood the test of time so admirably. Nutrients Needed for a Healthy Horse To remain in peak condition, the working horse requires a regular supply of about forty nutrients, and to obtain them the horse has to eat suitable food. Nutrients fall into six broad categories: carbohydrate, fat, protein, water, minerals and vitamins. Carbohydrates Carbohydrates include substances such as sugar, starch and fibre, which make up the majority of the horse's diet and are the horse's major source of energy. Sugars These are the simplest forms of carbohydrate, the basic building blocks being monosaccharides or simple sugars, e.g. glucose. It is in the form of glucose that carbohydrates are absorbed through the walls of the small intestine. Glucose is then stored in the horse's body as glycogen and fat which can be converted back to glucose to be used by the muscles during exercise. In excess, carbohydrate is associated with problems such as laminitis, lymphangitis and azoturia. Starch This is the major carbohydrate store in plants. For example, roots and tubers contain 30% starch and cereal grains about 10.5% starch,

< previous page

page_142

next page >

< previous page

page_143

next page > Page 143

making them both very useful sources of carbohydrate for the horse. Sugars and starch are known as soluble carbohydrates; they are broken down rapidly by enzymes in the small intestine, giving the horse a source of 'instant energy'. Cellulose or Fibre (Roughage) This is a complex carbohydrate which is very important in the structure of plant cell walls. Cellulose is known as insoluble carbohydrate and is resistant to enzymic digestion; instead it is broken down by the horse in the caecum and large intestine providing 'slow release' energy. Lignin is a type of fibre which is resistant to breakdown. This is significant because the lignin content increases as the plant ages, and thus mature plants are less digestible and less nutritious. However, fibrous roughage is an essential part of the horse's diet plenty of bulk food is needed to aid breakdown and digestion of other feeds and to maintain the health of the gut. At least 50% of the total diet must be provided as roughage. There appears to be a close link between low fibre diets (such as in racehorses and some competition horses) and gastric ulceration. Plant protein may have a buffering and protective effect in the horse's stomach. Feeding fibre will also reduce behavioural problems in stabled horses and will prevent boredom. Fats and Oils Fat is a concentrated form of energy, and weight for weight provides more than twice the energy of carbohydrate. Excess carbohydrate can be stored as fat, ready for later use as an energy source; it also provides insulation as subcutaneous fat. Most traditional rations contain about 2 to 3% oil. Some feed manufacturers are including up to 10% vegetable oil in their high-performance horse feeds, and some nutritionists are recommending the inclusion of fat in the diet of competition horses, to prevent problems caused by feeding large amounts of cereals. Supplemental fat should be introduced gradually. Protein Protein is concerned with the replacement of muscle tissue lost through natural wastage and the building up of new body tissue. When there are excessive levels of protein in the diet, it can also be used as a source of energy.

< previous page

page_143

next page >

< previous page

page_144

next page > Page 144

Protein is absorbed across the small intestine wall as amino acids, which are the building blocks of body tissue. There are about 23 different amino acids, of which 10 are 'essential' and must be included in the diet. The remainder can be synthesised by the micro-organisms already in the caecum. This means that the proteins in the diet must not only contain the right types of amino acid; the amino acids must also be present in the correct balance, i.e. the horse needs high-quality protein. The quality is reflected by the 'biological value' of the protein, which shows the number of essential amino acids present. Animal protein has a high biological value, but plant protein (e.g. oats and barley) tends to have a low biological value. The amino acids lysine and methionine may be lacking in horses fed a traditional diet of hay and oats; this is why our grandfathers used to include other ingredients such as beans, which are a good source of lysine. The protein levels in the horse's diet must complement the energy content in the ration since optimum feed utilisation depends on a correct protein to energy ratio. This means that although hard work only requires a small increase in protein to make up for a slightly quicker muscle turnover, protein levels must increase as the energy content of the ration increases to maintain the protein to energy ratio. However, feeding very high protein levels to competition horses is wasteful and expensive, because excess protein is broken down and used as an alternative energy source. Overfeeding of protein has even been shown to be detrimental to performance for a number of reasons: Blood urea levels increase which in turn increases urea excretion into the horse's gut. This may cause problems such as enterotoxaemia. Blood ammonia increases, which may cause nervous irritability. There may be higher levels of NH3 in the stable, which could compromise the respiratory system. Excess protein levels will increase the horse's water requirements. Water Water is a vital component of the diet and plays an essential role in nutrition. Nutrients must pass into the horse's system as a solution. Water is needed for this, and is also necessary to produce the large amounts of saliva which help swallowing. A horse can lose nearly all its body fat without major ill effect, but a loss of only 8% of the body water causes illness and a loss of 15% can cause dehydration and heatstroke in competing horses.

< previous page

page_144

next page >

< previous page

page_145

next page > Page 145

Water intake will be affected by several factors including diet, environmental temperature and the amount and type of exercise the horse is undergoing (large amounts of water are lost in sweat). A lack of water will adversely affect feed consumption, a fact which may be important when caring for the sick or tired horse which is reluctant to drink. Clean, wholesome water should be freely available for horses at all times. If this is not possible for example, during work and the horse has become excessively thirsty, it should be offered small amounts of water at intervals until its thirst is quenched. Saliva and Digestive Fluids. In horses, saliva is produced in response to the action of chewing and not in anticipation of a meal. The amount of saliva produced depends on several factors, but a 500 kg horse on a mixed forage/concentrate ration produces about 12 litres per day. A dry ration may result in much more saliva production, as much as 100 litres per day. Other secretions enter the horse's gut also. These include digestive fluids entering the stomach and small intestine, and may total up to 160 litres per day. This fluid comes from the plasma and may lead to a 15% loss in plasma volume. This will be far less for horses who eat little and often, and slowly! Greedy horses should be encouraged to eat slowly by the addition of long chaff to the concentrate feed. The plasma volume is corrected later as water is resorbed from the large intestine. Supplements The pages of any horsey magazine are covered with advertisements for supplements, each one claiming to be the best for your horse. How is the horse-owner to decide which to buy? The object here is not to recommend a particular supplement but to show the horse-owner what to look for in a supplement by describing the job that minerals and vitamins do and indicating where deficiencies may arise. A supplement is not a wonder drug: its task is to make up the difference between shortcomings in the diet and what the horse should be receiving. A supplement, when added to the diet, corrects any imbalance of nutrients whereas an additive is an additional ingredient, for example a probiotic. Supplements may be required when horses are being fed compound feeds at a reduced rate. For example if only 2kg are fed daily and the

< previous page

page_145

next page >

< previous page

page_146

next page > Page 146

manufacturer recommends 4 kg, the horse will only receive half the required vitamins and minerals. Horses on a traditional oat and hay ration will need supplementing. Performance horses require a wide range of vitamins and minerals to perform at their best and maintain health and athletic performance over a period of time. The addition of minerals and vitamins to the diets of these horses should be undertaken with care as they may adversely affect the health and performance of the horse. It is worthwhile asking the advice of a nutritionist if at all possible. Minerals There are about 14 essential minerals which have been shown to be vital to the biological processes which take place in the body. These include the macrominerals required in larger amounts (calcium, phosphorus, sodium, chlorine, potassium, magnesium and sulphur) and the trace minerals required in small amounts (iron, copper, iodine, cobalt, manganese, zinc and selenium). Other minerals such as molybdenum, chromium and fluorine may also play an important role, but this has not yet been fully established. All natural foods contain mineral elements, the proportions varying greatly between different types of food, e.g. cereal grains are low in calcium and magnesium and high in phosphorus, while forages contain more calcium and magnesium but less phosphorus. Foods can only contain the minerals present in the soil in which they are grown, and this can lead to deficiencies in certain areas. Deficiencies also arise as a result of the intensive nature of modern agriculture, which gradually depletes the soil of certain minerals. Horse-owners should be aware of any local soil characteristics which may affect the composition and quality of feedstuffs. The mineral elements which may be inadequate in traditional diets include calcium, phosphorus and magnesium. Sodium, potassium and chloride (sodium chloride is common salt) may be deficient following prolonged exercise as they are lost in sweat. This loss may be made good promptly by the use of electrolyte solutions during and following competitions. The most frequently detected trace element deficiencies are copper, selenium, zinc, manganese and iodine. Diagnosis of deficiency is difficult because there are no specific symptoms. Borderline deficiencies may exist where the horse shows no external signs of illness but is just not performing as well as it should. A competition horse should receive a daily supply of minerals and vitamins so that the body has the chance to function prop-

< previous page

page_146

next page >

< previous page

page_147

next page > Page 147

erly. This becomes even more important when the horse has only limited access to good quality pasture and is under the stress of top competition. Electrolytes These are minerals which form electrically charged ions when dissolved. They include sodium (Na+), chloride (Cl-), potassium (K+) and magnesium (Mg2+). In performance horses, these electrolytes play a vital role in the maintenance of fluid balance. When horses sweat, Na+, K+, Cl- and Mg2+ will all be lost and eventually fatigue will result. These electrolytes must be replaced. The amount of fluid and electrolyte loss through sweat (and urine) will depend upon environmental factors and type of exercise (see Chapter 11). Calcium and Phosphorus Calcium and phosphorus can be considered together as their functions are very closely related. They are the main elements of the apatite crystal which provides strength and stability to the skeleton. Bone acts as a reservoir of both calcium and phosphorus, with the minerals being removed and deposited as necessary, allowing the bone to be remodelled during growth and development, and making up any shortfall in the diet. Calcium is also involved in blood coagulation, lactation, nerve and muscle function; it also acts as an enzyme activator and inhibitor. Bone has a Ca:P ration of 2:1 but the ratio in the whole body is about 1.7:1. Due to its vital role, blood levels of calcium are kept within closely defined limits. Diets high in wheat bran and cereals are high in phosphorus and low in calcium which may cause calcium deficiency. A lack of calcium and phosphorus in the diet of growing foals delays the closure of the epiphyseal plates of the long bones and is associated with developmental orthopaedic disease (DOD). In adult horses it causes lameness and bone fractures. If there is so little Ca and P in the diet that the bone fails to mineralise correctly, the condition is known as rickets in growing horses and osteomalacia in adult horses. In severe cases the bone becomes demineralised and fibrous tissue is deposited in its place, leading to enlargement of the facial bones called 'big head'. Horses working hard in hot conditions may lose large amounts of calcium in sweat leading to post-exertional hypocalcaemia; horses show muscle spasms, inco-ordination and synchronous diaphragmatic flutter.

< previous page

page_147

next page >

< previous page

page_148

next page > Page 148

Horses require a daily intake of 5 g Ca and 2 g P per 100 kg body-weight to balance daily losses and the efficiency of absorption from the gut. This approximates to 2.5 g Ca per kg diet and 1 g P per kg diet. The availability of calcium in feeds lies between 45 and 70%, and the amount of phosphorus will affect absorption from the gut. Thus the mature adult horse will require about 23 g calcium and 18 g phosphorus in the diet, met by 64 g of limestone or 60 g dicalcium phosphate. Limestone flour is a preferred source of calcium to bonemeal due to recent concerns over BSE. Iron Many horse-owners use iron supplements in the mistaken belief that this will increase the horse's red blood cell count. Nutritionists and vets have questioned the benefits for a few years now. Iron is required for the formation of haemoglobin, the oxygen-carrying molecule. In practice, iron-deficient diets are rare and true iron deficiency anaemia is usually a result of blood loss either externally (wounds) or internally (EIPH, parasitism or gastric ulcers). There is no benefit to supplementing the healthy performance horse with iron. A horse in heavy work would need approximately 1000 mg of iron per day. Copper This is an essential mineral. Copper-dependent enzymes are required for mobilisation of iron stores, production of elastic tissue and the preservation of mitochondria (the powerhouse of cells). Copper levels in herbage are particularly low in parts of the U.K. and Ireland, and copper is widely supplemented to cattle in these areas. High levels of iron, sulphur and molybdenum will also reduce copper availability to the horse. The horse in hard work will need approximately 190 mg copper per day. Zinc Zinc is required as a cofactor in many enzyme systems; however, it is rarely deficient. Manganese Manganese is required for bone formation and the energy production process in the mitochondria. It is also involved in the production of

< previous page

page_148

next page >

< previous page

page_149

next page > Page 149

fatty acids and amino acid metabolism through enzymes or enzyme activators. Horses in hard work will require approximately 500 mg per day. Iodine. Iodine is part of the hormones thyroxine and triiodothyronine, both of which are produced by the thyroid gland. In the performance horse, thyroxine plays a vital role in controlling the metabolic rate and energy metabolism in the cell. A deficiency or toxicity of iodine may result in goitre. The horse in hard work requires approximately 2.75 mg iodine per day. Cobalt This is a component of vitamin B12. See Vitamin B complex below. Chromium Chromium is essential for normal carbohydrate metabolism, as it is a component of glucose tolerance factor (GTF). Chromium is found in insulin-sensitive tissue where it reduces insulin resistance and stimulates glucose clearance and amino acid synthesis. It is thought that chromium supplementation in the form of chromium yeast (5 mg/day) is beneficial to horses in hard work, although most evidence is as yet anecdotal. Selenium During exercise, toxic substances are produced within the horse's cells and these are known as free radicals. These may then attack and break down cellular structures. Both selenium and vitamin E help to 'mop up' these toxic substances before they do any damage. However if the horse's selenium status is low this will reduce the antioxidant capacity and lead to damage, particularly of the muscle and respiratory cells. There are areas of the U.K. and Ireland which are low in selenium. However, supplementation should be carried out with advice from a nutritionist or vet, as the requirement and toxicity levels are relatively close. Recent research indicates that the source of selenium may be important and seleno-yeast may be more beneficial than the traditionally used sodium selenite.

< previous page

page_149

next page >

< previous page

page_150

next page > Page 150

Vitamins Vitamins can be split into two groups, fat soluble and water soluble. Vitamins are required in small quantities but are absolutely vital to the health of the horse. Fat soluble: vitamins A, D, E and K Water soluble: B-complex vitamins and vitamin C (ascorbic acid). Fat soluble vitamins may be stored in fat in large amounts and this may cause toxicity problems if supplementation is over-zealous. Water soluble vitamins are not soluble in fat and therefore are not stored in any great quantities in the horse's body. Daily production of these vitamins by the horse is required. Vitamin C can be made in the body by the horse and the micro-organisms can make vitamin B complex in the hindgut. Horses on high grain diets or those that have a compromised gut flora due to stress or antibiotic therapy will require supplementation. Vitamin A Carotenes are the natural source of vitamin A and are found in abundance in green herbage. However, hay contains little if any carotene (loses its green colour) and so horses kept on hay in the winter with no access to green forage may deplete their vitamin A stores within 2 months of being stabled. (Good, early cut alfalfa hay may be the exception to this rule.) High levels of vitamin A are thought to increase fertility, but there has been little scientific evidence to date. Horses in hard work will require approximately 50,000 IU/day of vitamin A. Vitamin D Vitamin D is a hormone and horses are able to make it in their skin when exposed to sunlight. Vitamin D is therefore not required in the diet if sufficient amounts of sunlight are available. Horses who are rugged up when out will require vitamin D as will stabled horses. Vitamin D is required for absorption of calcium and phosphorus from the horse's gut: if it is deficient neither of these minerals will be absorbed properly and this may, in turn, lead to further problems. Although cod liver oil is a good source of vitamin D, it may put

< previous page

page_150

next page >

< previous page

page_151

next page > Page 151

fussy feeders off their food and this can be a real problem in very fit horses who need to be eating to appetite. Horses require approximately 5000 IU/day of vitamin D. Vitamin E As discussed earlier, vitamin E is an antioxidant, preventing cell membranes from undergoing oxidative damage. Vitamin E tends to be supplemented with selenium since their roles are closely related. Vitamin E and selenium are often used together in cases of exertional myopathy because of their antioxidant properties. Horses in work require higher levels of vitamin E due to the increased workload of body cells, particularly the muscles. Working horses require approximately 1000 IU/day of vitamin E. Vitamin K The major function of vitamin K is in the blood-clotting process. It is sometimes supplemented in the diets of horses that regularly have nosebleeds. A deficiency is rare, but 20 mg vitamin K per day can be safely given to working horses. Vitamin B Complex. B vitamins (thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, B12, and folic acid) are found in fresh herbage and protein-rich foods. They are mostly involved with carbohydrate metabolism. Vitamin B12 is essential for protein metabolism and hence growth and reproduction. Cobalt is required in the diet for the microbial synthesis of vitamin B12 and should be supplied at a minimum rate of 0.1 mg/kg diet. Thiamine is said to have a calming effect and also acts as an appetite stimulant. A deficiency of folic acid may cause nutritional anaemia, as it is required in the synthesis of red blood cells. Biotin has received much interest due to its requirement in the production of quality hoof horn. The horse may need up to 20 mg biotin per day; however, this should be fed with other nutrients required for hoof horn synthesis such as calcium, methionine and zinc. General supplementation of vitamin B complex may therefore assist in cases of poor appetite; certain types of anaemia (especially post-viral), compromised gut flora population and liver dysfunction.

< previous page

page_151

next page >

< previous page

page_152

next page > Page 152

Vitamin C Vitamin C (ascorbic acid) is made in the liver from glucose. Vitamin C is an antioxidant and is often fed to horses to help them withstand stress. Vitamin C also enhances the formation of bone, and aids in the utilisation of folic acid, vitamin B12, and glucose. It is required for the synthesis of collagen which is very important for the performance horse. It has been suggested that times when vitamin C supplementation may be beneficial are during growth, peak performance, when the horse is stressed, or when the horse is severely ill and losing weight. This may reduce the amount of glucose available for vitamin C production. What to Feed the Performance Horse The task of the digestive system is to convert nutrients into end-products which can be absorbed across the gut wall. These end-products pass into the bloodstream and are used by the body, firstly to stay alive, a process known as 'maintenance', and secondly for 'production', which includes any function over and above maintenance, e.g. pregnancy, lactation, galloping and jumping, or simply growth. If the horse-owner is to feed their horse so that it can perform the work being asked of it, they must be able to match the nutrient requirements with what is actually contained in the foods available. Types of Feed and Their Nutrient Value Feeds can be analysed to indicate the nutrients they contain, and a basic knowledge of the composition of various feeds is essential when preparing a feed ration for a horse. Every horse-owner is aware that oats and beans are more 'heating' than barley, but this superficial knowledge is not adequate and tables showing feed values should be used. The types of feed given to horses fall into five main categories: (1) Cereals. The energy-giving basis of the concentrate ration, e.g. oats, barley and maize. (2) Protein feeds. These can be of animal origin (e.g. dried milk) or of plant origin (e.g. linseed, soya and other beans and peas). (3) Intermediate feeds. These include wheatbran, sugarbeet pulp and grass meal. (4) Forages. Grass, hay, haylage and silage. (5) Compound feeds. Nuts and coarse mixes.

< previous page

page_152

next page >

< previous page

page_153

next page > Page 153

These feeds will now be considered in more detail, and reference can be made to the table of nutritive values (Table 13.1). Cereals Oats Oats have a high energy value due to their starch content, and are the traditional grain fed to working horses in this country and northern Europe. If, and only if, they are of good quality can oats provide enough protein for the horse in hard work. The grain should be plump, with more kernel in relation to husk, shiny and dust-free, and a pale yellow colour with a sweet smell. Black oats are also available, but are becoming increasingly uncommon. Oats are fed bruised; the husk should be broken without damaging the kernel. Once bruised, they should be used within 3 weeks as the nutritive value gradually deteriorates. Oats can make up all the concentrate ration, but it must be remembered that they are low in the amino acids lysine and methionine, with a poor calcium to phosphorus ratio. Naked oats are a modern development of this traditional feed; the hull separates from the kernel during harvesting to leave a clean grain. Naked oats are more dense and have higher energy and protein levels than conventional oats. Fewer oats need to be fed to supply the same levels of energy in the diet and there is no need to crimp or roll naked oats. Naked oats are intended as a feed for performance horses; they can contain up to 27% more energy than conventional oats. Great care must be taken when feeding them they must be fed in smaller quantities and the forage level of the diet must be kept up. Barley Barley has a higher energy content than oats (hence its fattening properties) but a lower fibre content. The grain should be full, clean and shiny, with a rounder, plumper appearance than oats. There should be no sharp awns amongst the grains. Barley can be fed rolled or boiled or heat-treated (micronised, steamed, or extruded). These treatments all increase digestibility and palatability. Rolled barley can be crumbly and dusty, and the micronised form, although more expensive, is becoming increasingly popular and is included at high levels in some coarse mixes.

< previous page

page_153

next page >

< previous page

next page >

page_154

Page 154 Table 13.1 Nutrient values of commonly fed concentrate feeds.

Oats Naked oats

Crude protein (%)

DCPa

Oil

(%)

(%)

MAD fibreb (%)

9.6

78

4.5

17

13.5

Ca

P

Lysine

DEc

(g/kg)

(g/kg)

(g/kg)

(MJ/kg)

0.7

3.0

3.2

1112

9.7

3.2

0.2

0.4

5

16

Barley

9.5

78

1.8

7

0.6

3.3

3.1

13

Maize

8.5

78

3.8

3

0.2

3.0

2.6

14

7.6

2.4

5.2

7.7

18.5

2.4

6.3

26

13.3

0.7

4.0

15.8

14

Linseed

22

17

Extracted soyabean meal

44

39

1.0

Peas

23

19

5

Grassmeal

16

11

3.2

36

6.0

2.3

8

9.6

Alfalfa meal

17

12

3

40

15.0

2.0

8.2

9

Wheatbran

15.5

1012

3

12

1.0

1.0

34

100 0

Sugarbeet pulp

7

5

Vegetable oil

9

0

Molasses

3

12

32

10 8.2

12

6

11

10

11

2.8

10.5

0

0

0

0

35

0

7.2

1.0

0

11

a Digestible crude protein. b Modified acid detergent fibre. c Digestible energy.

< previous page

page_154

next page >

< previous page

page_155

next page > Page 155

Barley seems less likely to make horses overexcited or 'gassy' than oats, but this property is hard to explain scientifically. Like oats, barley has a poor calcium to phosphorus ratio and is low in essential amino acids. Maize Maize has a high energy content and contains little fibre; it is rarely included at more than 25% of the concentrate ration. It appears to be quite 'heating', and too much maize may produce lumps under the skin. Maize is generally fed micronised or flaked, and should be bright golden in colour, crisp and clean. The 'Heating' Effect of Gain Grain is often said to be 'heating', meaning that it results in a horse being overexcited and difficult to control. This 'heating' effect stems from two sources: Overfeeding energy. Many 'hot' horses are simply getting too much energy for the job that they are doing and a reduction in the concentrate ration and an increase in the roughage will solve many problems. The behavioural problems are made worse by confining the horse to its stable 23 hours a day and then working the horse to increase its fitness a veritable time bomb. Fermentation. Any grain passing through into the large intestine is rapidly fermented by the intestinal microorganisms; there is an increase in the acidity of the caecum which may lead to discomfort, and the products of digestion pass very quickly into the bloodstream. There is a rise in blood levels of glucose and volatile fatty acids which stimulates the metabolic rate, thus 'heating' the horse both literally and mentally. Processing cereals increases the amount of digestion in the small intestine, reduces caecal fermentation and keeps the horse's metabolism more stable. Protein Feeds. Beans and Peas These can be fed crushed, split or micronised. Peas and locust beans, which are brown and sweet-tasting, are frequently found in coarse

< previous page

page_155

next page >

< previous page

page_156

next page > Page 156

mixes. Not only do they have an energy content equivalent to that of oats, but they also have a high protein value. They are suitable for horses in hard work or out-wintered stock, but they appear to be very 'heating' and should be fed with discretion. Linseed Linseed is the seed of the flax plant and is high in protein and fat, hence its high energy content, although its protein quality is not high. The seed should be small, flat, shiny and dark brown, and it has to be carefully prepared: the linseed should be soaked overnight (for at least 6 hours) and then brought to the boil and simmered for at least 1 hour, or until the seeds have ruptured and the liquid is thick and jelly-like. This liquid can be added to the feed cold or hot. Linseed can now be cooked conveniently in microwave ovens, thus overcoming cooking problems. The beneficial effects seen in coat condition are due to the high oil content of linseed. Similar effects will occur by feeding a good vegetable oil. Soyabean Meal Oilseed meals like soyabean meal are much richer sources of protein than cereals, and the balance of amino acids is superior. Soyabean meal is considered to be the best quality vegetable protein fed to horses. Raw soyabeans are poisonous, but if reliably cooked the meal can be used as the sole source of supplementary protein in the horse's ration. Soyabean meal contains 4449% protein; more expensive soya flakes are also available, containing 3640% crude protein. Feeding 1 kg of 40% soyabean meal can raise the protein content of an oats-and-hay diet from 8 to 12%, which would then provide adequate protein for a broodmare in mid-lactation. Intermediate Feeds Bran Bran is fed as a filler and as a binder for feed, or as a palatable mash. The energy content is low; thus bran is not 'heating'. Although the protein content is high, it is of poor quality. Bran is the inner husk of the wheat grain and should ideally consist

< previous page

page_156

next page >

< previous page

page_157

next page > Page 157

of broad, pinkish sweet-smelling flakes. Good bran is hard to come by, and rather than feed expensive, poor quality bran it is better to use hay chaff or sugarbeet pulp to bulk out feeds. It was thought feeding bran had a mild laxative effect, research has failed to support this. Oats are also higher in fibre than bran! So if bran is not a laxative, does not contain high levels of fibre and does not increase faecal water content, the purpose of feeding it becomes questionable. Bran also affects calcium uptake, and a calcium supplement should be fed when bran is used. Bran mashes cause upset to the horse's diet when fed infrequently i.e. once per week which is traditionally done! This upsets hindgut microbes and should be avoided. Sugarbeet Pulp Dried sugarbeet pulp is a very under-estimated and under-utilised horse feed. Produced as either shreds or pellets, it is the dried remainder of the sugarbeet once the sugar has been extracted. Once soaked, it makes a palatable and nutritious succulent for all types of horse and pony. Sugarbeet pulp is economical and with a protein content of 7% and an energy value similar to oats, it has the potential to be a significant part of the horse's ration. Instead it tends to be used as a feed-dampener, with horses rarely receiving more than a double handful in each feed. The high fibre content of beet pulp (34%) means that it is a compromise between a forage and a concentrate. The sugar is digested easily in the small intestine giving 'instant energy', while the fibrous part is fermented in the hindgut, releasing nutrients more slowly. This makes it a good feed for endurance horses and hunters, which may go many hours between feeds. Very wet beet pulp is a useful way of encouraging the horse to rehydrate himself. Sugarbeet pulp should be soaked before feeding to prevent it swelling in the oesophagus, stomach or small intestine and causing problems. Shreds should be soaked overnight for use the following day, while pellets should ideally be soaked for 24 hours. Fresh beet pulp should be soaked every day as it can go off rapidly in warm weather. Shreds should be just covered with water so that a wet, firm feed results, not a sloppy mass. One kilogram of pellets should be soaked in 2 kg water. Horses can be fed up to 1.8 kg (4 lb) dry weight of beet pulp per day; this amounts to about four scoops of wet sugarbeet pulp and would replace 1.8 kg (4 lb) hay. Sugarbeet pulp is also a useful source of

< previous page

page_157

next page >

< previous page

page_158

next page > Page 158

calcium. Unmolassed sugarbeet pulp is now available, reducing the soluble carbohydrate level of the diet. Forages The horse's natural food is grass. Grass can be conserved for winter feeding in several ways hay, silage and haylage, are all used to provide bulk in the horse's ration. Bulk should make up at least 50% of the horse's total food intake, an absolute minimum being 0.7 kg per 100 kg body weight, i.e. 3.5 kg (8 lb) hay per day for a 500 kg horse. For a horse in light work, bulk would probably make up over 75% of the ration. Conserved grass can only be as good as the original grass minus conservation losses; so when assessing such food consider the crop from which it came, then consider how well it has been conserved. Hay The quality of hay feed can make or break a diet. Good hay should be greenish, smell sweet, and be dust- and mouldfree. (Barn-dried hay has less smell; it also has a higher energy and protein content.) Dusty hay can damage a horse's wind, and should be thoroughly damped if there is no alternative to feeding it. Mouldy hay should never be fed. Since 80% of the nutrients of grass are in the leaf, stemmy hay offers a lower feed value; it is also less digestible. Hay should be cut when the grass is in flower, but is often cut later than this to gain a heavier yield. If it is cut too late, the seed heads ripen and are shed; thus the feed value of the grass, and hence the hay, falls. This can lead to the incongruous situation where early-cut hay, even if not very well made, can be of better feed value than late-cut more attractive-looking hay. Buying good-quality hay, although it is expensive initially, pays off in the long run, with horses requiring fewer concentrates and staying healthier. As can be seen from Table 13.2 while the energy content of good- and bad-quality hay varies little, the protein content can vary dramatically. This can be very important for horses in hard work, and the concentrate ration will have to make up this shortfall. There are three common types of hay. Meadow hay is made from permanent pasture containing vetches and herbs, and is usually soft hay with a low protein content. Seed hay is made from rye-grass-based leys, giving a coarser,

< previous page

page_158

next page >

< previous page

next page >

page_159

Page 159 Table 13.2 Composition of hay and other high fibre feeds. Feed

Hay Silage

Crude protein

Crude fibre (%)

Digestible energy (MJ DE/kg)

Dry matter (%)

4.510

3040

710

80

10

30

10

25

Haylage

814

3038

911.5

5565

Straw

3

40

6

88

Sugarbeet pulp

7

34

10.5

Fed soaked

Alfalfa chaff

1516

32

910

80

Alfalfa/straw chaff

10.5

38

7

80

9

20

8.5

85

16

36

910

85

High fibre cubes Grassmeal

pH

5.35.8

harder hay with higher protein values. (A ley is grass sown as a crop and left down for from 1 to 8 years.) Due to the coarser grass types, seeds hay needs a long spell of good weather to be made well. Otherwise it has to be conditioned, or lacerated by machine, to enable it to dry more quickly, but if it is rained on after this, much of the nutritive value is washed out of the hay. Lucerne (alfalfa) is a legume grown in small quantities in the east of England. Due to the price and high protein value, its main use is to supplement grass-hay ration. Good lucerne hay is usually barn dried. Sainfoin hay is similar but less common. Silage. Silage, if well-made, is virtually dust- and fungal spore-free; however, feeding silage is often not a practical proposition for horse-owners for two reasons: Silage is made in silos, clamps or big bales; these methods pose considerable logistical problems how do you get the silage to the horse? The packaging and storage of silage are vital; if done incorrectly potentially lethal micro-organisms can develop. Ensiling a crop involves 'pickling' it in its own juice. The crop (usually grass or maize in the U.K.) is cut and left to partially dry or 'wilt' in the field, until the moisture content has dropped to 6075%. Grass is usually cut at or just after heading: in other words, the seed heads have appeared but the grass has not flowered. As many as four

< previous page

page_159

next page >

< previous page

page_160

next page > Page 160

cuts may be taken from one field in one growing season if the grass is intensively grown; individual cuts are smaller but the total tonnage is greater. The crop is then put into a silo, clamp or bag. Clamp silage is gathered from the field by a forage harvester that chops the grass so that when it is consolidated into a clamp, as much air as possible can be excluded. The clamp is covered and kept air-tight. The soluble sugars in the grass undergo fermentation, resulting in the production of acetic acid (vinegar) and an increase in acidity or lower pH. The acidity prevents the growth of harmful bacteria and fungal spores, and preserves the grass. The dry matter content of the grass needs to be at least 25% for this fermentation to drop the pH sufficiently; if the dry matter is only 15% the pH will only fall to about 4.5, bacteria will grow and the silage will undergo a secondary fermentation resulting in a poor quality product that is not palatable to horses. Molasses and other additives are sometimes added to clamp silage to ensure that the correct fermentation takes place. Big bale silage has a higher dry matter, often being wilted in the field to 40% dry matter. It is then tightly baled and wrapped in plastic, or put in a tough plastic bag. A mild fermentation takes place resulting in a pH of 56. Additives are not used and it is the airtight environment and low water activity that preserves the grass and prevents bacterial proliferation. If silage is readily available, remember the following points: The silage should have been made to meet the nutrient demands of horses; silage made for beef and dairy cows tends to be too rich for horses. The acidity of the silage must be carefully monitored to check that a stable fermentation has taken place; the pH should be between 5 and 6 in big bale silage and 44.5 in clamp silage. The grass from which the silage has been made should be free of weeds, not cut too close to the ground, and there should be no mole hills in the field. There must not be any mould. The dry matter should be a minimum of 25%. The silage should have an attractive vinegary smell and must not smell of ammonia. If these criteria are met then good quality silage can be a useful hay substitute, but always remember that there have been several deaths in the U.K. among horses eating big bale silage. These deaths were

< previous page

page_160

next page >

< previous page

page_161

next page > Page 161

associated with toxins and bacteria that had proliferated due to abnormal fermentation in the silage. Hay Alternatives The British climate is not ideally suited to making hay, and as a result horse-owners may be faced with a shortage of good quality hay. The horse is designed to live on a high fibre diet; any shortfall of hay must be compensated for by adding another high fibre feed, for example: silage haylage straw chaffs sugarbeet pulp high fibre cubes succulents, e.g. carrots. Most of the hay alternatives mentioned have a better nutrient value than the hay they are replacing or supplementing and should be fed carefully; it may be necessary to reduce or change the concentrate ration. If hay is replaced by a more concentrated energy source, such as haylage, the horse will eat its day's ration of feed more quickly and may become bored. All new feeds, including hay alternative such as haylage, straw and silage, should be introduced gradually into the horse's ration to avoid digestive upset. Haylage Haylage lies between silage and hay in its feeding value and digestibility. It is highly palatable and horses can take in large amounts of energy quite rapidly, so care should be taken not to overfeed. Haylage should be substituted for hay on a weight for weight basis; it contains a lot of water and is consequently heavy, so that the horse will be receiving equivalent amounts of energy and protein from a smaller volume ration. The downside of this is that the horse will be receiving less fibre and the haylage will be eaten more quickly than the equivalent hay ration. Correct fermentation is vital to preserve the haylage and also affects its suitability for feeding to horses. The following guidelines should be used:

< previous page

page_161

next page >

< previous page

page_162

next page > Page 162

The dry matter should be between 45 and 65% and preferably 5565%; however, forage with a dry matter of only 45% can be considered if all the other parameters are satisfactory. The pH (acidity) should lie between 4.5 and 5.8. Silage or haylage with a pH of less than 4.5 is often unpalatable and may cause scouring; it can also be fatal to donkeys. Above a pH of 6 the silage or haylage will not be acidic enough to prevent the potentially lethal micro-organisms developing. The ammonia nitrogen level should be less than 5%. Some haylage is also produced specifically for horses. Grass is cut and allowed to wilt until the moisture content is down to about 45% and then baled in the same way as hay. The bales are then compressed to about half their size and sealed in tough, plastic bags. Fermentation takes place which preserves the grass. Different types of bagged haylage are produced; for example, alfalfa and high fibre types are available. Special closely woven haynets can be used to feed haylage, in order to slow down the horse's rate of eating. Straw Good quality spring barley or wheat straw in small quantities can act as a useful source of fibre for horses with sound teeth, but it is deficient in most nutrients. Fungal spores tend to be concentrated on the leafy part of plants. Straw has little leaf, and it is easier to get clean straw than it is hay, which makes straw useful to feed as bulk to accompany a haylage or silage based ration. It is also a good filler for fat ponies that do too well on hay. Care must be taken to provide correct levels of minerals and vitamins if straw is to be used in the diet. Hydroponic Grass Hydroponic grass is the result of germinating barley seeds in lighted trays in a controlled humid environment in a specially designed cabinet (Figs 13.4, 13.5). The 'grass' is harvested when about 6 days old, and fed as a succulent feed with a feeding value similar to that of spring grass in terms of energy and protein. The grass is dust-free and highly digestible with good levels of vitamin E, beta-carotene and biotin. About 75% of the grass is water, resulting in a digestible energy of about 2.5 MJ/kg half that of hay or haylage, despite its high digestibility. The initial cost of the equipment and the labour needed

< previous page

page_162

next page >

< previous page

page_163

next page > Page 163

Fig. 13.4 A small hydroponic unit. to produce the grass make hydroponic grass expensive, but the cost may be justified in some circumstances, e.g. stud farms with early foaling mares. Chaff Traditionally a horse's concentrate feed was bulked up with chopped hay and/or straw to stop the horse bolting its feed and to encourage it to chew the feed more thoroughly. The modern equivalent takes the form of molassed chaff, and as the popularity of bran has waned, so the use of chaff has increased. Molassed chaff is particularly useful for horses and ponies on a very small concentrate ration. It prevents them from bolting the feed, provides fibre and soaks up any supple-

< previous page

page_163

next page >

< previous page

page_164

next page > Page 164

Fig. 13.5 Hydroponic grass being fed. ments the horse may be receiving. Fed with a horse and pony cube, it makes a simple ration that can be fed safely by the most inexperienced feeder. Most straw-based, molassed chaffs are designed to bulk out the hard feed and to slow down the horse's rate of eating. Hay and alfalfa or straw chaffs have been designed as partial or complete hay replacers, to be fed weight for weight for good quality hay. Alfalfa chaff is too high in energy and protein to be fed to most horses as a hay replacer, but is a useful 'top-up', especially for horses in hard work. Compound Feeds Compound feeds are complete balanced diets formulated by nutritionists. They contain a mixture of commonly used ingredients: Cereals: oats, barley, maize, wheatfeed, oat feed Forage products: grassmeal, alfalfa chaff or pellets, herbs Protein sources: full fat soya, sunflower meal, fishmeal, peas, beans

< previous page

page_164

next page >

< previous page

next page >

page_165

Page 165 Other: rice bran, vegetable fat, linseed cake, bread meal, molasses, salt, dicalcium phosphate, limestone flour, vitamin premix as pellets or powder. Compound feeds usually consist of a pellet/cube, or a coarse mix. Pellets are manufactured by grinding down the ingredients to a powder, mixing this with a binding agent such as molasses and/or oil and then pushing through a dye. Feeding pellets has several advantages, including economy of labour, convenience of feeding, and knowing that a balanced ration of known quality is being fed. Coarse mixes generally contain a mixture of micronised cereal products, peas, beans, vitamin and mineral pellets which are then mixed together with molasses or syrup. These mixes are usually very palatable to the horse and attractive to the owner which is equally important! Coarse mixes are designed to be fed with hay alone, and it is pointless to mix cereals with them. Frequently, horses will select ingredients from a coarse mix. They will often leave the vitamin/mineral concentrate pellet as sometimes it is the least palatable ingredient. This may cause problems when horses are in hard work and they need to eat up all their feed. If horses keep on leaving 'bits' then a cube should be fed instead. Compound feeds contain a mixture of ingredients intended to form a balanced ration for a particular purpose. They range from low energy type feeds such as horse and pony nuts or mixes to high energy performance feeds. More specialised rations are now available, such as high fat rations for horses in hard work (see Table 13.3). Compound feeds cannot be correctly balanced for every horse all of Table 13.3 Typical nutrient values of compound feeds. Crude oil (%)

Crude fibre (%)

Crude protein (%)

Total lysine (%)

Digestible energy (MJ/kg)

Total ash (%)

Horse and pony cubes

3

1415

10

0.45

9

910

Performance cubes

3.54

8.5

1213

0.55

12

810

Stud cubes

3

910

1315

0.65

11

810

Creep feed

44.5

6.57.5

1718

0.9

13

79

Yearling cubes

33.5

1516

0.75

11

79

Balancer

3

< previous page

8.5 10

1719

page_165

1518

next page >

< previous page

page_166

next page > Page 166

the time. A horse may require more energy than is provided by horse and pony cubes, and yet may hot up on racehorse cubes. Of the many different types of compound feed available, one or more may suit a particular horse. It must always be remembered that horses have individual preferences, and the palatability of feeds must be taken into consideration. There are several national feed manufacturers supplying commercial feeds for horses, as well as many local feed mills. There is a wide variation in nutritional content of these feeds. Some contain specially formulated premixes, designed to balance the ingredients used and to match the requirements of the intended end-user. Others contain cheaper ingredients and premixes are purchased 'off the shelf' and these do not necessarily balance the ingredients within the mix. Some feed manufacturers formulate feeds on a least-cost formulation. This results in regular changes to the ingredients which may be detrimental to the health of horses. Feed manufacturers must, by law, declare levels of certain nutrients on labels on each feed bag. These are protein, fibre, oil, ash, vitamins A, D and E and copper. Some feed manufacturers now declare energy levels, but this is not a legal requirement. Ingredients must also be listed in descending order of their amount in the feed which allows the horse-owner to assess the quality of the feed. The majority of cereals used in compound feeds have been processed by one of a number of methods. rolling micronising extrusion boiling/steaming. The aim of 'cooking' ingredients is to increase digestibility of the feed. The rules of feeding, the nutrient requirements of horses, and the nutrient content of feedstuffs can be brought together to plan simple rations for horses competing and working at different levels. The Theory of Rationing A 'ration' is an allocation of chosen foodstuffs sufficient to provide the daily nutrient requirements of a particular horse. It can be calculated very easily by any horse-owner provided they follow a few simple rules and have access to a table giving the nutritive value of the feedstuffs available.

< previous page

page_166

next page >

< previous page

page_167

next page > Page 167

Horses are fed for two main reasons: firstly to keep them alive, and secondly so that they can perform the tasks we ask of them. In scientific terms, we call this 'maintenance' and 'production'. Maintenance Feeding a horse for maintenance is giving it enough food to maintain it in its present state. This means providing energy for the muscles of the gut, heart and lungs so that essential processes can take place, energy for grazing, for maintaining body temperature and for replacing cells to keep the body in good working order. The hunter turned away during the summer is being fed for maintenance and survives happily on grass alone, although a source of minerals may be required in some areas. The maintenance requirements of a horse can usually be provided for by forage alone. The major factor which determines how much energy a horse needs for maintenance is its bodyweight bigger horses need more food just to stay alive. Production. Production may be divided into six different forms: growth, pregnancy, lactation, fattening, work and repair (or recovery from illness and injury). In this book we are concerned with work, which will fall into various categories depending on the age and ability of horse and rider. The extra energy and protein required by the horse for work are usually provided by concentrates. The competition horse would not be able to extract enough energy or protein from a forage ration to perform the work without losing condition. The energy content of a foodstuff is measured in megajoules (MJ). Thus the energy content of oats is 1112 MJ/kg i.e. each kilogram contains 1112 megajoules of digestible energy (DE) (see Table 13.1). Megajoules are merely metric calories; all we are doing is 'calorie-counting' for our horse. Protein is measured as a percentage. Oats contain 9.6% crude protein, each kilogram (1000 g) of oats containing 96 g (11%) of crude protein (see Table 13.1). The Rules of Rationing There are eight steps involved in ration calculation and adjustment to

< previous page

page_167

next page >

< previous page

next page >

page_168

Page 168 suit individual horses. Each step will be explained and a ration actually calculated afterwards. Step One: Estimation of Bodyweight Several methods are available: table of weights (see Table 13.4) calculation weightape weighbridge. Table 13.4 Approximate bodyweights. Type

Height (cm)

Pony Pony Pony Foal/weanling Pony or yearling Pony Cob Hack Hunter Hunter Hunter Shire

Weight (hh)

(kg)

(lb)

101

10

200

440

127

12.2

300

660

132

13

350

770

132

13

200

440

142

14

400

880

147

14.2

450

990

147

14.2

500

1100

152

15

450

990

162

16

550

1210

162

16

600

1320

168

16.2

650

1430

173 +

17 +

1000

2200

Calculation Few of us have access to an equine weighbridge so an equation was devised relating the horse's heart girth and the length from the point of shoulder to the point of the pelvis to the bodyweight (Fig. 13.6).

or

< previous page

page_168

next page >

< previous page

page_169

next page > Page 169

Fig. 13.6 Measurement of girth and length. For example, a 162 cm (16 hands) middleweight horse which has a girth measurement of 165 cm (65 inches) and a length of 173 cm (73 inches).

or

Weightape It is possible to buy a weightape which uses a measurement of the horse's heart girth to give an approximate bodyweight. Whilst not very accurate, this method is quick and easy to use and will help you record any changes in your horse's condition if measured on a regular basis. Weighbridge This is the only accurate way of assessing a horse's weight. A nearby racing yard may have a weighbridge which they will let you use. Otherwise take your horse to the nearest public weighbridge

< previous page

page_169

next page >

< previous page

next page >

page_170

Page 170 and take an old carpet, too, as horses do not like walking on sheet metal. Step Two: The Horse's Appetite It is futile to place more food in front of the horse than it is physically capable of eating: the ration must be within the appetite of the horse. Appetite is governed by bodyweight (Table 13.5):

Table 13.5 The relationship between height, girth, bodyweight and appetite. Height

Girth

Bodyweight

Appetite

(cm)

(hh)

(cm)

(kg)

(kg dry matter)

111

11

135145

200260

4.56

122

12

140150

230290

57

132

13

150160

290350

6.58

142

14

160170

350420

89.5

152

15

170185

420520

1012.5

162

16

185195

500600

1214

173

17

195210

600725

1318

NB: The values in this table are averages and only approximate. Step Three: Calculating the Energy for Maintenance The horse requires a minimum amount of energy a day just to stay alive: this is related to the bodyweight of the horse bigger horses need more feed than smaller ones (see Table 13.5).

A 500 kg horse will require 68 MJ DE per day to stay alive and to maintain its bodyweight constant.

< previous page

page_170

next page >

< previous page

next page >

page_171

Page 171 Step Four: Calculating the Energy for Work The amount of energy the horse needs to carry out the work we demand of it depends on the intensity and duration of the work and the horse's bodyweight. The variation in trainer or rider's perception of how much work the horse does has been minimised by giving the work a 'work score' from 1 to 8. Example types of work have been outlined: these are not rigid and you should fit in your horse's individual workload. For each 50 kg of bodyweight, add the following work score (Table 13.6) to calculate the horse's energy requirement for work. Table 13.6 Work scoring. Type of work

Work score (MJ DE)

Extra energy needed per day by a 500 kg horse MJ DE/day

One hour walking

+1

10

One hour walking including some trotting

+2

20

One hour including trotting and cantering

+3

30

Schooling, dressage and/or jumping

+4

40

Novice ODE or hunting 1 day a week

+5

50

Intermediate ODE, hunting 3 days a fortnight, Novice 3-day event

+6

60

Advanced ODE, Advanced/intermediate 3-day events, hunting 2 days a week

+7

70

Racing

+8

80

A 500 kg Novice one-day event horse will have a score of 5; the extra energy needed to carry out that work will be:

< previous page

page_171

next page >

< previous page

next page >

page_172

Page 172

The energy requirement for work is then added to the maintenance requirement to give the total daily energy requirement per day.

Maintenance requirement for 500 kg horse

=

68 MJ DE/day

Work requirment for 500 kg Novice eventer

=

50 MJ DE/day

Total energy requirment

=

118 MJ DE/day

Step Five: The Forage to Concentrate Ratio. The horse's work level will determine the amount of energy to come from the forage part of the ration and the amount to come from the concentrate part. Using the revised table of forage to concentrate ratios (Table 13.7) we can calculate how the energy is going to be partitioned. Table 13.7 Forage to concentrate energy partition. Energy % Work score Maintenance Resting 12 Light 35 Medium 67 Hard 8 Fast

From hay 100

From concentrates 0

75

25

60

40

50

50

50

50

Of the total energy requirement (118 MJ DE/day) for our eventer in medium work (work score 5), 60% will come from hay and 40% will come from concentrates.

71 MJ DE per day are to be supplied by hay and 47 MJ DE per day by concentrates.

< previous page

page_172

next page >

< previous page

next page >

page_173

Page 173 Step Six: Making the Ration The next step is to convert these figures into a sensible ration. Using the table of nutrient values (Table 13.8) the energy value of food will be matched with the energy requirements of the feeds. Table 13.8 Nutrient values of common feeds. Crude protein (%)

Digestible energy (MJ/kg)

4.58

78

Hay Average Good Poor Haylage

910

9

3.56

7

3.56

7

Concentrates Oats Barley Maize Extracted soyabean meal Peas Wheatbran Sugar beet pulp Vegetable oil

10

1112

9.5

13

8.5

14

44

13.3

23

14

15.5

11

7

10.5

0

35

10

9

13

12

15

11

Cubes Horse and Pony Performance Stud

The 500 kg event horse is to receive 71 MJ DE per day from average quality hay containing 8 MJ DE per kg.

The horse is to receive the remaining 47 MJ DE as concentrates. This can be done by feeding a performance horse cube with an energy content of 13 MJ DE/kg.

< previous page

page_173

next page >

< previous page

next page >

page_174

Page 174

Although perfectly adequate, this is a rather simplistic ration and a mix of feeds is much more likely to be fed (Table 13.9). Table 13.9 The final ration. Feed

Quantity (kg)

Oats Sugarbeet pulp (dry weight) Performance cubes

(lb)

2

4.4

0.5 1

Energy provided (MJ DE)

1 2.2

Total

24 5 13 42.0

Along with his 9 kg (20 lb) of hay, our event horse is going to be fed either 3.5 kg (8 lb) of performance cubes or 2 kg oats, 1 kg cubes and 0.5 kg beet pulp. The first ration falls within its appetite of 12.5 kg. In most cases this small amount may not be of consequence, but a fussy feeder may let you know that the ration is rather too much. Step Seven: Checking the Protein Level Energy is the most important aspect of a performance horse's diet, and if good quality feed is being used the protein requirements are likely to be satisfied. However, growing youngstock and brood-mares will have a high protein requirement (see Table 13.10) and it is important to check the protein level in any ration that you have formulated. From Table 13.10 it can be seen that a horse in medium work requires 7.58.5% crude protein. The protein content of the ration can

< previous page

page_174

next page >

< previous page

next page >

page_175

Page 175 Table 13.10 Protein requirements of horses. Type of activity

Crude protein in the ration (%)

Light work

7.58.5

Medium work

7.58.5

Hard work

9.510

Fast work

9.510

Pregnant mare first 8 months

7.58.5

Pregnant mare last 3 months

10

Lactating mare first 3 months

12.5

Lactating mare last 3 months

11

Stallion

9.510

Weanling

16

Yearling

13.5

Two-year-old

10

be worked out as shown in Tables 13.11 and 13.12 using the nutrient values given in Table 13.8.

If the hay is low in protein, which is not unusual, and the oat-based ration is used the calculation would be as shown in Table 13.12.

This is not adequate for a horse in medium work; if the hay is low in Table 13.11 Protein in ration A (hay and cubes). Feed

Quantity (kg)

Protein content (%)

Protein in ration (g)

Hay

9

6

540

Performance cubes

3.5

13

455

12.5

995

< previous page

page_175

next page >

< previous page

next page >

page_176

Page 176 Table 13.12 Protein in ration B (oat-based ration). Feed

Quantity (kg)

Protein content (%)

Protein in ration (g)

Hay

9

4.5

405

Oats

2

10

200

Cubes

1

13

130

0.5

7

35

Beet pulp

12.5

770

protein make sure that the concentrate ration supplies adequate protein by using either a high protein feed like soya or performance cubes. Step Eight: Checking and Adjusting the Ration All horses are individuals and must be fed accordingly. Once a ration has been calculated and is being fed, the horse must be monitored to ensure that the ration is suitable. (1) A supply of clean, wholesome water must be available to the horse at all times. (2) The foods must be of good quality and acceptable to the horse is the horse enjoying its food? (3) Not only must the foods satisfy the horse's nutritional requirements: the horse must also be psychologically satisfied, i.e. it must not suffer boredom or have a craving for roughage. (4) The horse's condition must be checked by eye, tape or weighbridge. The horse may be gaining or losing weight: is this satisfactory? If not, alter the ration accordingly. Horses have optimum performance weights, and the horseowner should be aware of this weight for each individual. (5) The horse's temperament and behaviour may affect the ration fed. Part-bred horses may need more corn and less bulk as they are better doers and (usually) more placid. Routine and a quiet yard may save feed as horses are not fretting in their boxes. (6) The horse's environment must be noticed. In a cold spell, more food and an extra blanket may be needed. (7) Horses must be regularly wormed and have their teeth checked for sharp edges.

< previous page

page_176

next page >

< previous page

page_177

next page > Page 177

(8) Some are poor doers, perhaps due to a gut damaged by worms early in life, and will always need extra attention in their feeding. Ration Calculations Ration for a 162 cm (16 Hands) Novice One-Day Event Horse limited period at grass every day schooled and/or hacked for 6090 minutes every day three feeds a day. Step 1: Estimation of Bodyweight (Table 13.5) = 500 kg Step 2: The Horse's Appetite (Table 13.5) = 12.5 kg (27.5 lb) Step 3: Energy for Maintenance

= 18 + 50 = 68 MJ DE/day Step 4: Energy for Work (Table 13.6).

Total Energy Requirement /day = 118 MJ DE Step 5: Forage to Concentrate Ratio (Table 13.7)

< previous page

page_177

next page >

< previous page

next page >

page_178

Page 178 Step 6: Making the Ration Feed

Quantity Energy in feed (MJ DE/kg)

(kg)

(lb)

Energy in ration (MJ DE)

Hay

8

9

20

72

Performance mix

12

2.5

5.5

30

Sugarbeet pulp

10

0.45

1

4.5

Alfalfa chaff

10

0.45

1

4.5

Sunflower oil

35

250 ml

0.4 pt

9

Total energy

120

Step 7: Checking the Protein Feed

Quantity (kg)

(lb)

Protein content (%)

9

20

8

Performance mix

2.5

5.5

12

Sugarbeet pulp

0.45

1

7

Alfalfa chaff

0.45

1

15

Sunflower oil

250 ml

0.4 pt

0

Total

12.5 kg

Hay

% protein in ration

Protein in ration (g) 720 300 30 70 0 1120

9

Step 8: Checking and Adjusting the Ration As the horse is out to grass during the day, the hay ration would be adjusted depending on the quantity and quality of grass available. The horse would be given electrolytes to replace the salts lost in sweat. If cereals are used instead of mix a general purpose supplement would be added to the ration. Ration for a 162 cm (16 Hands) Advanced Three-Day Event Horse limited period at grass every day schooled and/or hacked for 6090 minutes every day; fast work every 4 days three feeds a day.

< previous page

page_178

next page >

< previous page

next page >

page_179

Page 179 Step 1: Estimation of Bodyweight (Table 13.5) = 500 kg Step 2: The Horse's Appetite (Table 13.5) = 12.5 kg (27.5 lb) Step 3: Energy for Maintenance

= 18 + 50 = 68 MJ DE/day Step 4: Energy for Work (Table 13.6).

Total Energy Requirement/day = 138 MJ DE Step 5: Forage to Concentrate Ratio (Table 13.7)

Step 6: Making the Ration Feed

Energy in feed (MJ DE/kg)

Energy in ration (MJ DE)

Quantity (kg)

(lb)

Hay

8

6.5

14

52

Performance mix

12

5.5

5.5

66

Sugarbeet pulp

10

0.45

1

4.5

Alfalfa chaff

10

0.45

1

4.5

Sunflower oil

35

250 ml

0.4 pt

9

Total energy

136

< previous page

page_179

next page >

< previous page

next page >

page_180

Page 180 Step 7: Checking the Protein Feed

Quantity (kg)

(lb)

Hay

6.5

14

Performance mix

5.5

5.5

Sugarbeet pulp

0.45

1

Alfalfa chaff

0.45

1

Sunflower oil

250 ml

0.4 pt

Total

13 kg

% protein in ration

Protein content

Protein in ration

(%)

(g)

8

520 12

660

7

30 15

0

70 0 1280

9.8

Step 8: Checking and Adjusting the Ration As the horse is out to grass during the day, the hay ration would be adjusted depending on the quantity and quality of grass available. Feeding haylage or better quality hay would reduce the bulk of the ration and increase both energy and protein if required. The horse would be given electrolytes to replace the salts lost in sweat. If cereals are used instead of mix a general purpose supplement would be added to the ration. Conclusion These rations are only specimens of the type of calculation which can be used. These calculations are not intended to take the art out of feeding horses, but to remove some of the guesswork. The 'art' comes in keeping horses happy and in peak condition for long periods of time and recognising which ration suits an individual horse. There are no formulas for this just experience, for which there is no substitute.

< previous page

page_180

next page >

< previous page

page_181

next page > Page 181

14 The Utilisation of Nutrients during Exercise Introduction For a cell to stay alive and to function, it has to be able to extract and use the chemical energy locked inside the endproduct of soluble carbohydrate digestion, namely glucose. When a molecule of glucose is broken down, carbon dioxide, energy and water are released. If this reaction were carried out in a laboratory this energy would be released as heat which could be used to perform work, as in a steam engine. However, in the cell some of this energy is captured by transferring the energy lost from the glucose directly to another chemical compound, known as an energy carrier molecule. In all living cells from bacteria to man the major energy carrier molecule is adenosine triphosphate (ATP). This molecule consists of an adenosine body with three phosphate attachments, when one of the phosphates is lost energy is released (see Fig. 3.7). This energy can be used to perform work by the cell, such as muscle contraction. Energy Sources for the Equine Athlete Energy is stored in the horse's body in the form of glucose, glycogen, fat and protein. This energy is transferred to ATP and then used to fulfil the cell's energy requirements. The equine athlete needs energy to carry out the work being demanded of it, whether it be for racing, eventing, polo or dressage. It also requires energy for carrying out living processes such as breathing, eating and staying alive, and this is known as the energy for maintenance. Energy exists in several forms for example, light, heat, electrical, chemical and mechanical energy. All living organisms survive because they have the ability to convert one form of energy to another, for example releasing the chemical energy stored in ATP to provide the mechanical energy of moving muscles. The energy for life on earth originates from the sun, but this radiant solar energy cannot be used directly by horses for growth or work.

< previous page

page_181

next page >

< previous page

page_182

next page > Page 182

However, plants use energy from the sun in the process of photosynthesis, in which this energy is converted into chemical energy and stored in the leaves of plants. This chemical energy becomes available to the horse when it eats the plants. A by-product of photosynthesis is oxygen which we need to breathe to stay alive, and this is one reason why the destruction of the rain forests poses a serious threat to our environment. Thus the free energy of solar radiation is trapped by plants and converted into chemical energy (carbohydrates, fats and protein); the cells of the horse's body carry out complex and imperfectly understood reactions by which this chemical energy is made available to supply the energy required for growth and work. All these life processes utilise energy in the form of ATP. The chemical energy from the horse's food (plants) is transferred to the horse's body cells where, by complex chemical reactions the energy is 'coupled' on to ATP. When the horse requires energy, the ATP is broken down with the release of energy. This allows biological work such as muscle contraction to be performed. The Energy Requirements for Work. The horse's energy requirements for work depend on many factors including: speed of work duration of the work terrain incline the weight of the horse the horse's fitness rider/driver ability environmental temperature and humidity the horse's soundness and conformation. At one extreme a sprint race of 1200 metres (6 furlongs) theoretically increases a horse's daily energy requirements by a mere 4%, while a day's hunting would more than double the day's energy requirement. In sprint races most of the energy for muscle contraction is obtained by the anaerobic breakdown of glucose, whereas long distance horses like eventers, hunters and endurance horses use a combination of anaerobic and aerobic energy production, where glucose is burnt up in the presence of oxygen to produce the energy for prolonged muscle contraction.

< previous page

page_182

next page >

< previous page

page_183

next page > Page 183

Training involves priming the horse's body systems so that the horse can do the work demanded of it with maximum efficiency and minimum fatigue. The Protein Requirements for Work The horse's dietary requirement for protein is not greatly increased by work; the loss of protein in sweat and the need for more protein to be incorporated into the greater muscle mass of the fit horse demands an increase of only about 2% more protein in the diet. As the horse works the energy requirement increases substantially and the concentrate ration fed to sustain this energy requirement very often increases the protein component of the ration sufficiently to meet the extra protein demand. In other words, providing that you are feeding good quality food, look after the energy and the protein will look after itself. Horses with high energy requirements do not need to be fed high protein feeds, unless they are being fed extremely poor hay, with a protein content of below 6%. The feeding of excess protein may, in fact, be detrimental to performance, with horses not racing as fast and sweating and blowing more heavily. The exceptions to these statements are the 2- and 3-year-old racehorses in training, which are still growing and consequently have a high protein requirement. Good quality protein is essential for performance horses. This supplies a better balance of essential amino acids (building blocks of protein). Table 14.1 The protein needed for different types of work. Work level Light Medium Hard Fast

Crude protein in the ration (%) 7.58 7.58 9.510 9.510

The Utilisation of Nutrients during Exercise Energy is the major nutrient requirement of the adult performance horse; the chemical energy in feed is converted into energy for muscle contraction so that the horse can do the work we demand of it. At one

< previous page

page_183

next page >

< previous page

page_184

next page > Page 184

extreme this work may be a sprint over 1200 metres (6 furlongs), at the other a 160 km (100 miles) ride at an average speed of 13 km/h (8 m.p.h.). The physiological body processes that produce energy for either speed or endurance are quite different; theoretically a short flat race barely increases the horse's daily energy requirements, while a 160 km (100 miles) ride would increase energy requirements five- or sixfold. The different training regimes for different disciplines take this into account and, as we have seen, the body changes that result from a fitness programme vary accordingly. Throughout training the horse's diet must be formulated to allow for these changing needs, taking into account the fact that as a horse gets fitter his appetite may well fall so that he goes off his feed. For a horse to be receiving the best nutrition for the job it is doing, each cell in each tissue of its body must be getting an adequate supply of nutrients for energy production. Energy production results in certain waste products which must be disposed of as efficiently as possible to prevent their build-up, which would otherwise cause the horse fatigue. The way food and nutrients are used in the horse's body is affected by several factors: the horse's health the horse's fitness and type of training the environmental temperature the diet the amount of nutrients already stored in the horse's body. Feeds which supply energy, water and electrolytes are all very important it is clear that feeding and training must work together in harmony to produce the truly fit equine athlete. Training and Energy Expenditure The whole idea of getting horses suitably fit for high performance is to alter the entire metabolism of the horse to allow it to function at maximum efficiency with minimum fatigue during its particular discipline. The amount of energy used will vary depending on the type of work and the size of the horse (Table 14.2). Horse-owners have known this for years and have summarised it in one of the 'rules of feeding': feed according to work done. Walking, which is generally accepted to be an extremely good form of exercise for toning muscles, tendons and ligaments, barely increases the horse's daily energy requirement above maintenance. Strenuous or

< previous page

page_184

next page >

< previous page

next page >

page_185

Page 185 Table 14.2 Digestible energy (DE) demands of maintenance and work. Bodyweight (kg)

200

400

600

Maintenance requirement/day (MJ DE)

35

58

79

0.4

0.8

1.3

4.2

8.4

12.5

10.5

20.9

31

25

50

75

42.0

85

127

43.5

87

130.5

Energy requirement for work (MJ DE/day): One hour walking One hour slow trotting, some cantering One hour fast trotting, cantering, some jumping Cantering, galloping and jumping Strenuous effort, racing, polo Endurance work, 100 km in 10.5 hours

extended effort increases the horse's requirement to such an extent that the horse physically cannot eat enough energyproviding food in one day to satisfy the extra demand. This, combined with the fact that hard work often reduces the horse's appetite, means that recovery from hard work requires several days for the horse's energy reserves to be replenished. In these cases, appropriate use of oil or a concentrate ration containing high levels of oil will be beneficial. This enables horse-owners to give the horse energy in a more concentrated form, i.e. less volume of hard feed. Even though during hard work a horse will use up more energy than it can consume during the day, we must not feed it to fortify it for future events because any energy supplied over and above immediate needs will be stored as fat and fatness will impair performance. Overfeeding can also lead to problems such as filled legs, laminitis, colic, muscle myopathy and excitability. Sources of Energy to the Muscles The two major sources of energy for the horse are carbohydrates and fats; except during starvation proteins are of little importance for this purpose. The energy for muscle contraction is derived from high energy phosphate compounds (ATP and creatine phosphate), which in turn come from the glucose, free fatty acids and volatile fatty acids which result from the breakdown of food in the horse's gut. The glycolytic pathway converts glucose to pyruvic acid with the release of ATP. This process transfers some of the chemical energy of glucose to ATP in the absence of oxygen. In the presence of oxygen, glucose is

< previous page

page_185

next page >

< previous page

page_186

next page > Page 186

broken down completely to carbon dioxide and water. This takes place in the mitochondria of the cell and results in further ATP production. During digestion, fat is broken down to fatty acids and glycerol; fatty acids are converted to acetyl CoA and enter the tricarboxylic acid cycle to be broken down to carbon dioxide and water with the transfer of energy to ATP. The breakdown of fat leads to the synthesis of about two and a half times as much energy per gram as the breakdown of a gram of glucose. Glucose is absorbed into the bloodstream and the blood glucose is a readily available source of energy. Excess glucose is stored as glycogen in the liver and muscles, ready for mobilisation and energy production when necessary. If the horse is overfed, further glucose is stored as body fat. The liver has a role in regulating blood glucose levels by breaking down glycogen to glucose to top up blood sugar when needed during exercise and by storing blood sugar as glycogen after a meal. Glucose is broken down in the muscle cells to create ATP; maximum energy is released when there is an adequate supply of oxygen arriving in the blood. Immediate and rapid release of energy can take place in the absence of oxygen in a process known as anaerobic respiration; the resulting chemical compound, pyruvic acid, can only be completely broken down to carbon dioxide and water in the presence of oxygen. In the absence of oxygen, pyruvic acid is broken down to lactic acid, which eventually also needs oxygen to be broken down to harmless substances in the liver. The more anaerobic respiration (sprinting) the horse undergoes, the more lactic acid builds up, and the more oxygen will eventually be required to break it down. This is called the 'oxygen debt' and is repaid when the sprinter blows after its race. Anaerobic respiration yields less energy than aerobic respiration. During extended work the healthy, fit horse easily breaks down fatty acids to carbon dioxide because there is enough oxygen being breathed in to cope with the energy demand. The changing demands of the horse for energy are regulated by the secretion of a number of hormones; as the racehorse leaves the starting stalls, its nervous system stimulates the release of hormones which cause essential changes in the body systems involved with exercise, such as the heart and blood vessels. Some hormones affect the enzymes that regulate the chemical reactions involved in energy production; other hormones, such as insulin, influence the permeability of cell membranes, so that the cells can take up more glucose, causing blood sugar levels to fall.

< previous page

page_186

next page >

< previous page

page_187

next page > Page 187

Resting blood sugar levels tend to be higher in horses trained for sprinting. This is caused by stimulation, not only of the systems which form glucose, but also those which spare glucose by encouraging the use of fatty acids during exercise. Blood glucose also fluctuates during day and night; it peaks 23 hours after feeding, the height of the peak depending on the type of diet. Rations containing more grain and less roughage lead to higher peaks after feeding and lower troughs when the horse is hungry. Horses on a roughage-based diet become better at making glucose from other absorbed nutrients, so that they can resist a fall in blood glucose more easily when hungry. They are not, however, able to meet the high glucose demands of exertion. There are also breed differences: Thoroughbreds have a high insulin sensitivity and consequently their blood sugar levels vary more than those of a pony on the same diet. This could partially explain the more volatile temperament of the Thoroughbred. As the intensity of training increases, the demand for energy released by a particular metabolic pathway also increases, as does the need for the appropriate enzymes to help the reactions along. Sprinting is primarily anaerobic, and training increases the horse's ability to break down glucose in the cytoplasm of the cell, with the enzymes that help prevent a build-up of lactic acid being present at nearly twice the untrained level. Longer periods of fast work involve aerobic processes; consequently the training of these horses results in an increase in the numbers of 'powerhouses' or mitochondria present in the cell. The mitochondria house the enzymes needed for the aerobic production of energy. Enzymes need substances called co-factors in order to function properly; as the concentration of enzymes increases so the need for these co-factors is increased. Co-factors include the minerals, magnesium and zinc along with several B-complex vitamins; this may indicate that horses in training require a dietary supplement of these micronutrients. Hormonal Effects Hormones are chemical messengers produced by the glands of the endocrine system. Their job is to travel round the horse's bloodstream so that complex messages and commands can be delivered. The endocrine system and the nervous system work together, although hormones tend to give slower but more long-lasting messages than the instant commands of the nervous system. The activity of many of the enzymes involved in energy production is regulated by hormones such as insulin, glucagon and adrenalin.

< previous page

page_187

next page >

< previous page

page_188

next page > Page 188

Insulin After eating and digesting a meal, glucose floods into the horse's bloodstream and this stimulates the release of insulin from the pancreas. Its task is to slow down the breakdown of glucose and to encourage it to pass into the body cells, with any excess being stored as glycogen in the muscles and liver or as fat for later use. Insulin makes it easier for glucose to pass into the muscle cells. Horses on a high concentrate diet adapt to the high carbohydrate content of their food by having a high insulin activity. This, however, may be a problem, particularly after a large concentrate (grain) feed. The increase in blood glucose will lead to insulin release. If the horse is worked at this time, insulin will be storing this glucose instead of mobilising it as is required for the exercising horse. Horses should not be exercised for at least 2 to 3 hours following a feed. Ideally, competing horses should be fed forage little and often before an event, to reduce insulin surges. The benefit of glucose mobilisation outweighs the disadvantage of the gut-fill weight factor. In summary, forage should play a greater part in the management of athletic horses. It should provide the basis of the overall diet, whereas many competition horses have been fed forage as a 'bulk' feed only. The better the quality of forage, the less concentrates will be needed. Glucagon If the effects of insulin were not controlled, blood sugar levels would continue to fall to dangerous levels. The hormone glucagon ensures that this does not happen. Glucagon brings about an increase in blood sugar levels by stimulating the enzymes (which, like insulin, are produced by the pancreas) that break down the glycogen stored in the horse's liver. Adrenalin Adrenalin (epinephrine), produced by the adrenal glands, is the 'flight or fight' hormone. A racehorse leaving the starting stalls jumps into explosive activity and needs energy immediately; the sympathetic nervous system stimulates the release of red blood cells stored in the spleen and the secretion of adrenalin from the adrenal medulla. Adrenalin has many effects, including an increased heart rate, higher blood pressure, contraction of the stomach, reduced intestinal activity

< previous page

page_188

next page >

< previous page

page_189

next page > Page 189

and the mobilisation of liver glycogen accompanied by a rapid rise in blood glucose levels. Glucocorticoids (Cortisol, Cortisone and Corticosteroid). This group of hormones is also produced by the adrenal glands; they are involved with encouraging higher blood sugar levels by creating glucose from alternative energy sources such as stored fat and protein. The glucocorticoids do not respond as quickly as adrenalin to work demand; their secretion relies on hormonal messages from the pituitary gland situated at the base of the brain. Training and fitness allow the horse to develop the adrenocorticoid response so that it is able to maintain its blood sugar levels more effectively under the stresses of sprint and endurance work. Acidosis and Alkalosis The acidity of the horse's blood and body tissues, expressed as the pH, is kept within strictly defined limits, normally within 7.47.5. The carbon dioxide carried in the blood to the lungs and haemoglobin prevent the pH of the blood from changing too much and causing the horse to become ill. This is known as a 'buffering' effect. Bicarbonate ions also act as a buffer, giving up hydrogen ions when the blood becomes more alkaline and absorbing them when it becomes more acidic. The acidity of the horse's blood can become upset under certain circumstances; if the blood becomes more acidic than normal the condition is known as acidosis, if the blood becomes less acidic than normal the condition is called alkalosis. Metabolic Acidosis During fast, hard work, lactic acid will accumulate in the tissues and pass into the bloodstream resulting in acidosis, but this state is only temporary and the horse's body mechanisms will soon oxidise the lactic acid and restore the balance to normal. Horses are sometimes given 250300 g of sodium bicarbonate over 24 hours as a treatment for metabolic acidosis, but care should be taken as too much bicarbonate can cause further problems. Metabolic Alkalosis Metabolic alkalosis can occur in exhausted horses, particularly after long-distance work in hot weather. When the horse sweats it loses

< previous page

page_189

next page >

< previous page

page_190

next page > Page 190

electrolytes such as potassium and chloride ions, and if sweating is prolonged these may become depleted and hydrogen ions are excreted instead. Their place in the body fluids is thus taken by alkaline bicarbonate and alkalosis results, shown in severe cases as tetanus-like muscle spasms. Mistakenly giving the horse sodium bicarbonate under these circumstances would make the alkalosis much worse; instead a balanced electrolyte solution containing sodium, potassium, chloride and glucose should be given. Respiratory Alkalosis If a horse works hard in hot conditions the heat loss systems such as sweating may not cool the horse fast enough to prevent it from becoming overheated. Overheating affects the respiratory centre of the brain, resulting in a more rapid breathing rate; hyperventilation flushes more carbon dioxide from the blood than usual and the blood pH rises the blood becomes more alkaline. Respiratory Acidosis The breathing rate of a sprinting racehorse is regulated by stride frequency; consequently the rapid shallow breaths taken by the galloping horse do not clear carbon dioxide from the blood adequately, and as carbon dioxide levels rise the acidity of the blood rises. Horses with diseased lungs or reduced lung capacity due to allergy will also experience respiratory acidosis. For the horse to remain fit and healthy it is important for the acid-base balance of the blood to be maintained as close to normal as possible. As we have seen, the acidity of the blood can be altered by the loss of ions like bicarbonate, potassium and sodium. These losses occur most dramatically in the sweating horse, and the care of the horse working in hot and humid climates requires good management from rider and groom with the provision of suitable electrolytes in the feed or water. Feeding for Performance The eventual performance of a horse is dependent on many factors, but no matter how well trained the horse is, if it is not fed properly it will not perform at its best. Both overfeeding and underfeeding are detrimental, and the horse must be fed for its immediate needs and not stoked with food to fortify it for future work. Overfeeding causes

< previous page

page_190

next page >

< previous page

page_191

next page > Page 191

fatness, metabolic problems such as tying-up, temperament problems, filled legs, and bumps under the skin. Underfeeding results in a thin horse, which lacks the muscle development and energy stores to work at its best. The difference in the metabolic processes by which energy is produced for sprinting work and endurance work means that long-distance and endurance horses have to make effective use of body fat reserves to provide energy and to conserve glucose sources. Studies have shown that horses can digest dietary fat, such as corn oil or vegetable oil, well, and that oil can be used to replace some of the cereal ration. Fat in the diet also slows down the fall in blood glucose during endurance rides, due to its 'glycogen-sparing' effect. In other words, oil provides an alternative energy source for horses doing long, slow work. Levels of oil as high as 810% of the total ration have been suggested; in practical terms this would amount to 11.5 litres every day for a 500 kg horse. The authors have successfully fed up to 500 ml per day to horses in hard work, but have no experience of feeding these much higher levels. Adding 500 ml of oil to your horse's feed will enable you to reduce its concentrate by 11.5 kg of oats, depending on the quality of the oats. It has been suggested that the endurance or long-distance horse should have its concentrate ration built up by an extra 1 kg per day for the 2 days preceding the ride, with the roughage being reduced by 2 kg. This is to ensure that the horse has adequate energy stores for the strenuous work ahead of it. On the day of the ride the horse may have a small concentrate feed and free access to water, but hay should not be given. Whatever the discipline, work should always be kept ahead of feed, so that concentrate intake is increased as the intensity of work increases. In all cases, make sure that hard feed is dramatically reduced by at least half if the horse has a rest day; the hay ration should be increased so that the horse does not go hungry. If the rest is enforced through injury or illness and is likely to be of a long duration, it may be wise to cut back the concentrates even more than this. A little loss of condition is preferable to azoturia or similar problems.

< previous page

page_191

next page >

< previous page

page_192

next page > Page 192

15 Care of the Performance Horse Stress The word 'stress' occurs frequently in talking about competition horses, and it is important to understand the implications of stress. Any competing horse is under stress, and the best performers may be those best able to tolerate it. The rider and trainer must be concerned about the degree of stress a horse can be exposed to without causing harm and suffering. It must be remembered that stress is a natural and normal response to daily variations in the environment. Within limits, the stress response will help, ensuring adaptive response this means that the next time the same situation arises the horse will not find it so stressful because it has previously adapted to that situation. The most obvious example of stress to which a horse is exposed during training is a progressively increasing workload. Each time the horse is worked, a new level of stress is introduced, leading to fitness to cope with a predetermined level of exercise. In other words, stress is a necessary and desirable part of a horse's training programme. If the horse cannot cope with the level of stress to which it is being exposed, it becomes distressed obviously, overstress is not desirable. Many performance horses are subject to repetitive competition stress, and the rider and trainer must remember that each competition involves more that the physical stress of jumping and galloping. The stress of travelling and the mental stress of being in a crowd and away from home will also take their toll. Competition also involves the grouping together of large populations of horses, any of which may be suffering from obvious illness or subclinical disease (the horse is ill but showing no symptoms). Chronic stress reduces a horse's resistance to disease, a factor which may explain why so many horses succumb to viral infections. This is particularly true in racehorses, where the animal is under the added stress of growing and performing at the same time. There is no doubt that the stressful conditions imposed on com-

< previous page

page_192

next page >

< previous page

page_193

next page > Page 193

petition horses are most often caused by lack of knowledge or ability on the part of the rider or trainer. This leads to poor management, training and riding, exacerbating the stress the horse is already under. Riders and trainers must be aware of an individual horse's ability to cope with stress and treat each horse accordingly. This is where the 'art' of training takes over from science anybody can get horses fit, but not everybody can keep them that way. Care after the Event. After the horse has finished a high-stress competition, it will benefit from efficient and thoughtful treatment. The horse's temperature, pulse and respiration will all be elevated, and it is important to get these systems back to normal as quickly as possible. Keep the Horse Moving Immediately after the work has stopped, the rider should dismount and loosen the girth. Now is not the time to untack it is more important to keep the horse walking so that the circulating blood will cool the muscles and carry toxins such as lactic acid away from the muscles. Standing reduces circulation so that lactic acid may be 'trapped' in the muscles, causing stiffness and perhaps inducing azoturia (tying-up) or even colic. After 5 minutes' walking the horse can be untacked, a sweat rug or cooler put on and walking continued. If the saddle has been on for a very long time, it should be left on for longer than 5 minutes to allow the circulation in the blood vessels under the saddle to return. Sudden removal of the saddle can cause pressure lumps and scalded backs. Check TPR The temperature, pulse and respiration should be taken to see how much above the normal they are and to monitor how quickly they drop. These values are an indication of how severely stressed the horse is, and how quickly it is recovering. The pulse can be taken under the jaw or using a stethoscope for 10 seconds multiplying by six to get the pulse rate per minute. The temperature may be up to 43°C (106°F). The quality of respiration should be noted; a horse breathing deeply is taking in oxygen, while rapid, shallow breaths indicate that the horse is trying to cool down. On average, in a fit horse, it takes about 15 minutes for the pulse

< previous page

page_193

next page >

< previous page

page_194

next page > Page 194

and respiration to return to comfortable limits. The horse should be checked every 15 minutes until the values return to normal, which should be within an hour of completing exercise. Washing Down The horse should be walked for 15 minutes until the breathing has slowed, and then stood in a sheltered place out of the wind on a cool day and out of the sun on a hot day. If the horse's temperature is no more than 41°C (104°F), cool water will cool down the horse quite safely. The lower neck, inside the legs, the head and the belly should be sponged. The large muscles of the back and quarters should be avoided, as sudden cooling may send these muscles into spasm. If the horse's temperature is between 41 and 43°C (104 and 106°F) and the weather is hot and humid, the horse must be cooled as rapidly as possible. Ice water can be used on the horse in strategic places, e.g. under the tail, between the hind legs and on the head, where major arteries pass close to the skin, thus having a maximum cooling effect. The loins and quarters must be avoided. It is important to keep the horse moving, one person leading and one sponging the horse. If the muscles are shaking from stress, the horse must be walked as it is sponged. Water Provision The horse must not be given water until the temperature has dropped to 40°C (103°F) and the pulse and respiration have slowed. When a horse is exercising, adrenalin stimulates the blood vessels to the stomach and gut to contract, sending blood to the muscles. While the horse is cooling down, the blood must be kept in the muscles. If it drinks cold water the blood vessels to the stomach dilate and blood rushes to the stomach, away from the muscles, legs and feet. The horse will cool less efficiently and may even become colicky. Once recovery is under way, and until the horse is completely cool, five swallows of water for every 50 yards walked is adequate. Checking for Injury During untacking and sponging, the horse must be checked over for scratches and minor injuries which may become swollen and infected by the morning. Any injuries found should be thoroughly cleaned and dressed with antibiotic cream or powder, but bandages must not be

< previous page

page_194

next page >

< previous page

page_195

next page > Page 195

put on until the horse is cool. While the horse is being walked around it should be jogged for a few yards to check for soundness. Once cool and dry, the horse can be rugged up and returned to its box to rest. The legs can now be poulticed or bandaged (Fig. 15.1). Some people like to use a liniment and give the horse's legs a gentle run-down to help circulation and ease tension, while others use cooling treatments such as clay poultices.

Fig. 15.1 A stable bandage. Keep Checking The horse may break out in a sweat because, although the skin and surface muscles are cool, there may be heat and toxins deeper inside the muscles which the body needs to get rid of. The horse should be looked at every 10 minutes for the next hour, checking for cold sweaty patches, restless behaviour, disturbed bedding and reluctance to eat or drink. If all the lactic has not been removed from the muscles, these

< previous page

page_195

next page >

< previous page

page_196

next page > Page 196

signs could indicate the onset of tying-up or colic. If the signs of discomfort are only mild, the horse should be kept warm and walked in-hand until the sweat has dried and the horse is comfortable. If the horse is pawing the ground and looks very distressed, veterinary advice should be sought. The horse must be checked again last thing, and if they are at all worried it is wise for the rider or groom to look at the horse again during the night. It is sometimes advisable to walk the horse for 5 minutes at the check to ease any stiffness it may be feeling. Feeding Many riders worry about the amount their horses eat during a two- or three-day event competition. However, there is no need to worry too much. The horse has more than enough stored energy in its liver and muscles to see it through the competition next day. Do not depart from the horse's normal feed, as this may compromise the hind-gut bacteria. The fluid and electrolyte balance is very important, and the horse must be constantly watched for signs of dehydration. If a pinch of skin on the neck lingers after it has been released, and the horse has a gaunt, tucked-up appearance, it may well be dehydrated this really can limit the next day's performance. Ensure that the horse drinks, and provide electrolytes in the water and feed. Colic can be a problem after severe exertion, and the intestines must be kept moving. Once the horse is cool it may appreciate a small hay net, with its normal ration given later on. The tired horse is easily overfaced by a large feed, but dividing the normal feed into two and feeding it at intervals may overcome this. Signs of Overstress (1) Heat, swelling and pain in a specific area, indicating injury. (2) Reluctance to eat, restlessness, listlessness any sort of abnormal behaviour may indicate the onset of colic. (3) Shaking indicates acute muscle fatigue, and is the result of toxic lactic acid build-up and electrolyte imbalance in the muscle. The horse must be kept warm and walked in-hand to keep the blood flowing through the muscle otherwise the horse may tie-up. (4) If the horse is reluctant to move or get up and appears to be in pain (increased pulse and respiration), it may be suffering from

< previous page

page_196

next page >

< previous page

page_197

next page > Page 197

muscular myopathy or laminitis. The vet should be called if the signs persist. (5) Thumps (synchronous diaphragmatic flutter) is a condition where the horse shows rapid breathing with a distinctive thumping in the flanks as if the heart were beating there. Thumps occurs in horses that are nearly exhausted and is caused by an electrolyte and acid imbalance in the body. Immediate veterinary attention is necessary. (6) The horse's appetite will tell you how tired it has been. Until the horse is eating up normally, it has not recovered from its exertions and should be allowed plenty of rest. Hacks and grazing in-hand will help the horse relax and recover. Measures to Take to Reduce Stress. Always warm up the horse properly. The muscles should be supple and the horse alert and moving freely. Warmingup for too long exerts the horse unnecessarily, using up valuable energy stores, while lack of warming-up may mean the horse has to compete with the body systems unprepared, increasing chances of injury. Assess the horse. It is vital to know how fit your horse is, and at what speeds within paces it works best; this way you can work the horse to give its best performance without overstressing it. Judge the pace so that the horse is not too tired, and adjust the speed if necessary. It is the rider's job as well as the vet's to ensure that the horse is fit to continue. Use the rests and breaks between classes or phases of the competition intelligently. The procedure at rest stops should follow the same lines as the early stages of cooling the horse down after the competition. The horse must be kept moving a 20 metre walk every minute or so would be adequate. A rug should be thrown over the horse if the weather is cool, and shade found if the day is hot. Temperature, pulse and respiration should be checked. The horse can be allowed a few swallows of water if it is not badly overheated; most horses in endurance competitions learn to drink when water is offered. Tack should always be checked for safety and comfort, and changed if necessary. Take the horse's normal feeds with you to the competition. Stick to the same brands so that there is no sudden change in the horse's diet which could upset its appetite or digestive system. The routine at competitions should be as close as possible to the routine at home. Horses are creatures of habit, and thrive on routine.

< previous page

page_197

next page >

< previous page

page_198

next page > Page 198

The horse should be allowed to relax as much as possible at a competition. Grazing in-hand can accomplish this. The horse must be thoroughly checked the day after for soundness the legs looked at, the horse jogged and handwalked or turned out to roll and graze. The temperature should be taken; a rise in temperature could indicate illness. Horses weakened by the stress of exertion are more susceptible to illness and disease. The horse must be travelled carefully. The legs and head should be adequately protected and the vehicle driven with great care. Travelling can be exhausting for a tired horse and long distance journeys should be undertaken thoughtfully, stopping frequently to water the horse and perhaps allowing it to stretch its legs. In the U.S.A., horses are subjected to very long journeys. Travelling in high temperatures can lead to dehydration which in turn can cause impaction of the intestine and colic. Feed only hay and a good supplement before travelling. Following these procedures before, during and after competition will help minimise the physical and mental stress to which the horse is exposed. In turn, this will help the horse enjoy a longer and more successful working life.

< previous page

page_198

next page >

< previous page

page_199

next page > Page 199

16 Interval Training and Getting the Event Horse Fit Training the Event Horse Probably more has been written about getting horses fit for eventing than for any other equine discipline. As with any performance horse, the ideal degree of fitness at any time depends on the stage in the total training plan, the ability of the rider and the realistic competitive goal. The Novice horse has a similar degree of fitness to the hunter, while the Advanced horse requires a fitness similar to that of the point-to-pointer. Indeed, traditional methods of training the eventer follow very similar lines to those given for hunters and point-to-pointers. Obviously, schooling in the three disciplines of dressage, show jumping and cross-country has to be incorporated into the training programme. Getting the Advanced three-day event horse ready to compete is another matter; this horse has to be supremely fit and yet disciplined enough to perform a demanding dressage test. The fitness programme has to ensure that the horse achieves a maximum level of fitness, while staying sound and keeping a reasonably calm frame of mind. Interval training is used by some riders, while others adhere to more traditional methods. In body condition, eventers lie between racehorses and show jumpers or dressage horses; being a 'jack of all trades' for distance, speed, power and control the eventer has to compromise. Eventers must be fast enough to gallop crosscountry within the time without distress, and yet they need to combine this with other talents and physical demands. Thus they are not as lean and wiry as National Hunt horses, though less well-covered than dressage horses they must avoid the strain of too much weight on their limbs and wind, and yet the dressage demands muscular development of the neck and back. The event horse has to gallop in a balanced, calm manner and in a round outline; it must be able to lengthen and shorten its stride and to cope with gradients while carrying the rider's weight. Many horses find this difficult and have to be taught to gallop the stuffy short-striding horse is a prime example, and it may have to be worked more

< previous page

page_199

next page >

< previous page

page_200

next page > Page 200

strongly than its longer-striding counterpart. Big long-striding horses may need working more slowly to keep them calm and balanced. A reluctant or lazy horse may benefit from galloping alongside another horse; this will teach it to enjoy galloping and make it try harder. When to Start It is wise to get the event horse up from its winter break in December rather than January; if the programme does not begin until after Christmas and the weather turns icy and snowy then there may not be enough time to do the road work thoroughly. If the walking work is done by January it is not the end of the world if the horse misses a few days' work. It is crazy even to consider going out on icy roads; if there is no access to an all-weather arena or indoor school it is sometimes safer to stay at home in front of the fire! It is difficult to think of a worse time to get a horse fit, with fog, rain, mud and freezing conditions, not to mention the lack of daylight. Good planning of the horse's stable management as well as the exercise programme will help survive those winter months. Stable Management during Fittening Vaccinations If the horse has not received its annual 'flu and tetanus boosters before its holiday, these should be given before starting any work. In a big yard it is easier to vaccinate the horses all at the same time, but this means that they will all be at maximum and minimum immunisation levels simultaneously. Horses working hard, travelling a lot and mixing with many different horses may justify a booster ever 6 to 8 months. Make sure that the information is recorded correctly on the certificate and that the diagram of the horse is absolutely correct. Teeth The horse's teeth are continually growing, and sharp or rough teeth can affect its condition. If a horse is uncomfortable in its mouth or in pain it will start playing with the bit or drawing its tongue back to evade the problem. Once this happens this may become a habit which can be very difficult to cure. In a young horse wolf teeth may need removing, and this will dictate a rest period to allow healing. The vet or horse dentist should check the horse's teeth every 6 months.

< previous page

page_200

next page >

< previous page

page_201

next page > Page 201

Worming All horses should have a regular and effective worming programme. Shoeing The horse's feet must be regularly trimmed or shod during its holiday valuable time must not be wasted by broken feet or cast shoes. Horses must be shod all round once their road work starts; a heavier set of shoes will last longer during this initial fittening period. Non-slip tungsten nails are a good way of helping cope with slippery roads; road studs tend to unbalance the foot as it hits the ground. The horse should be shod every 4 to 6 weeks; if left too long the foot becomes unbalanced, putting unnecessary strain on joints, tendons and ligaments. Tack. The tack should have been stored in good condition at the end of last season, checking the stitching and restuffing the saddle if necessary. The hard fit horse you last sat on has become soft, furry and probably fatter saddles and girths may no longer fit and poorly fitting tack will soon rub a soft horse's skin. This may cause visible sores and longer lasting pressure on muscles which may only come to light when the horse starts to work harder. A thick numnah and a girth sleeve are a good idea to prevent rubbing and absorb sweat, but these must be washed regularly with a nonbiological soap powder. Salt water or methylated spirits can be applied to the vulnerable areas to harden up the skin. (Methylated spirits should not be used if the skin is broken.) A breastplate may be needed to stop the saddle slipping, but this too can rub, and a soft covering may be advisable. A hunting breastplate allows a martingale attachment if needed. Clipping Even with a New Zealand rug the horse will have grown a winter coat and need clipping. A high trace clip is quite adequate while the horse is walking, and gives a safety margin should it have to stop work and return to the field or just be rested in its stable. Some people prefer to clip horses out as soon as walking commences, but it is important that horses are kept warm and dry on exercise if they are clipped out because walking does not produce much heat. Clipping the legs may improve a horse's appearance but leaves it with little protection against thorns and mud, and brushing boots rub more easily. In many

< previous page

page_201

next page >

< previous page

page_202

next page > Page 202

ways it is better to blanket clip and wait until spring comes before clipping the remaining hair off the back. A long, dirty winter coat will soon blunt clipper blades; blades may have to be changed frequently and time allowed for the clippers to cool off. The horse should be as clean as possible before clipping and the use of a 'hoover groomer' can be a great advantage. After clipping, extra rugs must be put on to keep the horse warm in the stable. Blood Tests Blood tests can be used to detect ill-health and ascertain levels of fitness, but it is important to build up a blood profile for each horse and not just do a one-off test. All horses have different blood pictures at peak fitness. Boots As a general rule, the horse should be exercised in front boots and knee boots; back boots can also be used if the horse's action requires them. Watch out for black ice and try to ride later in the morning to give the ice time to melt. If riding early or when the visibility is poor, in rain or mist, it is wise to invest in reflective clothing. There are many products on the market ranging from quarter sheets and boots to hat covers and coats. They may not be the height of fashion but they could prevent a serious accident. Riding in Snow If the roads are snowy, packing the inside of the hoof with grease or a thick layer of oil will help prevent the snow from balling in the foot; it will last for a while and help the horse keep its feet. A hoof pick is useful to clear the snow from the foot while on exercise. Turning Out The horse will benefit from being turned out during its fittening programme for a few hours every day this will help it unwind and stay sane. The horse has been accustomed to being out for most of the day and if part of its routine is a daily turn-out it is unlikely to have a wild fling and gallop about. A stable rug under its New Zealand will help prevent the wind from chilling the horse quickly, and a neck guard or hood will give additional warmth and save a lot of grooming time.

< previous page

page_202

next page >

< previous page

page_203

next page > Page 203

Horses turned out in muddy paddocks should be watched for mud fever on the legs. When washing off mud, rinse the legs in salt water and dry the legs with a clean towel or absorbent paper. A dusting of talcum powder will help dry legs and is especially useful if bandages have to be wrapped around damp legs. Getting the Event Horse Fit the Exercise Programme There are many ways of getting horses fit the method used depends on individual circumstances, facilities and routine. The two things on which all authorities agree are that the horse must be brought into work slowly and that the first month of work must consist of walk and trot on good going. This means that it is of utmost importance to allow enough time to achieve the level of fitness which is being aimed for. You must allow 3 months to prepare for the first event of the season, bearing in mind that showjumping, dressage and cross-country competitions may be part of the build-up. To achieve basic fitness, the programme outlined earlier for the hunter should be used: 2 weeks of walking work, followed by 2 weeks of walking and trotting. Unlike dressage or showjumping horses, it is vital to continue road work throughout the fitness and training programme. If the road work is skimped, sooner or later the horse's career will come to an abrupt halt. The One-Day Event Horse The following programme assumes that the horse has been turned out during the day, stabled at night, fed two concentrate feeds a day with hay at night, and is in good condition. Feeding Some horses may need only grass and hay to maintain or improve their condition while they are on holiday; others may also need concentrates. The amount depends on each horse, but is usually between 2 and 5 kg (4.5 and 11 lb) of feed a day. The problem starts when the walking exercise begins; if the horse's freedom is curtailed and its only exercise is when it is ridden, it may turn into a bucking bronco and the concentrate feed must be cut. A horse leaping around on the road is dangerous for rider, horse and other road users; unruly behaviour is always unnecessary. The concentrate ration should be gradually reduced often it is only a matter of 500 g to 1 kg (1 to 2 lb) and this

< previous page

page_203

next page >

< previous page

page_204

next page > Page 204

can tip the balance between a relaxed horse and one which is over-excited. It is far better to underfeed than overfeed the concentrates at this stage, but a lot of hay (or its dust-free equivalent) must be fed to prevent the stabled horse from becoming bored. Ideally the horse should be turned out every day to unwind; if a horse is only turned out periodically it can have so much energy stored up that it injures itself. It may be advisable to split the work into two sessions or to do a little trotting on good unpoached ground if the horse cannot be turned out and is getting above itself. Weeks 1 and 2: Walking. The walking commences in one of the following ways: (1) Walking for about 20 to 30 minutes a day, building up to 1 hour by the end of the first week and 2 hours by the end of week two. The horse is turned out for the rest of the day. (2) Walking starts as already outlined, but after exercise the horse is returned to its stable for the remainder of the day. (3) The walking can be split into two periods a day, starting with about 20 minutes for each session. (4) The horse may have only had a short holiday of 2 to 4 weeks; it is then walked two or three times a week for up to an hour each time. This helps to maintain a basic level of fitness and to keep the tendons and bones strong. The risk of girth galls and sore backs is also lessened. Once the horse starts to walk every day it can have 60 minutes of exercise. (5) A horse walker can be used to do most of the walking work, or the horse can be led off another horse. The problem is that this does not accustom the back muscles to carry a rider, and the girth region stays soft. Take care, if using a walker, that the speed is set so the horse walks out and does not just slop along. Ideally, the horse should be walked on the roads for up to 2 hours a day for 4 weeks and never less than 2 weeks the longer the holiday the more road work is needed. If the horse has been walked two or three times a week from the field, another 2 weeks on top should suffice once the horse has come in. Walking can become very boring and the weather is often cold and unpleasant, but the horse should always be walked on the bit or a long rein, never on a loose floppy rein this is bad discipline for both horse and rider.

< previous page

page_204

next page >

< previous page

page_205

next page > Page 205

Weeks 3 and 4: Trotting After at least 2 weeks of the initial walking work, trot can be introduced always go rising, on good ground and with the horse on the bit and balanced. The trotting can be alternated between the roads and grass or in the arena; a certain amount of trotting on the road helps the horse cope with hard ground, but too much causes concussion and jarring. Initially, the trot should only be for a couple of minutes at a time, building up over the next 2 weeks to a total of 15 minutes, split into two to four periods, depending on the terrain. If the trotting is done in an arena, sharp turns and small circles must be avoided at this stage. Flat work can be incorporated into the routine towards the end of the fourth week; this should be no more than 30 minutes before or after an hour's road work. As the horse gets fitter, lunge work can begin; 20 minutes twice a week is probably enough work on the lunge in side-reins can be very strenuous for young horses and should not be over-used until the horse is fitter. Week 5 or 6: Cantering By now the horse will have been in work for 4 to 6 weeks and cantering can begin. The same principles apply, keeping the horse on the bit, balanced and attentive and only using good going. This initial canter work may be done in a schooling environment where horses often respect their riders more than in an open space. The arena, good ground or an all-weather track are also good places; old parkland is nearly always the best. The horse should be cantered for 2 to 3 minutes at 400 m/min to start with, coming back to walk through trot. These little bouts of canter are built up so that by the end of 2 weeks the horse is cantering for a total of 9 to 10 minutes split into three or four sessions. Always walk the horse for at least 5 minutes after each canter. It is a good idea to enter one or two dressage competitions at this stage; this gives the novice horse a few outings to accustom it to travel, crowds, dressage boards and other monsters! During week 5 or 6, jumping can be introduced into the programme; starting with pole work, grid work and small jumps in the school. This can be incorporated into the schooling programme so that by the end of the second month the Novice horse should have done a small local showjumping class or two.

< previous page

page_205

next page >

< previous page

page_206

next page > Page 206

Weeks 710: Interval Training Interval training may not be everybody's cup of tea, but it is an easy way of getting horses fit with minimal wear and tear and stress. These three things shorten the event horse's career more quickly than anything else. Interval training was originally developed to train middle and long-distance runners and swimmers, and has been used successfully in human athletics for over 20 years. Jack Le Goff (the United States event team trainer) adapted interval training for event horses and supervised its use for three-day event horses in America. This, and the use of interval training by top British event riders including Lucinda Green and Virginia Leng, has led to a great deal of interest in this method of training amongst riders at all levels of the horse trials world. Interval training, like any form of fitness programme, needs careful planning and implementation. It cannot cut corners compared to more traditional training methods, nor can it allow a beginner to train a horse to three-day event fitness from a book. However, if interval training is used along with measurable indicators of fitness, such as pulse, respiration and recovery rates, it does help the less experienced rider get a horse fit, rather than relying on that indefinable quality 'feel', which only comes with years of practice. What Is Interval Training? Interval training consists of giving a horse a period of specific work (canter), followed by a brief interval of semi-rest (walk) during which the horse is allowed to recover partially before being asked to work again. It is a similar principle to getting fit by running between lamp-posts: jog for the distance between two lamp-posts, walk for a little way (until breathing has recovered sufficiently to let one continue comfortably) and run on again, repeating this several times. The Aims of Interval Training A fit event horse is one which has a greater capacity for using oxygen and performing aerobic work; the point at which anaerobic work starts is delayed as much as possible so that the consequent lactic acid build-up is also postponed. As a result the horse is able to work for longer before fatigue sets in (see Fig. 16.1). The periods of work given during interval training develop and extend the horse's capacity for

< previous page

page_206

next page >

< previous page

page_207

next page > Page 207

Fig. 16.1 The effect of training on the anaerobic threshold. intensive work, as the programme progresses, without a build-up of lactic acid. Lactic acid is a major factor contributing to fatigue; the walking periods between canters allow the blood to remove any lactic acid that may be accumulating in the muscle. Interval training increases the horse's tolerance to stress and the measurement of pulse, respiration and recovery rates means that the horse's reaction to the training programme can be closely monitored. Monitoring Interval Training An essential part of the interval training regime is monitoring the horse's temperature, pulse and respiration (TPR). The horse cannot tell the rider how it feels, so the rider must learn to read the signs of stress.

< previous page

page_207

next page >

< previous page

page_208

next page > Page 208

Temperature The horse's normal resting temperature is 38°C (100101°F). Any deviation from normal may indicate stress of some sort, most commonly illness. A clean veterinary thermometer, lightly greased with vaseline, is used to take a horse's rectal temperature (Fig. 16.2). Standing to one side of the hindquarters, lift the tail and gently insert the thermometer into the rectum with a twisting action. Place the thermometer full-length into the rectum, pressing it gently against the wall of the rectum for 1 to 2 minutes, then slowly remove the thermometer with a rotating movement and read. Digital read-out thermometers, although more expensive, are easy to read and make a useful addition to the first aid kit.

Fig. 16.2 Taking a horse's temperature. Pulse The horse's normal resting pulse rate is 3642 beats per minute and corresponds to the heart rate. The easiest place to take the horse's pulse is where the facial artery runs over the cheek bone (Fig. 16.3); run the fingers down the inside of the horse's left cheek bone until you feel a moveable lump, about the diameter of a pencil, running across the bone. Gently press the first two fingers along this lump, cupping

< previous page

page_208

next page >

< previous page

page_209

next page > Page 209

Fig. 16.3 Taking the pulse. the cheek bone, and count the pulse for 10 seconds, then multiply by six to get the pulse rate per minute. A stethoscope can also be used on the left side of the horse, just behind the elbow, in front of the girth (Fig. 16.4). The mounted rider can lean down and press the back of an ungloved hand against the

Fig. 16.4 Using a stethoscope.

< previous page

page_209

next page >

< previous page

page_210

next page > Page 210

horse in front of the girth. Once the horse has had a canter the heart will be clearly felt hammering against the ribs! Respiratory Rate. The horse's normal resting breathing rate how often it breathes in and out is 816 breaths per minute. To take the respiration rate, the in and out motion of the ribs or rise and fall of the flanks is observed (Fig. 16.5). Each combination of in and out is counted as one. The rider can also put a hand close to the horse's nostril and count as the horse breathes out beware the horse does not sniff your hand looking for titbits! In cold weather the horse's breath can be seen as the horse breathes out.

Fig. 16.5 Recording the respiration rate.

< previous page

page_210

next page >

< previous page

page_211

next page > Page 211

To obtain 'normal' values, each of these measurements should be taken while the horse is calm and at rest for example, between feeding and the daily exercise. These values are then used as a baseline against which the values after exercise can be compared. Before Starting Interval training cannot cut corners, and the following factors must be considered before starting a programme: (1) The horse must not be lame and there must be no doubts about its soundness. (2) The horse must be eating well. (3) The horse should be capable of 90 minutes' walk and trot over rolling terrain without distress. The horse which has been conditioned slowly and carefully will stay in peak condition longer than one which has been pushed too fast in the early stages. (4) It is essential to keep a notebook with a running record of the horse's response to work, allowing the programme to be adjusted accordingly. As well as TPR, the weather, type of work and how the horse 'feels' should also be noted. The weather can have a profound effect on how quickly the horse recovers from work during hot and humid weather the horse will continue breathing fast for longer than expected because more rapid breathing is necessary to reduce body heat; so even though the pulse rate may drop to normal, the horse's breathing may still be fast. Pulse is a more reliable gauge of the horse's recovery and how fit it is, and is the most important reading to take. (5) As in any form of training the rider must be alert to any change in the horse's attitude, appetite, coat, droppings, appearance, muscle tone, etc. (6) Interval training may not suit all horses; youngsters may not be mentally or physically ready to cope with a rigorous training schedule. Some excitable horses seem to settle into canter workouts, making them easier to hold when competing, while lazy horses get bored with interval training. (7) The breeding, condition and previous training must also be considered; a stuffy horse may need to work up to a different end-point so that it becomes fitter than the more athletic Thoroughbred-type.

< previous page

page_211

next page >

< previous page

page_212

next page > Page 212

How to Use Interval Training During exercise the horse's pulse and respiration rates increase just as yours do. During interval training the horse is cantered at a predetermined speed for a certain time; after this piece of work the horse is pulled up and the pulse and/or respiration rates recorded immediately, the horse is walked for a set time and the rates recorded again. The difference between the two readings is the 'recovery rate' of the horse. The horse repeats these workouts every 4 days and the pulse and respiration rates are recorded at the same points; as the horse gets fitter, it will recover faster from the work. Fitness is gradually built up by slowly increasing the amount of work the horse is asked to do by increasing the speed and/or length of the workout or by using more demanding terrain. If the recovery rate is not good enough after a workout, the work is adjusted so the horse is never overstressed. The trainer or rider should know the horse and understand its capabilities and limitations, and should be aware of the degree of fitness that is eventually required, so that a flexible programme can be made to suit any horse. This system is markedly different from the more traditional methods where horses are trotted and cantered for long distances, with short sharp gallops postponed till later in the training programme and no repetition of fast work in each workout. The Method In order to carry out interval training correctly, a known distance should be covered in a set time. Ideally, 1600 metres (1 mile) is marked off in 400 metre segments, but if this is not possible a 400 metre gallop will be adequate as long as there are no sharp turns. An easy-to-read wrist stopwatch makes life much easier! The competition for which the horse is being prepared will dictate the speed at which the known distance will be covered, and hence the time allowed to cover that distance. The average speed required to cover 400 metres in 1 minute 49 seconds is 220 m/min, which is the good ongoing trot required for phases A and C (roads and tracks) of a three-day event. This is about 13 km/h (9 m.p.h.). 400 metres in 1 minute is 400 m/min a brisk canter which is a good basis for canter work. 400 metres in 46 seconds is 520 m/min, the Novice cross-country speed.

< previous page

page_212

next page >

< previous page

next page >

page_213

Page 213 400 metres in 35 seconds is 690 m/min, the Advanced three-day event steeplechase speed. It is important for the event rider and the long-distance rider to be able to pace their horse over a given distance and different ground during competition, and interval training helps the rider do this early on in the training programme. It also means that the horse becomes used to travelling at the required speed, which is a useful advantage during competitions. In order to design an effective training programme, the rider needs to know exactly what is required in competition in terms of speed, distance, length and intensity, so that these aspects can be incorporated into the training programme. The Novice event horse has to be able to compete at the distances and speeds shown in Table 16.1. Table 16.1 British Horse Trials Association guide to length and speeds of Novice competitions (1999 Regulations). One-day horse trials Length 16002800 m Speed

520 m/min

Two-day horse trials Phase A

Phase B

Phase C

Phase D

Length 22004400 m

1280 or 1600 m

44007700 m

22003200 m

Speed

640 m/min

220 m/min

520 m/min

220 m/min

Three-day events Phases A and C

Phase B

Phase D

Length 880012100 m

2240 m

39004940 m

Speed

640 m/min

520 m/min

220 m/min

Interval training in trot can be incorporated in week 3 or 4 of the fitness programme, helping to accustom both horse and rider to a 220 m/min trot. An average horse trots at about 200 m/min and may need to trot more briskly to cover 400 metres in 1 minute 49 seconds. In the first session, two 400 metre trots with a 3 minute walk between would be sufficient. After the second trot the horse's pulse and respiration are recorded and checked again after 10 minutes of walking to make sure that the horse has not been overstressed. After this break the horse's pulse and respiration should have returned to normal if they have not, the horse is not fit enough and should stay at this level of trot work the next day. If the horse has responded well, a further 400 metre trot can be added after a 3

< previous page

page_213

next page >

< previous page

page_214

next page > Page 214

minute walk. Now that the feel of a 220 m/min trot has become well established, the trotting sessions can be governed by the time rather than distance and gradually the length of time spent trotting can be increased, building up over the next couple of weeks to 15 minutes in total, split into five 3 minute periods. This work at trot is invaluable for introducing the newcomer to interval training, developing a feel for speed and distance, practising taking pulse and respiration rates and keeping the necessary records: speed, time and number of repetitions. Remember that the horse should walk for at least 15 minutes before doing any trot work. The horse's pulse and respiration values will rarely return to the resting values obtained in the stable due to excitement and the fact that it is recovering in walk, so a value for the horse's warmed-up pulse and respiration should be obtained and used as baseline values. A horse walking actively will have a heart rate of between 60 and 70 beats per minute. Interval Training in Canter By the end of week 6 the horse will have been cantering for at least 1 week and interval training can now start in earnest. If the rider is not used to interval training, it is best to start the programme very gradually; after an initial 20 minute warm-up period of walking and trotting, the measured 400 m distance should be cantered in 1 minute (400 m/min). This is followed by 3 minutes of walking and another 1 minute canter, after which the pulse and respiration rates are recorded. If after 10 minutes of walking the pulse has returned to normal, the horse can work harder in its next canter session, 4 days later. During the next canter workout the horse can be cantered for 3 minutes at 400 m/min; this is followed by 1 minute in trot and a recovery period in walk of 3 to 5 minutes. This is repeated twice, after which the horse is cooled down in walk for at least 20 minutes. The heart rate should be no more than 180 beats per minute (b.p.m.) at the end of each canter and no more than 100 b.p.m. before the next canter commences. If the heart rate takes more than 5 minutes to drop below 100 b.p.m., then either the canter was too long, the terrain too steep, the speed too fast or the initial work has not been carried out correctly. Canter work is repeated every fourth day, building the sessions up minute by minute. The day after a canter session should be a rest or just a hack for 1.5 to 2 hours. Over the next 2 weeks the sessions are built up so that the horse can do three lots of 5 minute canters at

< previous page

page_214

next page >

< previous page

page_215

next page > Page 215

400 m/min, with 3 minutes of walking in between as shown in Table 16.4 (see later in this chapter). Once interval training starts the horse's work should fit into a 4 day regime. For example: Day 1: Hack only or rest day. Day 2: Hack 60 minutes. Schooling 40 minutes. Day 3: Hack 60 minutes. Schooling and jumping 45 minutes. Day 4: Hack 45 minutes. Canter session. It is wise to replace front brushing boots with tendon support boots for canter work and jump training to avoid injury caused by the horse striking into its front legs from behind. Over-reach boots are a personal choice but, if used, make sure they are not floppy, otherwise there will be a risk that the horse will tread on them with its hind feet. The heavier shoes used for road work will by now have been replaced by lighter ones, fitted with stud holes ready for future events. Swimming can replace some of the canter work and may help keep the horse sweeter. Swimming can persuade stuffy and lazy horses to do more work. This type of horse can lose enthusiasm for fast work after a while, even if they are worked upside other horses. Swimming can persuade them to do more work. Always go to an expert before swimming horses. Initially, swimming can be quite stressful so horses should only do a little to start, but as they become accustomed to swimming it actually helps them relax and wind down. The horse should always be walked after it has swum. By now the horse will have been in about 10 weeks; road work continues each day with 45 minutes on canter days and 1.5 to 2 hours on hack-only days. Weeks 1012: The Final 2 Weeks The first Horse Trial can be planned for week 12; in the final 2 weeks the road work, schooling and jump training continues as usual. After a couple of these work sessions, the last minute of the last canter can be increased to a speed of 500 m/min. The canter work is shown in Table 16.2. The heart rate after the third canter should drop below 100 b.p.m. after 10 minutes of walking. The idea of interval training is to allow the horse to work aerobically for longer periods. However, at some stage during the cross-country or steeplechase the horse will work anaerobically. Increasing the speed at the end of the last two canter sessions makes the horse work anaerobically; the trotting afterwards

< previous page

page_215

next page >

< previous page

page_216

next page > Page 216

Table 16.2 Interval training to Novice one-day event fitness. 20 minutes' warm-up Canter 1:

5 minutes @ 400 m/min Trot 30 seconds Walk 3 minutes

Canter 2:

4 minutes @ 400 m/min 1 minute @ 500 m/min Trot 30 seconds to 1 minute Walk 3 minutes

Canter 3:

4 minutes @ 400 m/min 1 minute @ 500 m/min building up to 550 m/min Trot 1 to 2 minutes Walk at least 20 minutes

helps disperse the lactic acid and thus the heart rate recovers more quickly. Seven to ten days before the competition, take the horse cross-country schooling or to a Hunter Trials, weather permitting; this will replace a work day. It cannot be emphasised enough that all horses are individuals and must be treated as such; tables are merely a guide and do not allow for lost shoes, heavy going or lazy horses. The real skill in training lies in the ability to design programmes for individual horses and to recognise the need to adapt the programme without hindering the horse's progress. The same programme may take up to 2 weeks longer with a different horse. This sort of training should not be carried out more than twice a week and if a horse is experiencing difficulty there are several factors that can be changed to suit the individual. distance of each canter speed interval between canters the number of canters. It must also be remembered that the training area will vary as the weather varies and the rider must be prepared to alter the canter programme to allow for this. Competing in Horse Trials Ideally horses run on alternate weekends. If this is not possible they should do no more than three Horse Trials on consecutive weekends.

< previous page

page_216

next page >

< previous page

page_217

next page > Page 217

After each competition the horse should have a day off, followed by an easy day. If it is running on consecutive weekends the horse should do a shorter piece of work 4 days after the last competition. Two 4 minute canters at 400 m/min, with a 3 minute walk between is probably enough. The aim of competing with a young horse should be to ride a calm, accurate dressage test and to go showjumping and cross-country with no jumping penalties. The horse must be given time to see and understand the cross-country fences and be happy in its work; once this is accomplished the speed can be stepped up to avoid getting time penalties. The rider of the young horse who blazes around may have gone fast enough to win, but they may have spoilt a good young horse in the process. The object of the horse's first event, and indeed the first few events, is to teach the horse about its job the early events should be considered part of the training process. It is important to allow enough time between competitions to iron out any problems that may have arisen with the young horse during competition. After about 3 months of competition it is a good idea to give the young horse a short break and let it down a little; this will stop it getting sour or jaded, and may coincide with mid-summer when the ground is at its hardest. The length of this mini-holiday will vary from horse to horse: 2 weeks out at grass by day and in at night with perhaps 20 minutes a day lungeing may be enough. After this break the horse should have 2 weeks' training and schooling before competing again. By now the rider should be aiming to get placed in competition, depending on how the horse is progressing. After another 3 months of competition the horse should be roughed off for 2 months' rest or partial rest. It is important to corn-feed the horse during this period so that it does not lose condition. The Novice's eventing year will therefore look like this, depending on the events for which it is entered:

January to March:

getting fit

April to June:

competing

early July:

rest

late July:

regaining fitness

August to October

competing

November/December

roughed off

< previous page

page_217

next page >

< previous page

page_218

next page > Page 218

Interval Training to Advanced Levels The demands made upon horses competing in three-day events, National Hunt racing and point-to-pointing require that the horse is at peak physical fitness and condition. The rider and trainer must be aware of the rigorous task for which they are training the horse. On the cross-country day the horse will be required to complete the following four phases, consisting of: Phases A and C: Roads and Tracks Between 15,400 m to 18,700 m (9.5 to 11.5 miles) to be covered at a speed of 220 m/min. This is a good working trot or mixture of walk and canter, aiming to cover 1 kilometre in 4 minutes, a total of 70 to 85 minutes of endurancetype work. Phase B: Steeplechase. Either 3105 m or 3450 m (2 miles) to be covered in either 4.5 or 5 minutes at a speed of 690 m/min. This is a fast gallop and the horse must be taught to jump safely at speed; if he is pushed out of his natural galloping stride he may fall or become tired during this phase. Phase D: Cross-Country Between 6840 m and 7980 m (4 to 5 miles) to be covered at 570 m/min in a time of between 12 and 14 minutes. This is a fairly fast gallop including up to 45 jumping efforts over solid and imposing obstacles. (Taken from the British Horse Trials Association Rule Book 1999, for four star three-day events such as Badminton or Burghley.) The aim of the training programme is for the horse to complete this severe test at the required speed without fatigue in the latter stages which could lead to a silly mistake and a fall. The horse must also be fit enough to pass the veterinary inspection the next day and to showjump accurately. The horse trained to Advanced one-day event fitness (Table 16.3) should be able to work aerobically during canters of up to 550 m/min. Cantering for longer times does not actually increase the horse's ability to cope with the demands of the faster speeds in Advanced horse trials and three-day events. This means that the speed and/or hill work must be used to train horses at these levels; this is particularly true for part-bred horses. Before a rider attempts to get a horse to this level of fitness, they need to know the horse intimately and have a thorough knowledge of its requirements, capabilities and limitations. The breeding or type of horse, its present condition and previous fitness must all be considered when devising this horse's training programme.

< previous page

page_218

next page >

< previous page

page_219

next page > Page 219

Table 16.3 Interval training to Advanced one-day event fitness. 20 minutes' warm-up Canter 1:

6 minutes @ 450 m/min Trot 30 seconds Walk 3 minutes

Canter 2:

4 minutes @ 450 m/min 2 minutes @ 550 m/min Trot 30 seconds to 1 minute Walk 3 minutes

Canter 3:

4 minutes @ 450 m/min. 2 minutes @ 550 m/min building up to 650 m/min Trot 1 to 2 minutes Walk at least 20 minutes

It is generally accepted that it takes 4 months to get a horse from soft condition to three-day event fitness. The task is made much easier if the following points are considered: the horse must be fed concentrates whilst at grass if the weather is unpleasant or the ground wet, the horse should be stabled at night the break should not be too long 2 months is enough to rest the horse without losing too much fitness if the horse has not been brought to this level of fitness before, as much as 4 weeks may have to be added to the training programme. The first 6 weeks would be much as outlined for the Novice horse. The next 4 to 6 weeks would see the work being stepped up to get the horse fit for an Advanced one-day event, as shown in Table 16.3. For the 4 to 6 weeks before a four star three-day event such as Badminton or Burghley, the speed and length of the fast work would be gradually increased so that the last minute is performed at steeplechase speed (690 m/min), preparing the horse to go the required distance at that speed. The length of the gallop is thus kept down to 690 metres (less than half a mile) so that the horse is not overstressed but the body systems are primed to cope with anaerobic work. The final levels to which riders work up will vary. For example: Three repetitions of 9 minute canters at 550 m/min, 2 minutes of walking between each, with the last minute of the final two canters at 690 m/min.

< previous page

page_219

next page >

< previous page

page_220

next page > Page 220

Three repetitions of 10 minute canters at 550 m/min, 3 minutes of walking between each, with one full-speed 800 metre gallop at the end. Three repetitions of 12 minute canters at 500 m/min, 3 minutes' walking between, last minute of last canter at 690 m/min. Some riders believe that three repetitions of 8 minute canters are adequate and that increasing to 10 minutes does not significantly increase fitness, providing the canters are fast enough. The short sprints develop speed and strength, while the long slower canters develop rhythm and staying power. During racing and three-day eventing maximum muscle contraction is demanded and lactic acid will accumulate in the muscles. The horse's body must learn to cope with and dissipate these high lactate levels so it is important that these levels of exercise are experienced in training hence the importance of the short gallop at the end of the canter workout. Points to Remember Interval training must be monitored by pulse and respiration rate, not by time alone. It is the pulse rate immediately after the work that shows how much stress to which the horse has been subjected, and the recovery rate that shows how fit the horse is. Without these records interval training is meaningless and can actually be harmful. If the horse is required to work anaerobically the pulse rate should exceed 200 beats per minute; this can be estimated by looking at the pulse 1 minute after pulling up. If the horse has been beneficially stressed its pulse will lie between 120 and 150 beats per minute 1 minute after stopping work. If its pulse exceeds 150 b.p.m. it has been overstressed; if below 120 b.p.m. it has not worked hard enough. This guide should only be used well on into the programme, or the horse may be overworked. If the pulse and respiration have not returned to normal within 20 minutes of completing the workout the horse has been overworked and the programme should be adapted accordingly. The respiration rate should not exceed the pulse rate; if it does, stop work and ask what has caused this lack of fitness, environmental conditions, or a problem with the horse's respiratory tract? Never finish the work if the horse is distressed gasping, blowing excessively, stumbling, changing legs frequently and reluctant to continue.

< previous page

page_220

next page >

< previous page

page_221

next page > Page 221

However, the horse must be stressed enough to stimulate the body systems to become better adapted to exercise. The heart rate must be raised above 100 b.p.m. after work. It is possible to over-train horses; if the horse is getting too fit too quickly, increase the distance of the canter rather than the speed. Long slow work for a couple of sessions will maintain fitness without exciting the horse. The programme should be planned backwards from the proposed event(s) so that work days fall into appropriate places before competition. The horse may become bored, so vary the work by cantering in different places or taking it swimming. Swimming is useful in maintaining aerobic capacity, particularly after minor lower limb injuries. Always warm up and cool down thoroughly before cantering, particularly if the horse has to travel in a lorry or trailer to the work area. Stable Management Tips After each workout hose the horse's legs for 5 minutes and apply a cooling lotion or gel to help get rid of any heat caused by the work. After the cross-country either apply a cooling lotion or poultice and bandage the horse's legs overnight. Always check the horse's legs at least twice a day and get to know their normal temperature and lumps and bumps. As horses get fitter they tend to eat less hay and will only eat a certain amount of concentrates. Feed to just below appetite so that they are always keen for their next meal. Make sure they have the best quality feed and that any changes to the diet are made gradually. If in doubt, hay should be soaked or a dust-free alternative used. Shavings or paper make good alternatives to straw. A sports therapist can keep an eye on the stress imposed on the musculoskeletal system. If the muscles are doing their job properly there is less chance of tendons and ligaments becoming damaged.

< previous page

page_221

next page >

< previous page

page_222

next page > Page 222

Table 16.4 Interval training to Novice one-day event fitness: a detailed 12-week schedule. Throughout the programme the horse will be turned out for a couple of hours whenever possible. Week 1 Day 1: 20 minute walk. Day 2: 30 minute walk. Day 3: 40 minute walk. Day 4: 50 minute walk. Day 5: 60 minute walk. Day 6: 60 minute walk. Day 7: Rest day. Week 2 Day 1: 1 hour 10 minute walk. Day 2: 1 hour 20 minute walk. Day 3: 1 hour 30 minute walk. Day 4: 1 hour 40 minute walk. Day 5: 1 hour 50 minute walk. Day 6: 2 hour walk. Day 7: Rest day. Week 3 Day 1: 2 hour hack including one 400 m (1 minute 49 seconds) trot. Day 2: 2 hour hack including two 400 m trots. Day 3: 2 hour hack including three 400 m trots. Day 4: 1 hour 30 minute hack including two 800 m (3 minute 38 seconds) trots. Day 5: 1 hour 30 minute hack including three 800 m trots. Check recovery. Day 6: 1 hour 15 minute hack including two 1100 m (5 minute) trots. Day 7: Rest day. Week 4 Day 1: 1 hour 30 minute hack including three 5 minute trots. Check recovery. Day 2: as Day 1. Day 3: 60 minute walk plus 20 minutes of schooling. Day 4: as Day 1. Day 5: 60 minute walk plus 20 minutes of schooling. Day 6: as Day 1. Day 7: Rest day. (table continued on next page)

< previous page

page_222

next page >

< previous page

page_223

next page > Page 223

(table continued from previous page) Table 16.4 Interval training to Novice one-day event fitness: a detailed 12-week schedule. Week 5 Day 1: 1 hour 30 minute hack including three 5 minute trots and one 1 minute canter (400 m at 400 m/min). Check recovery. The canter work may be done in the school. Day 2: 60 minute walk plus 20 minutes of schooling, including pole work. Day 3: 60 minute walk plus 30 minutes of schooling. Day 4: 1 hour 30 minute hack including three 5 minute trots and two 1 minute canters. Check recovery. Day 5: 60 minute walk plus 30 minutes of schooling, including small jumps. Day 6: 1 hour 30 minute hack including three 5 minute trots and three 1 minute canters. Check recovery. Or dressage competition. Day 7: Rest day. Week 6 Day 1: 1 hour 30 minute hack including three 5 minute trots and two 2 minute canters (800 m at 400 m/min). Check recovery. Day 2: 60 minute walk plus 40 minutes of schooling, including pole work. Day 3: 60 minute walk plus 40 minutes of schooling, including small jumps. Day 4: 1 hour 30 minute hack including three 5 minute trots and three 2 minute canters. Check recovery. Day 5: 60 minute walk plus 40 minutes of schooling. Day 6: 1 hour 30 minute hack including three 5 minute trots and two 3 minute canters (1200 m at 400 m/min.). Check recovery. Or small showjumping competition. Day 7: Rest day. Week 7 Interval training begins in earnest and the 4-day schedule is adhered to as far as possible Day 1: Hack. Day 2: 60 minute hack plus 40 minutes of schooling. Day 3: 60 minute hack plus 45 minutes of schooling and jumping. Day 4: 45 minute hack plus three 3 minute canters at 400 m/min with 3 minute walk between. Check recovery. Day 5: Hack. Day 6: 60 minute hack plus 40 minutes of schooling. Day 7: Dressage or showjumping competition. (table continued on next page)

< previous page

page_223

next page >

< previous page

page_224

next page > Page 224

(table continued from previous page) Table 16.4 Interval training to Novice one-day event fitness: a detailed 12-week schedule. Week 8 Day 1: 45 minute hack plus one 3 minute canter and two 4 minute canters at 400 m/min with 3 minute walk between. Check recovery. Day 2: Rest day. Day 3: 60 minute hack plus 40 minutes of schooling. Day 4: 60 minute hack plus 45 minutes of schooling and jumping. Day 5: 45 minute hack plus three 4 minute canters at 400 m/min, with 3 minute walk between. Check recovery. Day 6: Hack. Day 7: 60 minute hack plus 40 minutes of schooling. Week 9 Day 1: 60 minute hack plus 45 minutes of schooling and jumping. Day 2: 45 minute hack plus two 4 minute canters and one 5 minute canter at 400 m/min, with 3 minute walk between. Check recovery. Day 3: Rest day. Day 4: 60 minute hack plus 40 minutes of schooling. Day 5: 60 minute hack plus 45 minutes of schooling and jumping. Day 6: 45 minute hack plus one 4 minute canter and two 5 minute canters at 400 m/min, with 3 minute walk between. Check recovery. Day 7: Hack. Week 10 Day 1: 60 minute hack plus 40 minutes of schooling. Day 2: 60 minute hack plus 45 minutes of schooling and jumping. Day 3: 45 minute hack plus three 5 minute canters at 400 m/min, with 3 minute walk between. Check recovery. Day 4: Rest day. Day 5: 60 minute hack plus 40 minutes of schooling. Day 6: 60 minute hack plus 45 minutes of schooling and jumping. Day 7: Cross-country schooling to replace canter work. Week 11 Day 1: Hack. Day 2: 60 minute hack plus 40 minutes of schooling. Day 3: 60 minute hack plus 45 minutes of schooling and jumping. Day 4: 45 minute hack plus one 5 minute canter at 400 m/min, two 4 minute canters at 400 m/min finishing with 1 minute at 500 m/min, with 3 minute walk between. Check recovery. Day 5: Rest day.

Day 6: 60 minute hack plus 40 minutes of schooling. Day 7: 60 minute hack plus 45 minutes of schooling and jumping. (table continued on next page)

< previous page

page_224

next page >

< previous page

page_225

next page > Page 225

(table continued from previous page) Table 16.4 Interval training to Novice one-day event fitness: a detailed 12-week schedule. Week 12 Day 1: 45 minute hack plus 5 minutes at 400 m/min, 4 minutes at 400 m/min plus 1 minute at 500 m/min, 4 minutes at 400 m/min plus 1 minute at 550 m/min, with 3 minute walk between. Check recovery. Day 2: Hack. Day 3: 60 minute hack plus 40 minutes of schooling. Day 4: 60 minute hack plus 45 minutes of schooling and jumping. Day 6: FIRST HORSE TRIALS. Day 7: Rest day.

Traditional Methods These methods involve long distances of relatively slow galloping to develop the horse's muscles, lungs and heart. A horse at 1-day fitness would be completing an 800 to 1200 metre (0.5 to 0.75 miles) gallop at half-speed once a week. This would be gradually increased to 1200 metres (0.75 miles) at half-speed plus 800 metres (0.5 miles) at three-quarter speed, and then to 1600 metres (1 mile) at half-speed plus 1600 metres (one mile) at three-quarter speed by the end of week 13. Prior to a three-day event, the horse should be able to gallop for 3000 metres (2 miles), starting at 550 m/min and finishing fast and on the bit. The second piece of fast work to be completed during a week's programme would be longer and slower, a canter at about 400 m/min would be built up over the 4 weeks prior to the competition to 20 minutes of sustained work.

< previous page

page_225

next page >

< previous page

page_226

next page > Page 226

17 Fitness for Other Disciplines Training the Long-Distance Horse Long-distance and endurance riding can cause severe distress in a horse that has not been properly prepared. Riders must be capable of training a horse to a very high level of fitness brought about by following a carefully prepared schedule of regular exercise. There are no short cuts when getting to this degree of fitness. The rider, too, must be fit, as a tired rider hinders the horse. The rider must also be able to recognise subtle signs of stress in the horse and be able to take suitable action to prevent any further distress. The long-distance horse can suffer from muscular, cardiovascular and metabolic stress. Muscular stress is seen when a tired horse starts to flag and stumble, and muscle tremors may be seen in flank and thigh. The pace should be steadied or the horse will become exhausted. Cardiovascular stress can be monitored by checking pulse and respiration rates. Indeed, long-distance riders must be very aware of pulse and respiration rates as horses are not allowed to continue until these values are considered suitable by the vet in charge. The normal ratio of pulse to respiration is between 2:1 and 3:1. If the cardiovascular system is stressed the respiration rate may increase dramatically, equalling that of the heart. A heart rate to breathing ratio of less than 2:1 is serious and the horse must be rested immediately. Metabolic stress may manifest itself as heat stroke, dehydration, tying-up or colic, which have been discussed previously. The Training Programme The routine will vary according to the type of event entered. A hunting-fit horse would be able to complete a short ride of 30 km (20 miles) with no ill effects, but the hunter is not conditioned to maintain a steady pace for prolonged distances.

< previous page

page_226

next page >

< previous page

page_227

next page > Page 227

Assuming that the horse is sufficiently fit for light hacking, the following time should be allowed to get the horse fit for different events: Plus 2 weeks

30 km (20 mile) pleasure ride

Plus 4 weeks

50 km (30 miles) at 9 km/h (6 m.p.h.)

Plus 8 weeks

65 km (40 miles) at 10 to 11 km/h (6.5 to 7 m.p.h.)

Plus 3 months

80 km (50 mile) endurance ride

Plus 4 months

Bronze or Silver Golden Horseshoe ride

Plus 4 1/2 months

120 km (75 mile) ride/Gold in Golden Horseshoe ride

Plus 5 months

160 km (100 mile) ride

The long-distance horse will benefit from a longer period of slow conditioning work than, for instance, the hunter. Some trainers advocate a 2 month period of walking and trotting work, beginning with 1 hour per day building up to 3 hours per day. Cantering work is introduced only when stamina and muscle strength are well developed. Many riders who participate in long-distance events do not have 3 hours a day to devote to exercising their horses. While it is preferable to exercise every day, it is perfectly feasible to get a horse fit riding it every other day, provided longer rides are given at weekends and the horse is got out for some exercise daily. The horse should be ridden over varied terrain. This helps prevent it from becoming bored and also helps build up muscle. However, hills are not necessary for getting a horse fit provided adequate time and distance is put in. The horse must be made to work during these rides this will help to develop its paces. If the horse has a natural slow, short-striding walk, this should be improved until the horse is able to average a 6 to 8 km/h (4 to 5 m.p.h.) walk. During a ride the horse must be relaxed in walk because it is the pace used for recovering and 'resting'. The rider must aim for a long, free-striding walk on a light contact, with the horse calmly picking its way over the ground. In actual competition, trot is mainly used. It is a pace that covers the ground, spreads the workload evenly, and is thus less tiring for the horse. The rider must remember to change the diagonal frequently. Again, the trot must be encouraged to be long-striding and easy; a good, strong trot will average 14 to 16 km/h (9 to 10 m.p.h.), a slow trot about 9 to 11 km/h (6 to 7 m.p.h.). Each horse has a speed within a pace at which it is happiest working, and forcing a horse to go faster is tiring for both horse and rider. If a horse has a naturally slow trot that has not been improved by training, it should not be hurried and instead time should be made up by cantering.

< previous page

page_227

next page >

< previous page

page_228

next page > Page 228

A rolling canter averages about 16 to 19 km/h (10 to 12 m.p.h.). It is a useful pace in endurance rides where the horse needs to maintain canter for long distances, developing a machine-like rhythm. Two different types of work can be used side by side in the training programme: shorter, sharper rides to develop the horse's wind longer, steadier rides to develop stamina and the steady, rhythmic paces necessary for successful competition. The lengths and speeds of rides during training will vary depending on the competition goal, and will be outlined in more detail later. In long-distance work, almost more than any other equestrian sport, it is essential for the rider to know the horse. It is not a sport where one person can train a horse and another person successfully compete on it. Where horse and rider are a team, there is a greater likelihood of success. Pulse and Respiration Rate Long-distance rides are subject to stringent veterinary checks, and pulse and respiration are among the checks made. This has resulted in the rider being very aware of their horse's pulse and respiration rates, using them as a guide of fitness during training and competition. The following points are useful to remember: (1) Establish normal resting values. (2) Establish unfit working values. Find a hill or convenient stopping point on one of the exercise routes, and record the rates after the horse has walked to the top. Walk on quietly for 10 minutes, and take them again. Take pulse and respiration rates at the same place each week, noting speed, climate and any other factors that might affect the horse's pulse and respiration. (3) As the horse gets fitter, the initial readings will get lower and the horse will have recovered in the 10 minute interval. This indicates that the horse is ready for more strenuous work. As a rough guide, the horse can begin to work harder if the pulse is below 80 beats per minute after a work session. Allow the pulse to drop to about 60 before continuing work. (4) The horse's pulse and respiration should have returned to normal within 30 minutes of finishing work. If, during a competition, the pulse has not fallen to below 70 after a compulsory rest period, the horse may not be allowed to continue.

< previous page

page_228

next page >

< previous page

page_229

next page > Page 229

Pleasure Rides. These are rides of 30 to 50 km (20 to 30 miles) length, performed at speeds of 8 to 10 km/h (5 to 6 m.p.h.). A horse that is hunting fit would be able to complete one of these rides with no ill effects. A horse that was hacking 10 to 16 km (6 to 10 miles), four times a week, would be adequately fit for a 30 km (20 mile) ride. A 50 km (30 mile) ride would require longer training rides including several miles of trotting at 13 km/h (8 m.p.h.) and canter work. It would take about 4 weeks to get a horse from light hacking fitness to 50 km at 10 km/h (30 miles at 6 m.p.h.) fitness. The general routine would involve 3 days of ordinary exercise and 2 days with longer rides. The horse could be given sharp canters of about 1.5 km (1 mile) during the shorter rides, but the average speed of a ride should not be more than 16 to 20 km/h (10 to 12 m.p.h.) because this imposes too much stress on the horse. A week's exercise may be along the following lines: Monday: 9 km (6 miles) in 1 hour at a steady pace. Tuesday: Semi-rest day; light exercise or turned out to grass. Wednesday: 90 minutes at 10 km/h (6.5 m.p.h.). Thursday: 2 hours including 3 km (2 miles) canter-work. Friday: Semi-rest day. Saturday: 3 hours at 8 km/h (5 m.p.h.). Sunday: 30 to 35 km (20 to 25 miles) at a steady pace. This routine makes best use of the weekends, so that the rider who works full-time is still able to get their horse fit. On semi-rest days the horse is usually turned out in the field, depending on the time of year and the weather. Lunge work can be substituted for 20 to 30 minutes of the ridden work, provided the horse is lunged correctly. Competitive Trail Rides (CTRs) The rides vary in severity from 40 km (25 miles) in 1 day, through about 95 km (60 miles) in 2 days, to 160 km (100 miles) in 3 days, and are judged on a 'time plus condition' basis. There is an optimum time, with penalties given for any loss in condition of the horse. An extra 4 weeks should be allowed to get a horse from 50 km (30 miles) in 1 day to 65 km (40 miles) in 1 day fitness. The speed is usually about 10 to 11 km/h (6.5 to 7 m.p.h.) and only a fit horse can do this without stress. The horse must work 6 days a week over greater distance and at faster speeds. The programme for the last 4 weeks before a 65 km (40 mile) competitive trail ride at 11 km/h (7 m.p.h.) could be as follows:

< previous page

page_229

next page >

< previous page

page_230

next page > Page 230

Week 1 Monday: 1.5 hours at 10 km/h (6.5 m.p.h.). Tuesday: 1.5 hours at 10 km/h (6.5 m.p.h.). Wednesday: 1 hour at 16 km/h (10 m.p.h.). Thursday: 2.5 hours at 9 to 10 km/h (6 m.p.h.). Friday: 30 to 40 km at 9 to 10 km/h (20 to 25 miles at 6 m.p.h.). Saturday: 1.5 hours' easy ride. Sunday: Rest day. Week 2 All distances increased by 3 to 5 km (2 to 3 miles). Friday: 40 km at 11 km/h (25 miles at 7 m.p.h.). Week 3 Three consecutive workdays consisting of one ride of 40 km at 11 km/h (25 miles at 7 m.p.h.) and two rides of 30 km at 11 km/h (20 miles at 7 m.p.h.) Two days of light hacking and 2 days of walking work. Week 4 The horse is just kept ticking over before the ride with a 30 km (20 mile) ride in 2.5 hours in the middle of the week. To compete at this level is very time consuming, as the rider must be prepared to have a horse capable of doing more than the stipulated minimum requirement. The ultimate aim is to compete in 160 km (100 mile) competitions, such as the Golden Horseshoe Ride. The horse must have a thorough programme of slow work as a broad base on which to build this sort of fitness. The horse must also be used to carrying the rider's weight for a long time. Another 4 weeks should be allowed before a horse would be expected to complete a Golden Horseshoe Ride with a Bronze or Silver award. Yet another 2 weeks should be added to this before a horse could be expected to gain a Gold award. Endurance Rides These rides vary in length from 80 to 160 km (50 to 100 miles) and the fastest fit horse wins. This means that the emphasis is on accelerated performance for long periods, so the training programme has to be conducted at greater consistent speed. It cannot be overemphasised that to keep a horse sound under this degree of stress there must be a firm basis of long slow work. In order to be up with the leaders in an 80 km (50 mile) endurance

< previous page

page_230

next page >

< previous page

page_231

next page > Page 231

ride, the horse must average 16 km/h (10 m.p.h.). The initial training is similar to that for a competitive trail ride, but the last 4 weeks concentrate at higher speeds, e.g. 30 to 40 km rides at 16 km/h (20 to 25 miles at 10 m.p.h). Endurance rides of 120 or 160 km (75 or 100 miles) are very tough, and absolute fitness is vital. The horse will average 13 km/h (8 m.p.h) and be under saddle for 12 to 20 hours. The lead-up to these rides should include at least two 80 to 95 km (50 to 60 mile) rides. This not only increases the horse's fitness but allows the rider to establish the horse's individual pattern for the ride. Interval Training for Long-Distance Riding It may appear to be a contradiction in terms to use interval training for long-distance riding, but a certain amount of fast work does have a role to play. The long-distance horse needs a high proportion of slow twitch muscle fibres; these have a high ability to use oxygen, and fatigue slowly. Arabs have an inherently high proportion of slow twitch fibres and excel at endurance work. However, the horse is born with a certain proportion of slow twitch to fast twitch fibre, and this is not changed with training. What training can accomplish is to develop the aerobic capacity of the fast twitch fibres. Training increases the proportion of fast twitch high-oxidative fibres; thus the endurance ability of the horse is enhanced. This is done by increasing the anaerobic threshold (the point where lactic acid build-up begins) by including faster work in the training programme. Interval training for 30 to 45 minutes twice a week, getting the heart rate up to 160 beats per minute for a short time without overstressing the horse, will increase the aerobic capacity of the muscles. This fast work has the added advantage of stimulating the cardiovascular and respiratory systems (heart and wind). Long, slow work has little effect on these systems but does serve to build up muscle, increase resistance to fatigue and develop the glycogen sparing effect, and it also accustoms the horse to carrying the rider's weight. Interval training has been used very successfully to train long-distance horses. Six to eight weeks of walk and trot are essential before canter-work begins. Intervals of slow canter can then be introduced, building up to three 12 minute canter intervals with 3 minutes' walking in between, in the last month before, for example, the Golden Horseshoe Ride. The slow long-distance work is given on the other days of the week, as outlined previously. Pleasure rides and qualifying rides act as a very important part of

< previous page

page_231

next page >

< previous page

page_232

next page > Page 232

the fitness programme. They offer a guide to fitness, but they also ensure that the rider is achieving the required speeds this is particularly useful for the rider training alone. Long-distance riding has become more popular recently. Many of those participating originally bought a horse to hack, then decided to compete in distance rides and found the discipline and skill needed to get a horse fit, the degree of competitiveness and the companionship developed between horse and rider, very fulfilling. Long-distance riding does, however, demand fitness from horse and rider, and should only be undertaken if the horse is adequately prepared. Training the Dressage Horse The dressage horse is the ultimate specialist, and its training does not rely on fitness so much as the ability to perform certain movements with ease, elegance and accuracy. That is not to say that the dressage horse does not have to be fit; indeed, to compete throughout a long season of indoor and outdoor shows, the horse must be in top condition. This involves mental as well as physical condition, and the dressage horse must possess the correct attitude to its work; it must accept discipline and not 'boil' under pressure. The dressage rider trains the horse to make it more gymnastic and athletic, and to help develop its natural ability so that it is able to work with increasing ease, balance and elegance. Key words for successful dressage are suppleness, power and control. During training, the horse becomes more collected; its centre of gravity moves backwards and the hind legs become increasingly engaged. At the same time, the horse develops muscle tone and power; the top line becomes more exaggerated, with a crested neck and well developed hindquarters. However, the heart and lungs are not extended to the same degree as in a horse that is required to gallop. Muscle development takes, quite literally, years of work to acquire, but is easily lost if the horse is not in work. Several weeks of not being ridden would require months of work to regain lost muscle tone. This means that the working year of the specialist dressage horse is unlike that of other competition horses in that it is not roughed-off and turned away for a long rest. Instead, it is given two or three short breaks, of no more than 2 to 3 weeks, during the year. During this break, the horse would probably be turned out by day and brought in at night and corn-fed. This freshens the horse up without it losing too much muscle. If, for some reason, the horse has been out of work for more than 4

< previous page

page_232

next page >

< previous page

page_233

next page > Page 233

or 5 weeks, it should be walked and trotted on roads and tracks for 2 to 3 weeks before dressage training starts again. Theoretically, the type of fitness required for a dressage horse can be achieved entirely by working in the school. However, great care must be taken not to strain muscles through overworking the horse in a confined space before a correct degree of muscle tone has been established. Road work should nevertheless be active, with the horse working in the correct outline for short periods during the hack. Once the horse is fit, it can be schooled or lunged for up to 40 minutes per day, but sessions of collected work must always be interspersed with work on a loose rein so that the horse is able to relax and rest muscles that may be tired from unaccustomed exertion. The training programme must be varied to prevent the horse from becoming sour or tense. Quiet hacking on the road before, after or instead of schooling will help the horse to relax. Loose jumping and gymnastic jumping exercises will encourage the horse to use itself and keep supple. A canter in a suitable field to improve the heart and wind will also give the horse a break from the demands of collected work. The dressage horse is improved by systematic intensive work, and year by year the horse advances until it has reached the limits of its performance. During the first year of the horse's training, it is taught to move forwards freely on the lunge and under a rider. Lateral work is taught in the second year, and the horse progresses to flying changes, greater collection and better extension during the third year of training. Thus, provided the horse, rider and trainer have the ability, the horse could be working on piaffe and passage in its fourth year of training, i.e. as an 8-year-old. Actually getting the dressage horse fit is one thing, but long-term success depends on correct, careful and skilled training. Training the Showjumping Horse Showjumping is a specialist sport, and much of the fitness programme consists of schooling the horse and improving its jumping technique. Training and fitness go together; thus the training programme will vary according to the age and ability of the horse, and how much of the year the horse is competing. Very little change is made to the natural shape of the showjumping horse. There is muscle development, but this is not as pronounced as in the dressage horse. Fitness and stamina are improved, but not to the same extent as in the event horse. Possibly the greatest change made to

< previous page

page_233

next page >

< previous page

page_234

next page > Page 234

the showjumper is in its movement, particularly the canter which becomes more powerful, balanced and responsive. The aim of training is to enable the horse to make the best use of its natural ability to jump high and clean. The trainer does this by using basic flat work to develop balance and collection, encouraging the horse to have a rhythmic pace and to accept the bit. Schooling over jumps does not change the horse's ability, but does build up its confidence in itself and in its rider. The showjumping circuit has developed into a highly professional and commercial world. There are two seasons that occupy the whole year. The summer season lasts from May to October, culminating in the Horse of the Year Show, and consists mainly of outdoor shows. The winter season extends from October to April, and competitions are usually indoors. The temptation is for riders to overwork their horses, but showjumping horses need a spell off work as much as any other competing horse. The performance of the horse and the number of seasons of tough competition that a horse will be able to withstand depend on a correct combination of schooling, fitness, work and rest. Properly treated, a showjumper can compete at the top level well into its late teens. A horse will also last longer if it is not competed too early, before it is ready both physically and mentally. Plenty of time must be allowed to get the horse fit. If a horse is fittened too quickly, it can be detrimental to the time that it can stay fit, and this can affect not just one season but all the horse's competitive life. As with all disciplines, true fitness is based on a firm foundation of long, slow work. Different trainers have different ideas on how long a horse should stay in work: (1) Six weeks' semi-rest, 6 weeks' fittening work and 3 months' competition twice a year. (2) Three months' rest, 8 weeks' fittening work and 6 months' competition. A long season like this would be broken by two short semi-rest periods of up to 2 weeks. The number, timing and duration of these short breaks would depend on the individual horse. The less rest the horse is given, the quicker it can come back to competition fitness. However, the first 2 weeks of any fittening programme should consist of walking work on the road. The next 2 weeks should involve walking, trotting and basic ground work. Canter work, more intensive schooling and jumping exercises would be introduced no earlier than 4 weeks after the horse has been brought up from its

< previous page

page_234

next page >

< previous page

page_235

next page > Page 235

rest. The horse must be walked for 15 to 20 minutes before a schooling session to give it adequate time to warm up. An older, experienced horse will need less schooling than a young horse, and the seasoned campaigner would probably do very little jumping at home. The young horse, however would need more schooling so that it arrives at the competition supple and obedient, and this may involve jumping two or three times a week. Gymnastic jumping is useful for building both confidence and the correct muscles. Like the dressage horse, it is possible to get the showjumper to a suitable degree of fitness by schooling in an arena, because the movements practised at home are the same as those performed in competition unlike the racehorse or eventer, where a great deal more is asked in competition. This, however, would not be ideal; a horse can easily get bored and stale and start to develop evasions, so work must be varied, including quiet hacks, canters on suitable ground and perhaps even a day's hunting. From a scientific viewpoint, the type of training outlined here is ideal, provided the horse meets in training a threshold of stress similar to that which it is going to meet in competition. Canter work must not be neglected, because stamina is important in an animal that may spend several long days each week away from home and may jump five or six rounds a day, including timed jump-offs which place great stress by requiring fast turns and changes of pace. The horse that is a speed specialist should be trained by giving faster work to develop its aerobic capacity, while the puissance horse should be trained for power in a similar way to the dressage horse. Training the Racehorse The Point-to-Pointer The initial training of the point-to-pointer will be the same as for the hunter. The horse may be got fit for the opening meet of the season if being raced early in the point-to-point season, or may be got up slightly later if racing late in the season. The point-to-pointer has to qualify by hunting six to eight times during the hunting season with one recognised Hunt. Bearing in mind the treacherous conditions that can prevail after Christmas, it is wise to qualify the horse before the end of December. This way, the horse can do 1 day a week during the first 2 months of the season leaving a clear 6 weeks or more to prepare it for its first race. Specific training for the forthcoming point-to-point season should

< previous page

page_235

next page >

< previous page

page_236

next page > Page 236

begin about 4 weeks before the horse's first race, provided the horse is hunting fit, in good condition and wellmuscled. Hunting fit is not racing fit even a horse capable of hunting 2 days a week is not trained adequately for galloping for 5 km (3 miles) over 1.5 metre (4 ft 6 in) fences. The hunter rarely gallops steadily for long distances; there are checks, changes of pace and a variety of obstacles. The hunter may have a great capacity for endurance, but its capacity for fast work needs to be developed. In other words, the point-to-point horse has to be galloped during training, and a suitable place must be found. This is not to say that if the horse is racing over 5 km (3 miles) it must be galloped for 5 km during training this will tire the horse rather than get it fit. It is generally accepted that horses should do fast work no more than twice a week, but the duration and speed of the fast work varies according to different trainers. Two different training programmes are given here and show alternative ways of reaching the same goal. Programme 1 The aim of the first programme is to keep the hard, muscled-up hunter fit by giving a long, slow workout four times and developing its gallop by fast work twice a week. Monday: Walking, trotting and possibly a quiet canter (300 to 350 m/min) for about 1.5 km (1 mile); 60 to 90 minutes in total. Tuesday: Walk, trotting and a steady canter (350 m/min) for up to 3 km (2 miles), according to the type of horse. Wednesday: Steady canter (350 m/min) for 1.5 km (1 mile) 20 to 30 minutes' walk and trot and then a 1 km (5 furlong) gallop (600 m/min). Thursday: An easy day; walk and trot for 60 to 90 minutes. Friday: As Tuesday. Saturday: As Wednesday. Sunday: Rest day. This programme is very traditional, using prolonged periods of slow canter work to build up the horse's capacity for endurance, and keeping fast work to the minimum to avoid wearing the horse out. Programme 2. In the second programme, the horse is again galloped twice a week. Initially, the horse is asked to go at a fast, hunting canter (about

< previous page

page_236

next page >

< previous page

page_237

next page > Page 237

400 m/min) for about 2.5 km (1.5 miles). This is gradually increased over the next month to 3 km (2 miles) at a medium gallop (about 500 m/min). One day a week the horse is given a sprint up a hill. Moving fast uphill puts less strain on the horse's legs than galloping on the flat, but it does demand a lot of the heart and lungs. Horses should not be asked to gallop downhill during training, as this puts a lot of strain on the front legs and increases the risk of tendon breakdown. As the horse gets fitter, a sprint is included in the gallop; the horse is asked to stretch out over the last kilometre of its 3 km (2 mile) gallop. The horse should not be pushed to its limits, and the rider should always feel that the horse has something in reserve. The rest of the week, the horse's exercise would consist of 60 to 90 minutes' hacking on roads and tracks, including as much uphill trotting as possible. Thus the weekly programme would look something like this: Monday: Walk and trot, 90 minutes. Tuesday: Steady, progressive warm-up 3 km (2 miles) gallop at 500 m/min followed by a steady cool-off and winddown. Wednesday: As Monday. Thursday: As Tuesday. Friday: As Monday. Saturday: Uphill sprint. Sunday: Rest day. The two programmes given above are typical of those used in practice. However, previous chapters may have suggested that traditional methods will soon have to incorporate modern ideas in order to stay successful. Jump-Schooling The training programme of a point-to-point horse will also include some jump-schooling. If the horse has raced before, it will not be necessary to give him much jumping practice a gallop over schooling fences a week or so before his first race should serve as an adequate reminder. If the horse has not raced before, it should be introduced to point-to-point fences gradually. Asking a hunter to gallop over fences is asking it to do exactly the opposite of what it has been doing in the hunting field. The hunter is taught to take its fence at a steady pace and to jump big and clear. The point-to-pointer must throw caution to

< previous page

page_237

next page >

< previous page

page_238

next page > Page 238

the winds, jumping out of a fast gallop, not 'dwelling' at the fences, and galloping on immediately upon landing. In order to establish this confidence, it is best to start with small, solid hurdles, well sloped and no more than 1 metre (3 feet) high. These fences are easy, and very soon the horse will become familiar with them and will gallop on over them, judging the take-off distance with confidence. The horse can then progress to brush schooling fences. Again these should not be too big and forbidding the horse must not be intimidated at this stage. Jumping with a more experienced horse can be helpful. The older horse can act as a lead initially and then jump alongside the novice. It is important that the young horse is not flustered by jumping in a crowd, although this may happen in a race. Races are usually won by horses that jump smoothly and quickly. This can only be accomplished by a horse with confidence in its own jumping ability, brought about by sensible schooling. National Hunt Racing The hurdler and 'chaser may come up through the ranks of flat-racing horses or may be bred specifically for jumping. A horse that has raced on the flat will be easier to get fit than an untouched youngster. However, a great depth of fitness is needed for National Hunt races, particularly for the longer distance races. This means that some trainers put a greater emphasis on initial slow work, allowing up to 8 weeks' walking and trotting before canter work starts. The early routine is similar to that used for getting hunters fit and is the same in most yards, consisting of about 90 minutes of walk and trot work, including hill work. There is great variation between yards in the cantering and galloping routine. After the initial slow work, canter would be introduced on, perhaps, 2 days a week, each canter session being about 2.5 km (1.5 miles). This would be gradually increased to 4 work days a week, so that the weekly programme would be as follows: Monday: 90 minutes of road work, walk and trot. Tuesday: 2.5 km (1.5 miles) cantering (half speed). Wednesday: Fast work. Thursday: 30 minutes' walking only. Friday: Cantering (half speed). Saturday: Fast work. Sunday: Rest day.

< previous page

page_238

next page >

< previous page

page_239

next page > Page 239

As with any horses kept at peak fitness for prolonged periods, mental happiness is essential for success. To prevent the horse from getting bored or stale, exercising routes should be varied; the horse could be turned out for short periods in a paddock and other forms of work, such as swimming, could be used. Facilities for galloping jumpers are important, but need not be as straight as for the relatively immature flat-race horse. It is not necessary to gallop horses over the distance that they race over. If the horse is in good health and well prepared from its road work, it just needs to be topped up once a week by strong work and kept supple on two other days by half-speed canters over 2.5 km (1.5 miles). The skill of a good trainer lies not so much in getting the horse fit but in keeping it fit for a series of races. Once a horse is fit, it should be kept simmering and only brought to the boil on race days. This means that the jumping horse is rarely given a full-speed gallop during training; the horses are worked well up into the bridle (never on a loose rein) at a half-speed gallop, so that they are able to quicken readily if asked for the last 500 metres (23 furlongs). The horse's jumping ability has such a large influence on the outcome of the race that home trials of a horse's fitness are rare. Schooling over fences is obviously very important, and before being taught to jump the horse must be obedient to the aids and have done enough groundwork to be balanced and co-ordinated. The young horse should be taught to jump out of a trot or slow canter over small fences before being asked to jump schooling hurdles. Training the horse to jump loose in an indoor or outdoor arena is useful and gives the young horse confidence in its ability to jump, teaching it to make its own adjustments without the weight of the rider on its back. Just as interval training and other modern methods can be used successfully to prepare event horses, so too can these methods be used to prepare 'chasers. In particular, blood profiles and optimum racing weights are commonly accepted. Heart-rate monitors are still regarded as being in the 'secret weapon' category, but they probably offer the greatest scope for improved performance, monitoring fitness, detecting subclinical disease, and thus offering trainers improved results and improved economics. Training the Flat-Race Horse Flat racing is the most natural of all the equestrian sports. Horses are athletes designed to use their speed to escape predators. The racehorse has to be taught to accept the rider's weight and a certain amount of

< previous page

page_239

next page >

< previous page

page_240

next page > Page 240

control, but the crucial factor determining success is the horse's fitness. The horse must be got correctly fit for certain races which are carefully selected. Races vary in distance from 5 to 20 furlongs (about 1 to 4 km) and, like human runners, each horse has its own best distance. Horses tend to stay better as they get older; 2-year-olds are not raced over distances greater than 8 furlongs. Training flat horses is complicated by the fact that as 2-, 3- and even 4-year-olds, these horses are still growing and maturing. The body systems of young horses are frequently unable to withstand the stress of training, leading to a high percentage of wastage in racing Thoroughbreds. The majority of horses bred to race on the flat are broken in after the yearling sales in October, and so start work at 18 months old. The breaking programme will involve lunging and long-reining, perhaps even long-reining through starting stalls. This gets the young horse used to stalls early on, avoiding problems at a later date. After about 4 weeks of groundwork, the horse will be backed and ridden away at walk and trot for 3 to 4 weeks. The youngster will be introduced to canter work on the gallops from about New Year onwards, beginning over 500 metres (2.5 furlongs) and gradually working up to 800 metres (4 furlongs). As the horse learns to canter in a balanced way and becomes fitter, a second canter is introduced into the same training session. The next step is for the 2-year-olds to canter 'upsides', i.e. alongside each other. Canter work should be preceded by 20 minutes' walking and some trotting; as the canter work increases, the length of time spent trotting is reduced so that the horse is having about 75 minutes' exercise. As the horse gets fitter, its 'swinging' canter can progress to a half-speed gallop and eventually a sharp gallop twice a week. Initially, the fast work should be over very short distances; these are gradually increased, depending on the race the horse is being prepared for. Just before the race, the fast work should be shortened and quickened to prepare the young horse for full racing speed. Flat horses are galloping specialists, and their training regime is geared to ensure that muscle development is confined to those muscles used for galloping any extras are considered unnecessary. This means that their work is mostly composed of galloping and cantering, interspersed with hill work, swimming and walking on a horse walker. The longer a young horse is given to mature and muscle-up, the better. Many horses will not race as 2-year-olds, and only make their track debut as 3-year-olds; others mature earlier and are capable of racing as 2-year-olds. Developing muscle is accomplished by steady

< previous page

page_240

next page >

< previous page

page_241

next page > Page 241

exercise gradually increasing in duration, walking, trotting and hill work. The youngster should not be cantered until it can trot steadily and in a straight line, using its hocks and shoulders. The jockey must be careful to ride on both diagonals at the trot so that muscle development over the back is equal and balanced. Initially, the young horse should be cantered slowly so that it can find its own balance before being asked to gallop. Scientific knowledge suggests that racing involves maximum contraction of the muscles involved with galloping; thus a more strenuous component must be brought into the training programme. For the body to have a more efficient way of disposing of the high lactic acid concentrations built up during a race, it is important that these levels are experienced during training. A racehorse can be trained using a speed endurance schedule, which is similar to interval training but is based on repeating high intensity exercise over short distances. Exercise might consist of several maximum gallops over 400 metres, with intervals of trot between for the horse to recover partially. This type of training is rarely seen in racing yards and it is not known if a young horse could stand this sort of regime either physically or mentally; however, for the older flat-race horse it holds promise of improved performance. It is interesting to note that, using such methods, human runners have improved their performance out of all recognition. Accepting that training the horse is a totally different science, it is still interesting to note that racing trainers tend to use the same methods as their grandfathers and to produce only the same speeds. It may be that the legs of the horse are the limiting factor, but it is possible that a trainer using new techniques and equipment will start to break equine speed records. Fittening the cardiovascular and respiratory system of racehorses is vital, but often the hardening-up of young bones and joints is neglected. It takes at least 6 months for bones to strengthen; hence the high incidence of lameness problems in young flat horses. Training the Driving Horse There are many variations in the sport of driving, from scurry to marathon, concours d'elegance to Hackneys. This means that the type of horse used and the degree of fitness required will vary enormously. The basic training, after the horse has been brought up from a rest, does not vary greatly. There is an initial period of walking work, either under saddle or in long-reins, lasting about 35 to 45 minutes per day.

< previous page

page_241

next page >

< previous page

page_242

next page > Page 242

The horse must be made to use itself in walk, alternately collecting and extending the walk. Lunging and work in harness can then be introduced, including some trotting work. Lunging can be gradually increased up to 45 minutes per day. It is from here that the training programme will diverge, depending on the competitive goals and sub-goals. A 'single' horse being driven at an exhibition class could start the fittening programme in March, working up to 30 minutes on the lunge, and be ready for showing in May. The marathon team horses that are expected to pull a load of about a tonne for 13 to 20km (8 to 12 miles) would need up to 45 minutes on the lunge to reach adequate fitness. A horse would need 3 months' training to be fit to compete in a three-stage driving trial. A form of interval training can be used, as these horses need to be very fit; 3 minute trot intervals followed by 3 minute walking intervals can be used, the number depending on the horse's reaction to the work. Once the horses are trotting five 3 minute intervals with ease, the working time can be gradually increased. The rest interval should remain at 3 minutes, and exercise repeated until the horses are sufficiently stressed but not overstressed. The next stage in the ridden horse would be to introduce canter work, but fast work is obviously unsuitable for the driven horse and hill work should be included to increase fitness. It is useful to have a measured drive; the driver should know the ideal time for the drive at certain points along the route, and he should carry a watch. Gradually, as the horses get fitter, aim for this optimum time. This measured interval drive should be used on a 4-day schedule. By the time the major competition goal arrives, the team should be able to go 1.5 times the distance of the cross-country phase without distress. As the horse gets fitter, it may be necessary to adjust its tack to allow for muscle development. The horses must work together as a team, and the driver must know his horses and recognise subtle signs of distress or abnormal behaviour. During the cross-country phase, it is possible for horses to become tired and even exhausted. They may still have the ability to go on but they lack the muscle control and mental ability to cope with a problem for example, a hazard on the cross-country. Fatigue is probably the biggest obstacle of all. The horse's gait changes and the incidence of accidents and injuries increases. Fatigue must therefore be avoided by using a thorough training programme. It must always be remembered that the driving horse has the added burden of having to move within a gait; it cannot use its own natural rhythm.

< previous page

page_242

next page >

< previous page

page_243

next page > Page 243

The progression through the natural paces of the horse provides the greatest efficiency of energy utilisation, as measured by oxygen consumption. Each horse has its own speed within a pace at which it uses energy most efficiently. Horses working in harness actually have a greater energy demand because they are unable to move freely, so when selecting driving horses it is essential to choose those which inherently have the power, pace and stamina for the work. For a pair or team, it is of vital importance that they are complementary in terms of temperament and that their gaits are fully compatible. Training the Polo Pony The game of polo was first described in a Persian manuscript dated 600 B.C., which means that the game has been played for over 2500 years. It is a very demanding sport, taxing ponies both physically and mentally. While each chukka only lasts 7 minutes, the pony is on the go all of that 7 minutes, with sudden changes of pace and direction. After basic fitness has been achieved, schooling plays a very important part in the training programme; the pony is taught to be agile and able to adjust its feet quickly and nimbly during only slight changes of direction. To accomplish this, the pony is taught to be slightly behind the bit and off its forehand. Basic Training It is generally accepted that it takes 2 years to 'make' a polo pony. Ponies are usually taught the basics when they are 4 years old; as 5-year-olds they play minor competitions and are ready for a full season of matches when they are 6 years old. The basic training of a polo pony is no different from that of any other riding horse. The pony is taught to move freely forwards in walk and to trot in a balanced manner, to move away from the leg and canter on the correct lead. Specialist Training There are three main movements that need to be taught to the pony. These are: to change legs and alter balance immediately when asked to stop and start abruptly from any pace to turn on the haunches.

< previous page

page_243

next page >

< previous page

page_244

next page > Page 244

The polo pony's ability to change legs at the canter at the slightest indication is vital if it is to be balanced at all times. The fast changes in pace and direction needed in the game of polo demand that the horse is always balanced. A young, green pony will find sudden changes of pace very difficult and tiring. If these movements are introduced before the pony is fit, there is a risk of strains and sprains. Thus teaching a pony to stop abruptly from any pace begins by teaching it to stop instantly and correctly from walk. Once the pony understands the aids and gets fitter, faster paces can be introduced. The turn on the haunches is again difficult for the youngster, and puts considerable strain on the hocks. If the movement is introduced at walk, the benefits are twofold; the pony learns the aids without being hurried and confused, and the hocks become gradually strengthened. Once the pony has mastered these movements, it can be introduced to stick and ball. It is not advisable to hit a ball off a pony until its training is well underway and it is under full control. Time and patience are needed at this stage if the pony is not to be frightened. It is also wise not to over-corn the pony so that it is not too fresh. There are several other things that may frighten a pony when it is starting to play polo. These include meeting other ponies coming towards it at speed, meeting swinging sticks, meeting the ball and being 'ridden-off' by another pony. These circumstances should all be encountered in training so that the pony gains confidence. Fitness Programme The polo season begins at the end of April and ends in September. Generally, a pony would play one or two 7 minute chukkas plus one practice session per week. (Low-goal matches consist of four chukkas, high-goal games of six.) A fit polo pony must thus be capable of galloping, twisting and turning for 14 minutes, two or three times a week. If this degree of work is to be maintained for the entire season of 4 months, the pony needs to be very well prepared and fit. Two months is the minimum time in which it is possible to prepare a pony for match playing. If the pony is to stay fit throughout the season, it is wise not to overplay it for the first month of matches, ideally restricting it to one chukka per match. It is important to try to maintain optimum performance for as long as possible without overstressing the pony. Too much stress increases the incidence of

< previous page

page_244

next page >

< previous page

page_245

next page > Page 245

injury and may also sour the pony. If the pony is to respond willingly to the demands of the game, it should not be placed in any situation with which it is not capable of coping. Polo ponies are brought up at the end of February or the beginning of March. There is an initial period of walking work lasting 1 to 2 weeks. Throughout the training programme, one pony will be ridden with two being led from it. The ponies are ridden in rotation so that their skin becomes hardened and they are used to carrying the rider's weight. Trotting is usually introduced early on in the training programme and gradually built up, so that by the end of week 4 ponies are being worked for 90 minutes, 30 minutes of which would be trotting. This basic programme serves to get the horses muscled up, develops stamina and 'hardens' the legs. The polo pony also needs to develop its gymnastic and athletic ability, and schooling exercises should be introduced towards the end of the first month. These exercises would involve the movements previously described and some stick-and-ball work. Canter work begins 3 to 4 weeks before the first match is scheduled. Canter work is considered very important, with ponies being given up to 20 minutes' canter-work a day plus road work. Occasional fast work may be given prior to and during the season. This would consist of a short, half speed gallop to act as a 'pipe-opener' and to check that the pony is correct in its wind. Too much galloping is not recommended, as it tends to make ponies overexcited and gets them on their forehand. Polo ponies are worked hard for short periods of time during a match, and the game demands explosive bursts of acceleration and great muscle power. Once basic fitness has been obtained through 4 to 6 weeks of slow work, training must concentrate on building up muscle power. These powerful, accelerating muscles are composed of a majority of fast twitch low-oxidative fibres which rely on anaerobic respiration. The fibres must be encouraged by performing in training the movements executed in the match, which means that schooling sessions are essential, not only in terms of obedience but also for fittening. In scientific terms, polo ponies would be more efficiently trained by giving short intervals of maximal work, i.e. sprinting. This would bring about maximal development of the anaerobic system when combined with schooling exercises. However, the constraints of the labour force available mean that ponies are usually exercised in threes at a steady canter. Resting polo ponies are often turned away on meagre rations over

< previous page

page_245

next page >

< previous page

page_246

next page > Page 246

winter and so lose condition. These horses should be fed at least a good maintenance ration until they come back into work. This will make the training process easier as polo ponies should be in good condition when brought in.

< previous page

page_246

next page >

< previous page

page_247

next page > Page 247

18 The Speedtest and Fartlek System. The success of training depends on the ability of the trainer to assess the horse's potential and to proceed accordingly, improving the horse's strong points and reducing its weak points. Breeding, conformation and 'feel' of a horse must all be taken into consideration. Dr Donald McMiken, working in America, has adapted some training methods used by human athletes for conditioning racehorses. The Speedtest System This system involves a three-stage programme. The horse is given a test at the end of each stage, hence the name 'speedtest system'. The idea is to think of conditioning, or getting a horse fit, as a pyramid, starting at the base with slow work and, as the muscles and skeleton adapt, gradually increasing to fast work and competition at the peak. The broader the base established, the higher the peak that can be reached. The First 3 Months A mature horse would spend the first 3 months of the training programme doing a lot of slow work at walk, trot and canter. After 2 weeks' walking only, slow trotting would be incorporated so that the horse would be doing 3 km (2 miles) of mostly trotting. This would be built up so that every third day the horse would be doing 10 km (6 miles) of mostly slow canter work. The work on the other two days would be easier and shorter. The horse should be exercised five or six times a week. This part of the programme would have to be stretched if the horse were immature or had never been got fit before. Once an older horse has been fit and then let down, it is much easier to get it fit again. The aim of this slow work is to strengthen the bones, muscles, tendons and ligaments. Different tissues grow stronger at different

< previous page

page_247

next page >

< previous page

page_248

next page > Page 248

rates: bones and tendons adapt to work more slowly than muscle; hence the long period of slow work. It is important not to relentlessly pile more and more work on the horse. To this end, the programme is worked in 4 week cycles: a moderate week, a hard week, a moderate week and an easy week. This means that the horse's body has a chance to repair any damage that may be done during the hard week before it is asked to work again. In traditional training routines, the horse may appear to be getting stronger but the damage can be slowly building up. Fartlek Fartlek is a Swedish word that translates as 'speed play'. This is a term used by human athletes to describe a philosophy as a training method. Human runners run as the ground allows and as their bodies tell them, slowing down and speeding up as they feel appropriate. Thus the man is always running within his limits, alternating fast and slow work in an essentially unplanned manner. Fartlek is used to describe gallops the horse is given towards the end of the 3 month period. These are short gallops, 200 to 600 metres (200 to 600 yards). Obviously, translating fartlek to horse work is difficult the horse cannot tell you how it feels. This is where the use of a heart rate monitor comes in. Electrodes in the girth collect the heart rate information and transmit it to the wrist monitor, giving a continuous readout so that the rider knows how stressed the horse is all the time. Heart rate monitors measure muscular effort and energy production. Racehorses are given gallops of less than 1 minute and their heart rate is pushed up to 200 to 210 beats per minute. An eventer would probably only need to go to 190 to 200 beats per minute. For gallops of longer than 1 minute (as occur later in the programme), the heart rate should not be allowed to go any higher than 180. If the heart rate goes too high, the horse is slowed slightly so that it is never being overstressed. Horses are never galloped more than twice a week, and not at all during easy weeks. Speedtests Speedtests are used to determine whether or not the horse is ready to move on to the second phase of the programme. This is a moderate gallop of 4 km (2.5 miles), during which the heart rate is recorded. The

< previous page

page_248

next page >

< previous page

page_249

next page > Page 249

heart rate and speed are compared with the horse's previous efforts and with those of other horses in training. There is no set point at which a horse is said to be ready to move on, but a progression in heart rate indicates increasing fitness. The Next 6 Weeks The second phase lasts about 6 weeks and is designed to strengthen the respiratory system and the muscles. The only way to do this is by stressing these systems, so the amount of fast work increases. Racehorses are asked to gallop a mile or so at about 2 minutes to the mile (1 to 2 km at 800 m/min). Hill work once a week is a good idea, as it sends the heart rate up at slower speeds and there is thus less wear and tear on the front legs. The eventer would be asked to do a 3 to 5 km (2 to 3 mile) gallop, the speed being adjusted so that the heart rate never goes above 180. The earlier fartlek sessions have acted as groundwork for this stage. Fast work takes place twice a week, the other days being similar to the first stage, but speed is increased and distance reduced. At the end of about 6 weeks, the horse undergoes another speedtest to show whether or not it is fit to continue to the next stage. The Third Phase During the third stage the conditions of the competition are simulated, the duration of work is reduced and the speed is increased. For the racehorse, this means work at speed. This fast work is performed in intervals: the horse gallops, say, just under a kilometre (about half a mile) at racing speed, trots until the heart and respiration rates have recovered, and is then galloped again. The aim is to push the horse to near maximum to get the greatest fittening effects and yet to avoid fatigue (see Chapter 16). Three intervals at fast speeds twice a week are adequate. The distance of the gallops may be increased, but the number of workouts is not changed. A final speedtest is given before the horse is raced. The eventer would use speeds, distance and activities appropriate to its competition. For example, an Advanced event horse would do three gallops of 1 km (0.75 miles) at steeplechase speed. A Novice event horse need gallop no faster than the speed needed in competition. It is claimed that this method of training produces a much higher level of fitness than conventional methods, and this appears to be

< previous page

page_249

next page >

< previous page

page_250

next page > Page 250

borne out by scientific studies. In Sweden, adult horses trained for only 5 weeks in this way developed greater muscle endurance (measured biochemically) than horses actually racing. Horses involved in dressage and showjumping will not need the third stage of the programme, and some will not need the second as their early work will have strengthened them enough. Schooling for dressage and jumping can be fitted into the work of the first phase. Light workdays and easy weeks are good times to practise early dressage movements because these exercises are not too demanding physically. Jumping and advanced dressage are more stressful and fit into the moderate week's work. Thus not only are conditioning and training combined, but the work pattern is varied and keeps the horse from being bored.

< previous page

page_250

next page >

< previous page

page_251

next page > Page 251

19 Monitoring Fitness One of the biggest problems the trainer or rider faces during a horse's training programme is judging how much the horse can take. Every time the workload is increased, the trainer has to decide whether the horse can stand the work or is on the verge of injury or overstress. Although the horse's legs may be carefully examined for heat and swelling, by the time these external signs become apparent the damage may already be serious enough to interrupt the training programme. In an effort to combat the 'trial and error' of getting horses fit, there are more and more trainers (particularly in the U.S.A.) using technical equipment to assess their horses' fitness. Thermography This technique uses an infra-red camera to record changes in temperature. It can be used to spot wear and tear in the legs and feet where the inflammatory reaction has begun and the temperature of the area has increased but has not yet led to swelling and lameness. This equipment is very expensive and is only used in a few specialised equine centres. It is possible to buy a handheld sophisticated thermometer that, when skimmed along the leg about a centimetre above the surface, gives a digital readout accurate to 0.1 of a degree. The best results appear to be obtained using 'provocative cooling'. The legs are splashed with alcohol to cool them, and the thermometer measures which spot heats up the fastest. Ultrasound. Ultrasound imaging uses ultrasound waves to produce detailed views of body tissue and is successfully used to detect pregnancy. Ultrasound bone analysis records the speed at which ultrasound waves pass through bone. There is a correlation between ultrasound reading and density of bone. As has been previously described, bone becomes more

< previous page

page_251

next page >

< previous page

page_252

next page > Page 252

dense and strong with work, and ultrasound readings will reflect these changes in bone strength and also indicate the presence of damage. Bone under stress may suffer tiny microfractures that begin to build up and may lead to a serious fracture. The equipment is expensive and the results are difficult to interpret. However, as expertise grows, ultrasound bone analysis may help to spot bone damage early and monitor the horse's progress in one aspect of training. It may prove particularly useful for 2-year-old racehorses. Gait Analysis This technique involves filming horses at different paces and analysing their action frame by frame with the aid of a computer. The horse's gait is rated for efficiency and studied for oddities that might predispose to future unsoundness. The racehorse's gallop might also be compared step by step with the gallop of past champions. Force Plates The Swiss-designed Kägi gait analysis system is designed to provide the vet and the trainer with another pair of eyes. The horse is walked or trotted across a 40 metre × 1.20 metre track made of hard-wearing rubber, with a central plastic section which carries 160 sensors and can be used in any weather. The sensors can record 1790 details in 0.5 seconds, and the computer printouts are available in 10 minutes. Through the computer, the printout will record all the forces acting on each leg, both independently and jointly with the other legs. Professor Mueller of Zurich University has developed printout patterns of sound horses and horses with various forms of lameness, and comparison to these can help the vet diagnose lameness and the trainer assess soundness. However, interpretation of the results is not easy and correct interpretation is, of course, the first essential requirement for using the system sensibly. Lactic Acid Monitoring A major goal of training is to increase the horse's tolerance to the lactic acid build-up incurred during fast anaerobic work. Lactic acid is now thought to have a role to play in predicting a horse's performance ability. In a group of untrained horses, individuals of greater natural ability will travel faster before they first produce lactic acid. As a horse gets fitter, it is able to go faster before lactic acid production starts.

< previous page

page_252

next page >

< previous page

page_253

next page > Page 253

This suggests that (a) it may be possible to screen youngsters for lactic acid tolerance early in their training programme, and (b) lactic acid monitoring may be able to follow the effects of training and indicate a fall in exercise capacity due to injury or overtraining. Lactic acid production is dependent on fast twitch low-oxidative muscle fibres. Lactic acid production increases as the horse's system reaches its oxygen-delivery capacity, and the level at which this build-up begins depends on the horse's fitness. This threshold of lactic acid build-up (acidosis) is called the 'anaerobic threshold' and indicates the horse's level of fitness. As the horse gets fitter, the anaerobic threshold is delayed. If the threshold stops rising, the horse has reached its limits in terms of lactic acid tolerance and fast twitch muscle fibre use in other words, it has reached the limit of its ability to gallop fast. If the threshold starts to fall, this indicates overtraining, illness or injury. A step test can be conducted consisting of a series of workouts at slow, medium and medium-fast speeds. The horse is given jogging relief between tests to get the heart rate down to about 100 before it is asked to work again. This step test can be given under fairly consistent conditions and the horse's performance, in terms of lactic acid build-up, monitored throughout training. Blood samples are taken before training starts and after each of the three speeds in the workout. The blood is then analysed for the lactic acid content, using a sophisticated machine. Taking the blood sample at the same time after each of the three steps is vital, as the lactic acid level can drop quickly after exercise stops. A graph of the lactic acid values and speed of exercise can be plotted which will demonstrate where the anaerobic threshold lies. Training a horse just above the lactic acid threshold helps achieve rapid progress in the horse's ability to perform fast work over a distance, and also appears to reduce the incidence of training and racing injuries. Muscle Biopsy This technique has been mentioned earlier. A small piece of muscle tissue is removed from the horse's rump (gluteus medius muscle) with a biopsy needle, and is immediately frozen. The tissue is still 'alive', and is taken to the laboratory where it is thawed, stained and evaluated under the microscope. All horses have a mixture of various fibre types, and the biopsy is designed to show what proportion the fibres are in, how big the fibres of each type are, what their aerobic potential is and how much fuel is stored in them.

< previous page

page_253

next page >

< previous page

page_254

next page > Page 254

A horse which has a high percentage of slow twitch fibres (Type I) can excel in endurance work but will always be at a disadvantage when bursts of speed are needed. A horse with a high proportion of fast twitch low-oxidative (Type IIB) is a natural sprinter. Fast twitch high-oxidative (Type IIA) are the most versatile, able to increase both power and endurance. Thus a knowledge of a horse's muscle fibre type can help assess its potential for various sports. Heart Rate Monitors These have also been discussed previously. Monitoring a horse's heart rate is becoming increasingly popular as a way of assessing fitness and monitoring the success of a training programme. Videos Recording a horse's performance on videotape can be very useful in monitoring its progress. The horse's movement and action can be watched in slow motion; the tape can be stopped so that every stride and movement can be analysed. If a horse is not jumping properly or a dressage horse is not performing movements correctly, the training programme can be adjusted to include the necessary specific exercises. Computers These machines can help keep track of all the variables that may affect a horse's training programme for example, the horse's health, the condition of the going, the weather, etc. A computer program can be used which reminds the trainer of factors that will determine how much work the horse should receive: soundness, history, most recent work and reaction to it, level of competition, and so on. With the appropriate information fed into it, the computer can come up with a description of what work should be next in the training programme. A computer may not be vital to success, but it can act as a valuable tool, preventing the trainer from overlooking factors that may affect soundness and performance.

< previous page

page_254

next page >

< previous page

page_255

next page > Page 255

20 Equine Sports Physiology Any experienced competitor will tell you that competitions are won at home; in other words feeding, fitness and stable management are as important as schooling and competing in producing a horse that is capable of winning. There is no excuse for competing a horse in any discipline if it is not fit enough; riders need to be aware of the demands that competition will place upon their horse and train it accordingly. Horses are expensive to keep, and if we lose valuable time through injury which could have been avoided by having greater understanding, we have only ourselves to blame. The horse depends on us to provide it with the very highest standards of care and attention; only then will it reward us with its best. No matter how fit the horse and how careful the management, however, accidents will and do happen. If the horse is to make a speedy and full recovery it is essential that the injury is correctly handled from the start. For many years horses that sustained soft tissue problems, such as tendon injuries, were treated with box rest followed by a long spell of rest in the field; advances made in human sports physiology and sports therapy, however, have shown us that this is not the best way to ensure full recovery and use of the affected part. The chartered physiotherapist and the equine sports therapist are now important members of the team which manages the equine athlete, helps it reach its performance potential and also aids effective recovery from injury. No football team would travel without its 'physio' and we demand much more athletic feats from our show-jumpers and event horses! A chartered physiotherapist specialising in animal therapy has to undergo a 3-year training course at a recognised college. Graduation leads to membership of the Chartered Society of Physiotherapists, a body recognised by the medical profession and bound by a code of practice. In the 1980s the Chartered Society of Physiotherapists and the Royal College of Veterinary Surgeons formed a special interest group the Association of Chartered Physiotherapists in Animal

< previous page

page_255

next page >

< previous page

page_256

next page > Page 256

Therapy (ACPAT). Membership of this association requires full qualification of the Chartered Society of Physiotherapists, 2 years' post-registration work in the human field and seeing practice with two veterinary surgeons, who assess and confirm the physiotherapist's ability to work with and handle animals. The constitution of the association binds members of ACPAT to work under veterinary supervision, treating cases after diagnosis. A recent development in the educational programme is that a part-time course leading to a postgraduate qualification in chartered animal physiotherapy is now necessary. Equine sports therapists may have travelled along different qualification routes they may be chiropractors and manipulative therapists with a specialist interest in performance horses. During recent years scientific advances have led to many changes in the management of injuries; immobility is generally not advocated, and better healing results from the use of passive movement through selective techniques and physiotherapy. This is both more desirable and physiological correct. Physiotherapy is holistic in its approach, using assessment techniques to determine whether the horse is able to perform to the best of its ability and identifying any biomechanical, musculoskeletal or external influences (such as tack or the rider) which may be causing a decrease in performance ability. Physiotherapy, if correctly used, should provide a complete regime for the horse, ranging from preventive care and the instigation of a treatment regime to rehabilitation techniques which will maximise performance. A therapist's skills include the correct application of electrotherapy, the use of manual techniques and the development and implementation of exercise programmes. The type and extent of the injury and how long the horse is incapacitated will all affect how completely the horse recovers. In order to be fit enough to compete at its best, the horse has to be able to use its body to maximum affect; the horse may appear sound and fit, but if healing has not been complete the horse is vulnerable to further injury and possibly irreversible damage. Injuries can be broadly divided into two categories: (1) traumatic injuries (2) overuse injuries. Traumatic Injuries. Traumatic injuries are usually sudden. You know something has gone wrong as the horse feels the immediate effects of the injury perhaps pain, swelling, bruising or an open wound. A traumatic injury can be

< previous page

page_256

next page >

< previous page

page_257

next page > Page 257

extrinsic, due to an external cause such as a direct blow, a sudden twist initiated by a change of direction or even a fall. Alternatively it can be intrinsic for instance, a muscle may rupture in mid-performance without obvious cause. Traumatic injuries are relatively easy for the specialist to diagnose; difficulties only arise if the injury is particularly severe, or if complications occur straight after the injury which are not immediately apparent. Prevention is better than cure, and one way to avoid traumatic injuries is to minimise risk factors; choose the terrain you work over carefully and assess the state of the going before demanding too much of your horse. Equipment should be checked regularly and protective boots used where necessary; boots should be appropriate for the job and well fitted. Overuse Injuries Overuse injuries are more subtle and are seen as gradually increasing pain which is associated with a particular activity, usually repetitive in nature. In order to avoid this type of injury the horse's body must be given time to adapt to repetitive stress. If you make a sudden alteration in the horse's training programme its body may show signs of overwork. Increasing the horse's workload has to be a gradual process, building up in easy stages. The horse will give you warning signs such as illness, fatigue, abnormal heat or swelling, pain and stiffness: take notice of them, they are indications that the horse should stop what it is doing and be assessed for an accurate diagnosis of the problem. You then have to start the process of recovery with physiotherapy which will incorporate pain relieving and other treatments designed to enhance the body's natural system of dealing with tissue damage. The problem is treated at the cellular level by electrotherapy, and soft tissue and joints are also given manual manipulation. In general, the pattern of recovery for tendon and muscle injuries is passive stretching to restore the lost flexibility, followed by specific strengthening exercises concentrated on the injured muscle group, aided by neuromuscular stimulation. The final stage is that of functional exercise in which the injured muscle group works in coordination with its surrounding muscles and normal patterns of movement are regained. For joint injuries the pattern of rehabilitation usually consists of strengthening exercises for the surrounding muscles to regain stability, and exercises to maximise mobility leading to the final stage of functional dynamic exercise.

< previous page

page_257

next page >

< previous page

page_258

next page > Page 258

No injury or loss in performance should be ignored the sooner the problem is treated the more satisfactory the end result will be. Nature alone will not allow the maximum performance to be achieved as there may be restricted mobility, loss of full power and decreased function. Techniques Used in the Treatment of Injury Most of the machinery that is used in sports therapy is readily obtainable, but incorrect use of this equipment can be very harmful. The horse owner should only use therapeutic machines with the guidance of skilled and trained therapists or veterinary surgeons. Do not assume that because one technique worked for a certain injury that the same technique is suitable for a different type of problem, and remember that even though a horse may have come sound the injury is unlikely to have healed completely. Hot and Cold Treatment In the initial stages of an injury the application of cold will help control the inflammatory reaction and relieve pain. The cold treatment should be applied frequently for short periods and may take the form of proprietary cold dressings and bandages, a bag of frozen peas or water wellies the latter having also a massaging jacuzzi action. Water wellies are tall boots, encasing the horse's leg up to above the knee: water is forced into the boot, having a cooling and massaging effect. Ice should never be applied directly to the horse's skin. Once the initial acute phase of the injury has passed, hot and cold therapies can be alternated to increase the blood flow to the affected area, bringing with it the elements essential for healing. Massage and Passive Stretching Massage is a very valuable area of physiotherapy, and probably the only treatment in which the layman can do no harm. Pain can be effectively relieved and the blood flow increased to an area by skilled massage, which can often achieve just as much as expensive therapeutic machinery. Massage can be used for tears, sprains, strains and spasms, filled legs and soft tissue problems, but a diagnosis should still be obtained before treatment. The underlying tissue is massaged either by the fingers, using a linear or circular movement, or by direct compression using the heel of the hand. Massage and soft tissue manipulation are used extensively by human

< previous page

page_258

next page >

< previous page

page_259

next page > Page 259

athletes both routinely during the training programme as well as before and after strenuous exercise to ensure that everything is functioning properly. The equine therapist can only communicate with their patient through their hands; they must explore the soft tissues thoroughly to detect the effects of exercise, to monitor the different stresses in the tissues and to interpret their meaning, even if there is no evidence of pain and lameness. Massage used like this can help prevent injury by ensuring that athletic function is not limited in any way. Massage creates friction which heats the skin and underlying tissues as they move over each other, dilates the blood vessels and improves the circulation from deeper tissues to these more superficial parts. Elasticity is restored and the waste products of exertion are cleared away. Muscles can be moved to prevent small adhesions from 'glueing' muscle bundles together. If allowed to form, adhesions could restrict muscle function. Passive stretching exercises can be used to move the horse's limbs through their normal range of movement to stretch the muscles and flex the joints. This is useful before working the horse; any limitations should be noted and the horse should be trained accordingly. Mechanical Massage Mechanical massage machines can be used as part of a planned treatment and rehabilitation programme to achieve better healing. They utilise a number of techniques including laser, magnetic field, ultrasound and muscle stimulation. Laser Therapy Laser stands for Light Amplification by Stimulated Emission of Radiation. In simple terms, the laser utilises the energy contained in white light. The key component of the laser is a sealed tube containing a mixture of two gases, typically helium and neon. When these gases are subjected to a high voltage, they emit a light of a specific and very precise wavelength. The light is reflected from end to end of the tube until only those rays that are parallel and in phase are permitted to escape from one end. This parallel beam of light is collected by optical coupling and passed into a flexible optic delivery tube and then to the stylus in the hand-held unit. As the beam is reflected along the length of the optical fibre, it loses its parallel quality and emerges from the tip of the stylus as a converging beam. Two main types of therapeutic laser are on sale to the general

< previous page

page_259

next page >

< previous page

page_260

next page > Page 260

public: those producing a visible red beam and those emitting an invisible beam in the infrared region. The gas from which the light source is created determines the visibility and wavelength of the light beam. The visible light has a wavelength of about 632 nanometres (nm) while the invisible beams are designed to produce six or seven different wavelengths in the range 660 to 950 nm. (A nanometre is one thousand-millionth of a metre.) As not all wavelengths are absorbed at, or penetrate to, the same depth, this variety is said to be more effective. Laser treatments can be pulsed or continuous and there is some debate as to which gives the best results; some machines can be switched from pulsed to continuous mode. Tissue is known to respond differently to different frequencies; pulsed beams are said to increase the possibility that tissue will be affected. Researchers do not yet understand all the factors which influence tissue and cell reactions, and there is insufficient evidence to claim conclusively that laser treatment will hasten repair, but many experts are confident that, if correctly used, the technique will assist healing. The dosage given is also critical; a minimum dose will have an effect while overdosing will inhibit physiological effects. Treatments can be as short as 1 minute but are usually longer. Read the instructions and never over-treat. Laser can also be used to perform acupuncture, stimulating acupuncture points rather than directly treating the affected area. There are seven classical emission frequencies used in laser therapy, ranging from 73 to 4672 Hz. Acute injuries are treated with low frequencies, wounds with middle range frequencies, while chronic problems may need 2000 to 3000 Hz. The very highest frequency is used for pain relief and acupuncture. There are four main effects that lasers are said to produce: to lessen the pain to reduce inflammation to accelerate the healing process to have a stress-managing effect. The relief of pain is very important and use of a laser may be better than giving pain-killing drugs with their possible side-effects. However, lasers can ease pain so that the rider thinks that the horse has recovered sufficiently to start work or to have work levels increased, but healing may not be complete and more damage will be done. Lasers should be used as part of a carefully monitored programme which will ensure that pain relief is permanent and healing is complete. Pain is relieved by interfering with the transmission of pain nerve impulses and by the release of endorphins.

< previous page

page_260

next page >

< previous page

page_261

next page > Page 261

It is claimed that inflammation in damaged tissues is reduced by the release of histamines, increased lymphatic drainage and reduced secretion of prostaglandins. Histamines are naturally produced substances which dilate blood capillaries, allowing increased blood flow to and from the area. Prostaglandins are body chemicals that cause smooth muscle contraction and hence constriction of blood capillaries; they are among the causes of pain experienced during a headache. The healing process is stimulated through greater cellular activity and division, there is greater tissue granulation, collagen production and an increased rate of epithelialisation, the laying down of epithalial tissue, e.g. skin. Lasers can be used to treat tendon and ligament injuries, superficial bone and joint injuries, open wounds and old fibrous injuries. In the case of open wounds it has been claimed that the prompt use of lasers inhibits the formation of proud flesh and thus assists effective healing. However, laser therapy should never be started until a veterinary diagnosis has been obtained; if the wrong ailment is being treated the horse may suffer. Ultrasound Ultrasound therapy can be one of the most effective forms of treatment and has produced outstanding results at the initial stages of repair. Ultrasound can also be one of the most dangerous. Ultrasound waves are sound waves with a pitch above the upper limits of human hearing, produced by making a solid object vibrate at very high frequency. These waves are absorbed at a molecular level, creating a micromassage effect; the cells of underlying tissues are made to vibrate rapidly. The flow of blood and lymph is increased, thereby reducing inflammation and giving some pain relief. Ultrasound can reduce muscle spasm, increase the elasticity of scar tissue, stimulate blood circulation and cellular activity, and improve the quality of tendon repair, providing that treatment is given in the 2 weeks immediately after injury. Treatment times and frequency settings depend on the type of injury. The frequency used is always very low, using a pulsed rather than continuous beam, to reduce the heat generated, which could otherwise be detrimental to the healing tissue. As the effects of the machine remain unseen, a common temptation to the untrained is to increase the frequency or treatment time. The vibrations of ultrasound can literally cause cells to implode they collapse and die. It is also possible to crack bone with ultrasound. Thus the choice of frequency

< previous page

page_261

next page >

< previous page

page_262

next page > Page 262

requires an in-depth knowledge of tissue types and the effects of ultrasound. Conditions exist where ultrasound would be actively harmful; if infected, the tissue may break down and the infection increase in severity. The use of ultrasound should be limited to specific injuries after consultation with a veterinary surgeon or qualified equine therapist. Magnetic Field Therapy Magnetic field therapy (MFT) is another form of treatment where the effects on tissue are far from being sufficiently understood or researched. Originally it was designed for use in humans and proved successful for increasing the rate of fracture healing; it accomplishes this by creating a specific magnetic flux across bone which is in tune with the cells' magnetic forces. However, its analgesic effects are such that it can substantially mask pain, sufficient to hide even a fracture of the pelvis. MFT can be useful for bruising, fractures and joint and ligament injuries. Manufacturers have claimed that acceptable results have been produced in the early stages of mild arthritic conditions, providing that the degenerative changes are not irreversible. Magnetic foil pads and boots can be used to treat minor problems quite safely by the horse owner and may well justify a place in the competition horse's first aid box. Machines that provide pulsed or static MFT should be used under the supervision of an expert, and the manufacturers' instructions and suggested treatment times should be carefully observed. The large machines use a pulsing magnetic field which is set up around the area to be treated by adaptors which may be held in position by velcro pads on a cotton sheet. The time, frequency and intensity of the field are all variable, but more research is needed to establish how these factors interrelate. The magnetic field is said to increase the cells' metabolic rate and accelerate the healing process; undoubtedly the blood circulation in superficial tissue is increased and this will have an effect on deeper tissues. Faradism and Muscle Stimulators. The electrical stimulation of muscles works on the principle that an electric current can stimulate a motor point and so cause a contraction of that muscle. This increases circulation and is useful where muscles have atrophied, are weak or have become imbalanced so

< previous page

page_262

next page >

< previous page

page_263

next page > Page 263

that the horse's movement suffers. The faradic machine is one of the more commonly known devices; it uses a variable alternating current which gently exercises the muscle without effort by producing a changing rhythm of contractions, and it can be used to restore muscle wasted due to lack of use, damage or disease. Good results can only be achieved if it is used properly, i.e. if the active electrode is placed over the motor point the activating area of the muscle. Manufacturers claim that faradic machines 'can be used by an unqualified person possessing an adequate knowledge of anatomy'. However, best results will be obtained if the operator has an understanding of muscle fibres, muscle function singly and within groups, nerve supply, musculotendinous junctions and muscle types, i.e. superficial, deep, postural, active and approximal. It must be appreciated that there is little or no benefit in stimulating groups of muscles, thus increasing their strength, if the result is an imbalance in muscle activity. A working area of the body which is at a mechanical disadvantage is placed under considerable strain. Being able to detect these subtle differences takes experience. Faradism is now an outdated method of stimulating muscle contractions and one limitation is an unpleasant skin sensation which becomes intolerable if deep muscles are to be reached. Muscle stimulators now available treat with more accuracy and comfort, and some are able to create a naturally occurring type of muscle contraction a muscle ripple. Some machines can reach deep muscle groups, even those beneath the pelvis, with comfort. Some musclestimulating machines can be used to contract muscles only, while others can be used on a variety of tissues to increase cell activity and to restore ionic balance in damaged tissue. Electro-Vet and Ionicare Electro-Vet and Ionicare are similar systems; success is claimed for various leg and muscle injuries, but there is no substantiating laboratory proof or relevant papers supporting these claims. They are said to be useful for treating bruising, filled joints, windgalls and mild muscle weaknesses. When an injury occurs, the ionic charge of surrounding normal cells becomes electrically out of balance and this inhibits their function. As electrotherapy has become increasingly understood, it has been suggested that a low frequency current passing through tissue influences cells and allows them to resume normal function.

< previous page

page_263

next page >

< previous page

page_264

next page > Page 264

Selection of Treatment Correct diagnosis is fundamental to the recovery of any physical problem; treatment by physiotherapy can then be used to assist the healing process. Buying or hiring complex therapeutic equipment is best left to the professionals who can use it to best effect. However, if circumstances are such that equipment is being used by the layman, then professional advice is needed and close monitoring is essential if the treatment is to be beneficial. Table 20.1 provides a guide to choosing the most appropriate treatment. Table 20.1 Guide to selecting a suitable treatment. Injury

Treatment

Inflammation

Cold, laser, ultrasound, MFT, Electro-Vet

Pain

Cold, laser, ultrasound, MFT

Tendon and ligament damage

Laser, ultrasound (if given in the 2 weeks after injury), MFT

Strains

Massage, laser, MFT

Muscle spasm

Massage, laser, Electro-Vet

Filled legs

Massage

Wounds

Laser

Bony enlargements

Laser

Important Always ask for professional advice: otherwise you could make the problem worse by misdiagnosis and using the wrong treatment. MFT, magnetic field therapy

Swimming Swimming can be a very useful part of a training programme and can also be used in a rehabilitation programme. The horse which needs to maintain muscle, respiratory and circulatory fitness but is temporarily lame, one that cannot withstand the stress of a hard traditional training regime, overweight horses, those suffering from the effects of wear and tear, and horses with conformation defects will all benefit from swimming. The absence of weight on the limbs means that movement under

< previous page

page_264

next page >

< previous page

page_265

next page > Page 265

water is less painful and that joints can move freely through their full range of movement. If a joint does not move it will deteriorate and become a problem even if it was not the original cause of lameness. A horse which is in pain will develop uneven musculature as it compensates to avoid using the area that hurts. Swimming will keep the muscles in use and help build balanced muscles which may even adjust uneven action. A horse on box rest cannot get rid of its surplus energy and, when brought back into work, may well become overexcited and damage unfit muscles. Swimming during the recovery period will exercise the horse and maintain its muscle tone. Stale or overtrained horses and horses with psychological difficulties have all benefited from swimming, and it can be included in the training programmes of horses as diverse as racehorses and police horses. Swimming As Part of a Fitness Programme The horse should swim only for a short time initially and it must learn to swim correctly. If it is tired or frightened the horse will be tense and swim with tight muscles and poor technique. Bad techniques produce bad results and have not given swimming horses a good reputation. Boots should be worn all round, with overreach boots in front to protect the limbs. Heart rates should be taken before and after swimming, and the horse's recovery noted and compared to previous results, just as with an Interval Training programme. In this way the horse's workload can be built up gradually to produce the best results. Once the horse has become accustomed, it will swim with a heart rate of between 140 and 170 beats per minute, which is equivalent to a 500 m/min canter and is very useful aerobic exercise. This means that three 3-minute swims can replace one canter session from week 9 of the training programme onwards. The respiration rate, as in galloping, synchronises with the leg movements of the horse, and is usually about 18 to 24 breaths per minute during swimming. However, this may go up to 42 to 60 breaths per minute after the horse leaves the pool. As with canter work, the horse should be allowed to recover until its heart rate falls below 100 beats per minute before being asked to perform the next period of swimming. After the swim the horse should be scraped as dry as possible, have a cooler thrown over it and walked until it is dry, for at least 15 minutes. Anaerobic work with heart rates over 200 can be achieved by using

< previous page

page_265

next page >

< previous page

page_266

next page > Page 266

tethered or restricted swimming and should only be carried out for short periods. If the horse is made to swim for short periods at varying speeds with short recovery periods it will develop muscles for work, not just for keeping it afloat. Water Walks Swimming can be criticised for being artificial, in that it may only teach horses to win swimming races! Water walks, however, provide good exercise and remedial treatment. Walking is a good exercise in itself, but walking through water is harder work with the advantages of reduced concussion and cushioning while still bearing weight. Complementary Therapies As we move away from artificial drug-oriented therapy in human health regimes, so we see the same trend in helping the horse find a way to health. Complementary therapies look at the whole animal the environment, work levels and diet as part of the illness. Complementary medicine is also about prevention, seeking to find out why an individual is more susceptible to illness and how that susceptibility can be reduced to bring the body back to its natural state of health. Homeopathy and acupuncture are two therapies which are being used more commonly in treating horses, sometimes with very good results. Homeopathy Homeopathy is a central complementary therapy: formulated and developed in the nineteenth century, it is based on the principle that like cures like. Homeopaths believe that the body is capable of healing itself, given the correct help. The help offered is two fold an accurate reading of the 'disease picture' (the patient's signs and symptoms) and the careful prescription of minute quantities of the remedy which would induce such signs and symptoms in a healthy body. These remedies are designed to stimulate and mobilise the body's own defence systems, enabling it to fight off the disease without the use of prescribed drugs which may have side-effects. Common minor problems are easily treated with homeopathy, as shown in Table 20.2. Homeopathic remedies are commonly available from the local chemist who may also be able to advise on their use. The horse-owner can diagnose and treat the minor ailments outlined here without consulting a homeopathic specialist, but if the condition

< previous page

page_266

next page >

< previous page

page_267

next page > Page 267

Table 20.2 Homeopathic remedies for common problems. Problem

Homeopathic remedy

Bruised muscles

Arnica 30 taken internally Arnica ointment to unbroken skin

Bruised bones and strained ligaments

Ruta 6 taken internally 4 times a day Ruta graveolens ointment externally

Cuts and grazes

1 part Calendula-Hypericum tincture to 10 parts tepid water Calendula ointment

Bites and stings

Calendula-Hypericum tincture Ledum or Hypericum tincture Cantharis 6 or Apis 6 if skin swollen and burning

does not respond rapidly to treatment expert homeopathic advice should be sought. Homeopathic treatment of more complex problems needs specialist expertise. Acupuncture To the acupuncturist the body is a self-healing entity, and acupuncture works by balancing the body's energy to enable the self-healing process to take effect. The acupuncturist controls the flow of energy by inserting fine, sterile needles at specific points along the energy pathway or meridian. If there is an obstruction to the energy flow along a meridian, sooner or later the animal will show signs of disease. If the acupuncturist manipulates the body's energies at the acupuncture points, the outcome of a disease or disorder can be affected. Acupuncture can be used to treat a wide range of ailments and disorders, and is now being used to treat horses for bone, muscle and joint problems. Cold laser is a useful way of stimulating the horse's acupuncture points and has been used with some success. The Eastern theory is that if the body is balanced within itself then there will be no chance for an illness or disorder to occur and the cold laser can be used to treat muscular, intestinal and inflammatory conditions via acupuncture, rather than directly treating the affected area.

< previous page

page_267

next page >

< previous page

page_268

next page > Page 268

Using Physiology to Get Horses Fitter. As we learn more about the exercising horse and how it functions, and as equine sports therapists become accepted as important members of the performance horse's team, we see that they have a role in getting the horse fit as well as helping the horse recover from injury. Centres now specialise in pre-conditioning therapy to help the horse withstand the stress of a training programme. This pre-season training is designed to stimulate the horse's metabolism so that when it is asked to work, the horse can co-ordinate and balance its muscular activity and internal body processes. For example, one aspect of this therapy is the stimulation of the circulation of the blood through the tissues using electromedical techniques such as ultrasound, faradism and magnetic field therapy. By the time the horse goes into its conventional training programme and the muscles demand oxygen for energy production, the pre-conditioned circulation should thus have become accustomed to respond correctly and therefore avoid injury.

< previous page

page_268

next page >

< previous page

page_269

next page > Page 269

CONCLUSION The theory and practice of getting horses fit is a vast subject, and no book can hope to do more than skim the surface. The aim of this book has been to make the owner/trainer/rider more aware of the systems of the horse's body and how these systems cope with exercise and adapt to training. A description has been given of various training methods, both traditional and modern, together with methods of assessing fitness. Using this new knowledge, trainers can select the method that suits them and their horse best. It must be emphasised that one method may suit one person but not another; horses, too, are individuals and must be treated accordingly. A degree of flexibility is vital in any training programme, and this is recognised to a greater extent in modern training methods than in traditional ones. The trainer must be aware of the competitive goals and the standard of fitness necessary to achieve them. Overfitness and overfeeding can cause as many problems as lack of fitness, particularly for the inexperienced or younger rider. Training horses cannot be learned out of a book, and there is no substitute for experience. However, it is the authors' hope that this book will make gaining that experience a little easier for both horse and rider.

< previous page

page_269

next page >

< previous page

next page >

page_270

Page 270

APPENDIX: A GUIDE TO SPEEDS AND PACES Gait

Speed km/h

m/min

m.p.h.

Brisk walk

6

100

3.7

Slow trot

9

100

5.5

Medium trot

12

200

7.5

Fast trot

15

250

9.3

Slow canter

18

300

11.2

Medium canter

21

350

13.0

Brisk canter

24

400

14.8

Hand gallop

27

450

16.8

Medium gallop

30

500

18.7

Fast gallop

36

600

24.3

< previous page

page_270

next page >

< previous page

page_271

next page > Page 271

GLOSSARY A Abdomenbody between chest and pelvis. Acetyl CoAa carrier for acetate, important in the transfer of acetate from pyruvic acid into the tricarboxylic acid cycle. Acidosisdisturbance of acidbase balance due to any acid other than carbon dioxide. Adenosine diphosphatelow energy compound. Adenosine triphosphatehigh energy compound involved in muscle contraction. Adrenalin: substance secreted by medulla of adrenal gland. Causes rise in blood pressure, dilation of pupils, inhibited movement of the alimentary tract, sweating, fast breathing and the formation of glucose from liver glycogen. Aerobic thresholdthe point at which lactic acid builds up in tissue due to anaerobic respiration. Albumin serum protein. Alkalosis a decreased hydrogen ion concentration, leading to an elevated pH of the blood. Normal arterial blood pH is 7.5. Anaerobicin the absence of oxygen. Anterior mesenteric arterysupplies small intestine, caecum and part of colon. Aortatrunk of main artery beginning at base of left ventricle. Ascaridnematode parasite; whiteworm. Aspergillusgenus of fungi, including several common moulds. Atrial fibrillationcondition in which the heart beats irregularly due to rapid and ineffectual contractions of first chambers. Causes reduced performance. Atrio-ventricular valvesthose guarding opening between first and second chamber (atrium and ventricle) on left and right sides of heart (bicuspid and tricuspid valves). Atrium (auricle)first chamber of the heart. Azoturiapainful condition of large muscle masses of back and behind quarter. Also known as setfast; tying-up.

< previous page

page_271

next page >

< previous page

page_272

next page > Page 272

B Barscontinuation of wall of foot; turns inward at heel to run parallel with frog. Basophiltype of white blood cell identified by dye-staining at post mortem. Biochemistrythe science of organic reactions taking place within the body. Biological valuethe amino-acid make-up of the protein related to its nutritional value. Biscuspid valvevalve separating left atrium and left ventricle of heart. Bloodfluid circulating in arteries, capillaries and veins and driven by pumping action of the heart. Blood testexamination of blood samples in laboratory to aid diagnosis of disease. Bonehard substance making up body's skeleton. Bronchiolitisinflamed bronchioles when tubes become full of exudate. Bursasac or cavity filled with fluid at places where friction is likely to occur. C Caecumlarge comma-shaped sac between small intestine and colon. Calcifyto become impregnated with calcium, i.e. bony. Calciummineral required for bone and tooth formation. Cancellousspongy (used in connection with bone tissues). Carbohydratefood substance found in vegetable and animal tissue. Carbon dioxidea gaseous waste product of aerobic respiration. Carbon fibre implanta treatment for damaged tendons of the lower limb. Cardiac musclemuscle of the heart. Cellulosecarbohydrate making up part of plant cell wall. Circulatory systemblood, blood vessels, heart, lymph and lymphatic vessels. Compact bonedense outer layer of bone. Coriummodified vascular tissue inside horn or hoof. Can be likened to bed of human nail. Coronet bandband at the top of hoof and lower part of pastern; seat of hoof growth. Creatine phosphatea source of energy contained in limited amounts in muscle cells. D Deep digital flexor tendontendon of the lower leg attaching to the pedal bone. Dental systemthe teeth and associated structures.

Detoxifyto render poisons harmless.

< previous page

page_272

next page >

< previous page

page_273

next page > Page 273

Digestible energya measure of the energy value of feedstuffs, measured in megajoules. Digestive systemthe organs and glands involved in the digestion of food. Digital cushionfibro-elastic fatty pad at back of foot. E Egg counta count of parasitic worm eggs in the faeces. EIPHExercise Induced Pulmonary Haemorrhage bleeding from the lungs during or following exercise. Elastic zonerange of stress that bone can accommodate by stretching. Electrocardiograma graphic tracing of the electric current produced by the heart muscles. Electrolytesubstance present in the body fluids which is capable of conducting electricity in various body functions, such as nerve impulses, oxygen and carbon dioxide transport, and muscle contraction. Emphysemaan abnormal accumulation of air in tissues or organs, e.g. overinflation of the alveoli of the lungs. Endotoxina poison produced within the body. Enotenoninternal tendon covering supplying blood vessels and nerves. Enzymea protein which catalyses (helps cause or accelerate) a chemical reaction without being consumed in the process. Eosinophiltype of white blood cell. Epiglottissmall flap of cartilage which covers entrance to voice box. Epiphyseal'growth' plate; the cartilage separating the epiphysis from the shaft of a bone. Epiphysisa part of a bone, especially at the end of a long bone, which develops separately from the shaft of the bone during the growth period. During this time it is separated from the main portion of the bone by cartilage. Epistaxisnosebleed. Epitenonexternal covering of the tendon. Erythrocytered blood cell which transports oxygen. Excretionthe act of eliminating the body's waste materials. Exhalationas expiration. Exhaustioncomplete inability to continue work. Exostosisa benign bony growth projecting outward from the surface of a bone. Expirationthe act of expelling air from the lungs. Extracellular fluidbody fluid contained between the cells and bathing them.

< previous page

page_273

next page >

< previous page

page_274

next page > Page 274

F. Fartleka training method. Fatwhite or yellowish material laid down around, or in, various organs and muscles of the body. Also part of diet comprising fatty acids and glycerol, high in feeds such as linseed. Fatiguetiring of the body systems associated with exercise. Fatty acidseach fat molecule consists of three fatty acid chains attached to glycerol, which are broken down to form carbon dioxide and water via the tricarboxylic acid cycle. Fermentationenzymatic decomposition. Fibreinsoluble carbohydrate, such as cellulose, making up an essential part of the diet. Fibrillationrapid contraction, as in atrial fibrillation. Fibrinthe essential fibrous protein portion of the blood. Fibrinogena protein in the blood essential to the clotting process. Fibroblasta specialised body cell. Fibrous adhesiona fibrous band or structure by which parts abnormally adhere. Firingapplying a heated firing iron to a leg to produce a severe inflammation; used to treat chronic or subacute inflammations of the joints, tendons and bones. Floatingthe act of filing down the teeth to remove sharp edges. Foraminanatural openings or passages in the body. Forceplatea plate used for recording the forces on a horse's foot as it moves. Founder stancethe typical stance of a horse with laminitis in which the animal will try to take as much weight as possible off its front feet. Frogthe band of horny substance in the middle of the sole of a horse's foot, dividing into two branches and running towards the heal in the shape of a 'v'. G Gad-flythe warble-fly. Gait analysisfilming and analysing each portion of the horse's gait. Gaseous exchangethe exchange of oxygen from the lungs for carbon dioxide in the blood. Gastricpertaining to the stomach. Germa pathogenic organism. Glanda body organ whose function is to secrete a substance useful to the animal. Glandsaggregations of cells, specialised to secrete and excrete materials.

Globulinsblood proteins.

< previous page

page_274

next page >

< previous page

page_275

next page > Page 275

Glucagona hormone released by the alpha cells of the Islets of Langerhans (in the pancreas) which raises the blood sugar by stimulating the breakdown of glycogen to glucose in the liver. Glucocorticoidshormones from the adrenal cortex. Glucosea sugar which is a principal source of energy. Glycerolfat consists of three fatty acids attached to glycerol. Fat can be broken down into its constituents by glycolysis, and releases energy in the process. Glycogenthe body's main carbohydrate-storing substance. Glycogen sparingwhen the body uses fat as an initial source of energy, conserving glycogen stores. Glycolysisthe breakdown of glycogen to provide energy within the body. H Haematomaa localised collection of blood, usually clotted, in an organ, space or tissue, due to a break in the wall of a blood vessel. Haemoglobinthe oxygen-carrying protein pigment of the red blood cells. Haemorrhagebleeding. Haversian systemsthe systems into which the bone cells are organised. Heartmuscular organ with four chambers which pumps blood through system of vessels. Heart rate monitora device for measuring the heart rate of a working horse. Heat exhaustionhyperthermia; circulatory collapse and shock caused by high environmental temperature, high humidity and poor ventilation. Heatstrokemore serious than heat exhaustion; sweating usually stops. Often fatal. Heavesa respiratory ailment; forced expiration resulting from rupture of the alveoli in the lungs. Caused by allergies and dust. Histaminea chemical compound which dilates capillaries and constricts the smooth muscle of the lungs. Hoofhorny casing of foot. Hormonea chemical substance, produced in the body by an organ, which regulates the activity of another specific organ. Hyperthermiaheat exhaustion or heatstroke. Hypertrophythe enlargement or overgrowth of an organ. I Ileumthe distal portion of the small intestine extending from the jejunum to the caecum.

< previous page

page_275

next page >

< previous page

page_276

next page > Page 276

Impactionthe condition of being firmly lodged or wedged. Incisorfront tooth specialised for biting. Inflammationa condition where tissues show pain, heat, redness, swelling and exudate as a reaction to injury. Influenzaan acute viral infection involving the respiratory tract. Ingestioneating. Inhalationdrawing air into the lungs. Inspirationas inhalation. Insulina protein hormone which is produced by the beta cells of the Islets of Langerhans of the pancreas. Reduces blood sugar levels by making cells more permeable to glucose. Intercostalbetween ribs. Interval traininga method of getting horses fit; a specific period of work is given, followed by a specific period of rest. Intestinalpertaining to intestines. Intestinal florathe bacteria normally present within the intestines. Intracellular fluidfluid found inside cells. J Jejunumthe middle portion of the small intestine, extending from the duodenum to the ileum. L Lactic acidan organic acid normally present in muscle tissue. Produced by anaerobic muscle metabolism. Laminaemembrane or sheet containing fine leaf-like projections. Laminitisinflammation of the laminae of the foot. Larvaan early developmental stage of a worm. Larynxthe voice box. Lesionan abnormal change in the structure of a part due to injury or disease. Letting downreducing a horse's fitness in a gradual and controlled manner. Leucocyteswhite blood cells or corpuscles. Ligamentband of fibrous tissue that connects bones or cartilages. Ligninan indigestible structural carbohydrate found in plant cell walls. Lipidan organic substance containing fat, which is an important component of living cells. Lungwormnematode parasite living in the air passages of the lungs.

Lympha transparent yellowish liquid containing white blood cells and derived from tissue fluids. Lymphangitisinflamed lymphatic vessels and lymph nodes, especially in legs.

< previous page

page_276

next page >

< previous page

page_277

next page > Page 277

Lymphatic systema system of vessels containing and transporting lymph. Lymphocytea type of white blood cell. Lysinean essential amino acid. M Maintenancea state where the animal is fed enough to maintain life and all body functions without gaining or losing weight. Marrowred or yellow soft material in central cavity of long bones. Megajouleunit in which the energy value of a foodstuff is measured; this is expressed as megajoules of digestible energy per kilogram (MJ DE/kg). Membranea thin layer of tissue which covers a surface, lines a cavity or divides a space or organ. Mesenterya fold or membrane attaching various organs to the body wall. Metabolismthe total physical and chemical activities of an animal. Methioninean essential amino acid. Micronutrientsnutrients needed in minute amounts, e.g. minerals and vitamins. Micro-organismsminute microscopic organisms such as bacteria, viruses, moulds, yeasts and protozoa Micropolyspora faenia fungus whose spores can cause an allergic reaction. Mineralinorganic substances, some of which are essential for the maintenance of health, e.g. iron, iodine, calcium. Mitochondriathe powerhouses of the cell where energy is produced. Molartooth adapted for grinding. Monday morning diseaseazoturia; painful movement and 'tying-up' of back muscles. Monocyteswhite blood cells active in fighting subacute infections. Monosaccharidethe most simple form of sugar, e.g. glucose, fructose. Mucusthe free slime of a mucous membrane; composed of the secretions of glands. Murmura periodic sound, of short duration, of cardiac or vascular origin. Muscle biopsythe removal of a sample from living muscle using a specialised needle. Mutanta permanent change in the characteristics of an organism. Myoglobina protein contributing to the colour of muscle and acting as a store of oxygen. N Nasal passagesthe airways of the head, leading from the nostrils to the trachea.

< previous page

page_277

next page >

< previous page

page_278

next page > Page 278

Navicular bonea small bone in the foot of a horse. Nematodeany of a group of roundworms which are mainly internal parasites. Nervescordlike structures, visible to the naked eye, comprising a collection of nerve fibres which convey impulses between a part of the central nervous system and some other region of the body. Nervous systemthe system of nerves throughout the body. Neutrophila white blood cell type. Nostrilentrance to the respiratory tract. O Organa somewhat independent part of the body that performs a special function or functions. Osmosisdiffusion through a semipermeable membrane. Osseleta bony growth on the inner aspect of a horse's knee or on the lateral aspect of the fetlock. Ossifyto change or develop into bone. Osteitisinflammation of a bone. Osteoblastscells involved with bone destruction. Osteoclastscells involved with bone formation. Oxidativea reaction using oxygen. Oxygencolourless, odourless gas inhaled from the atmosphere. Oxygen debtis incurred at maximal exercise levels and is the oxygen used afterwards to oxidise accumulated lactic acid. P. Pacemakerthe specific area of the heart that controls the heartbeat. Packed cell volumeproportion of blood cells to plasma; expressed as a percentage. Parasitea plant or animal which lives upon or within another living organism at whose expense it obtains some advantage. Pedal bonebone inside hoof. Periostitisinflammation of the periosteum (bone covering). Periopleexternal, shiny, water-repellent covering of the hoof. Phagocyteany cell that ingests micro-organisms or other cells and foreign particles. Pharynxthe sac between the mouth and the oesophagus. Physiologythe branch of biology which deals with the normal functions and activities of life or living matter.

Pinch testa simple test to assess dehydration by pinching a fold of skin on the neck. Plasmathe liquid portion of the blood. Poulticea moist dressing applied hot to a given area in order to create moist local heat or counter irritation.

< previous page

page_278

next page >

< previous page

page_279

next page > Page 279

Proteinone of a group of complex compounds which contain nitrogen and are composed of amino acids. Protozoasingle-celled organisms. Pulmonarypertaining to the lungs. Pulserhythmic throbbing of an artery which may be felt by the finger. Caused by blood forced through the vessel by contractions of the heart. Pusa liquid inflammation product made up of white blood cells and dead tissues. Pyruvic acidthe end product of the anaerobic breakdown of glucose which gives rise to lactic acid. Q Quarterspart of the wall of the foot between the heel and the toe. Quiddingwhen the horse spits out partially chewed food. R Raspingfiling the teeth with a rasp to provide dental care. Rationa carefully designed allocation of food. Recovery ratethe time in which the horse recovers from exertion; measured by pulse and respiration rates. Red blood cellshaemoglobin-carrying cells in the blood. Remodellingthe process undergone by bone which has been put under stress. Renal arterysupplies the kidneys with blood. Reproductive systemthe organs involved with conception, gestation and birth. Respiratory ratenumber of breaths in one minute. Respiratory systemthe airways and lungs. Rhinopneumonitisinflammation of the nasal and pulmonary mucous membrane (equine herpes virus 1). Ricketsdisease of young horses characterised by lack of calcium in bones. Ringbonebony enlargements below fetlock. Roughing-offgradually adapting the horse to living outside rather than being stabled. Rubefacientdrug or other substance that increases blood flow. S Scouringdiarrhoea; loose, runny faeces. Secreteto produce and give off cell products. Semilunar valveshalf-moon shaped cups forming a valve which guards the exits of the heart.

Serumclear fluid which separates from red blood clot, i.e. whole blood minus cells and fibrinogen.

< previous page

page_279

next page >

< previous page

page_280

next page > Page 280

Sesamoid bonessmall bones inserted into tendons where pressure occurs. Setfastsee azoturia. Shaftmain part of long bone. Skeletal musclestriated or voluntary muscle responsible for movement of the skeleton. Skeletal systemthe body's framework of bone and cartilage. Small airway obstructionblockage of bronchioles of lungs due to excess mucus production and muscle contraction. Smooth musclenot under voluntary control; found in walls of gut, bladder and uterus. Soft palatemembrane of muscles separating mouth from pharynx. Soleundersurface of foot. Sore shinsinflamed lining of cannon bone. Spavincondition of hock joint or surrounding area. Spleena blood storage organ situated near the stomach. Splintcondition of the splint bone. Spongy bonesoft bone. Starchthe form in which plants store glucose. Stethoscopeinstrument for listening to heart and gut sounds. Stressforcible exerted influence or pressure. Strongyleredworm. Subclinicalwhere the horse is suffering from disease but shows no clinical symptoms. Sugarcarbohydrate found in vegetable and animal tissue, e.g. starch, sucrose, lactose. Sweatsalty fluid; evaporation from skin causes cooling of the body. Synchronous diaphragmatic fluttera condition where the heart appears to be beating in the flanks, indicating severe fatigue. Also known as thumps. Synovial fluidfluid found within joint; has a lubricating function. Systemic circulationthe circulation of blood through the body, excluding the lungs. Systolecontraction of the heart chambers. T Temperature38°C (100.5°F) in a healthy horse. Tendona fibrous cord of connective tissue which attaches muscle to bone.

Tendon sheatha protective connective tissue layer surrounding the tendon. Tendon-splittinga method of treating damaged tendons. Tenoblastscells involved in tendon destruction.

< previous page

page_280

next page >

< previous page

page_281

next page > Page 281

Tenocytescells involved in tendon formation. Thermographya method of recording the heat of body surfaces. Thumpssee synchronous diaphragmatic flutter. Tissuean aggregation of similarly specialised cells united in the performance of a particular function. Tissue respirationthe production of energy in the cells. Toefront of hoof. Tracheathe windpipe. Tricarboxylic acid cyclethe aerobic breakdown of pyruvic acid to carbon dioxide and water with the creation of ATP. Tricuspid valvethe valve lying between the right atrium and right ventricle in the heart. Triglyceridea type of fat. Tropocollagenthe precursor of collagen. Tushescanine teeth found in male but not usually female. Tying-upsee azoturia. May also be result of a pulled muscle. U Ultrasoundcontrolled doses of high frequency sound (radiation) used for diagnosis and therapeutic treatment. Ureawaste product discharged in the urine. Contains nitrogen. Urinary systemthe kidneys, ureter, bladder and urethra. V Vaccinea suspension of attenuated or killed micro-organisms administered for the prevention or treatment of infectious disease. Vasoactivecauses blood vessels to constrict or dilate. Veina vessel through which the blood passes from various organs back to the heart. Vena cavathe major vein of the body. Ventriclesthe two larger, muscular chambers of the heart. Villitiny finger-like extensions of a membrane. Virusone of a group of minute infectious agents. Vitaminorganic substance necessary for normal metabolism. Vocal cordsmembranes, contained within the pharnyx, which allow vocalisation. W

Warm-upa period of exercise prior to work to prime the body systems. White linejunction of wall of foot with sole. Wolf teethvestigial pre-molars which may erupt and have to be removed.

< previous page

page_281

next page >

< previous page

page_282

next page > Page 282

INDEX A. Acidosis, 189 Acupuncture, 267 Adaptive response, 192 Adenosine Diphosphate (ADP), 30 Adenosine Triphosphate (ATP), 30, 182 Adenovirus, 116 Adhesions, 90 Adrenalin, 82, 188 Aerobic enzymes, 39 Aerobic metabolism, 27, 28 Aerobic threshold, 30 Alfalfa, 159 Albumin, 60 Alkalosis, 189 Alveoli, 23, 29, 110 Anaemia, 63, 107 Anaerobic metabolism, 27, 28, 30, 186, 265 Aorta, 44 Appetite, 170, 197 Arteries, 44 Arterioles, 44 Ascardis, 130 Ascorbic acid, 152 Aspartate aminotransferase (AST), 103 Aspergillus fumigatus, 109 Astrial fibrillation, 53

Atrophy of bone, 69 Avermectins, 133 B Barley, 153 Basophils, 56 Bathing, 9 Benzimidazoles, 134 Blisters, 95 Blood, 54, 55, 57, 107 sampling, 59 tests, 58, 117, 133, 202 Bodyweight calculations, 168 Bone marrow, 54, 65 Bone structure, 64 Bots, 132 Bowed tendon, 92 Bran, 156 Breathing, 25 Bronchi, 23 Bronchioles, 23 Bronchodilators, 112 Buffering capacity, 40 C Calcium, 147 Canter, 15, 205, 214, 240 Capillarisation, 46, 47 Capillary network, 44 Carbohydrates, 143 Cardiac cycle, 50 Cardiovascular system, 42, 241

Carbon fibre implants, 97 Cartilage, 65, 74 Cellulose, 143 Cereals, 152, 164 Chaff, 163 Check ligament, 87 Chromium, 149 Chronic obstructive pulmonary disease (COPD), 109 Circulation, 44 Circulatory system, 42 Clenbuterol, 112 Clipping, 201 Cobalt, 149 Cold laser, 267 Colic, 196, 226 Collagen, 87, 88, 89 Competitive trail rides (CTRs), 229 Complete cubes, 112 Compound feeds, 152, 164 Computers, 254 Conditioning, 3 Conformation, 91 Connective tissue, 87 Cooling, 146 Copper, 146 Corium, 75 Corticosteroid, 189 Cortisol, 189 Cortisone, 189 Creatine Phosphokinase (CPK), 60, 103 D

Degenerative change. 92 Degenerative joint disease (DJD), 75 Dehydration, 36, 63, 118, 121, 124, 196, 226 Dental system, 79 Deoxygenated blood, 44 Diastole, 50 Digestive system, 138 Digital cushion, 76 Dressage, 232 Driving horses, 241 E Egg counts, 133 Elastic zone, 72 Electrocardiogram, 48 Electrolytes, 104, 121, 122, 128, 147, 190, 196 Electro-Vet, 263 Endurance, 191, 227, 230 Energy, 28, 170, 171, 181

< previous page

page_282

next page >

< previous page

page_283

next page > Page 283

expenditure, 184 sources, 185 Eosinophils, 56, 60 Epiglottis, 21 Epiphyseal plate, 67 Epiphysis, 67 Epiphysitis, 73 Equine herpes virus, 113, 115 Equine influenza, 53, 114 Erythrocytes, 54 Ethmoid haematoma, 116 Event horses, 199, 249 Exercise induced pulmonary haemorrhage (EIPH), 116 Exertional rhabdomyolysis, 103 F Faradism, 262 Fartlek system, 247, 248 Fast twitch muscle, 34 Fatigue, 28, 35, 196 Fatigue zone, 72 Fat, 143, 191 Fat soluble vitamins, 150 Feeding, 138, 190, 196, 197, 203 Feed processing, 166 Fibrinogen, 54 Fibroblasts, 87 Firing, 96 Fitness, 212 Flat racers, 239

Forage, 158, 164 Forage concentrate ratio, 172 Force plates, 252, 253 Fracture, 73, 74 Frog, 76 G Gait analysis, 252 Galloping, 240 Galls girth, 13 Globulins, 60 Glucagon, 188 Glucocorticoids, 189 Glucose, 27, 186 Glycogen, 27, 36, 39, 186 Guttural pouch, 116 H Haematology, 61 Haematoma, 90 Haemoglobin, 26 Haversian systems, 69 Hay, 112, 158 Haylage, 112, 161 Heart, 42, 43 murmurs and arrythmias, 51, 53 rate, 48, 215, 249 score, 49, 254 size, 46 sounds, 51 Heartbeat, 50 Heat exhaustion, 123

Heat loss, 119 Heatstroke, 118 Heaves line, 111 High oxidative muscle, 34 Histamine, 112 Homeopathy, 266 Hoof structure, 75 Hormones, 186, 187 Hot treatment, 258 Hunters, 8, 16, 236 Hyperthermia, 36 I Inflammation, 94, 261 Injury, 90 Insulin, 186, 188 Interval training, 206, 211, 213, 218, 220, 231 Iodine, 149 Ionicare, 263 Iron, 148 Isoxsuprine hydrochloride, 101 J. Joints, 74, 241 Jump schooling, 237 L Lactate dehydrogenase (LDH), 103 Lactic acid, 28, 36, 38, 83, 207 Laminitis, 105, 252 Larynx, 22 Lateral cartilage, 77 Laser, 259 Learning, 6

Leucocytes, 56 Ligament injury, 98 Linseed, 156 Long-distance, 226 Low oxidative muscle, 33 Lucerne, 159 Lungs, 23, 119 Lungworm, 132 Lymphocytes, 56, 60 M Magnetic field therapy, 262 Maintenance, 166 Maize, 155 Manganese, 148 Massage, 94, 258 Mean corpuscular haemoglobin concentration, 60 Micropolyspora faeni, 109 Minerals, 146 Mitochondria, 31, 40, 187 Monday morning disease, 102 Monocytes, 56, 60 Muscle, 31, 185 Muscle biopsy, 32, 252 Muscle fibre types, 32 Muscular development, 29, 232 Muscle myopathy, 102, 103 Muscling-up, 31 Myofibrils, 31 Myoglobin, 31, 104 N

National hunt, 238 Navicular disease, 78, 98, 99, 100 Neurectomy, 101 Neutrophils, 56 Nostril size, 30 Nutrients, 142 O Oats, 153, 191 Osteitis, 73 Osteoblasts, 66 Osteoclasts, 70 Overload zone, 72 Oxygen, 54 Overuse injury, 257 Oxygen debt, 27, 30 P Packed cell volume (PCV), 54, 58, 59, 108 Parascaris equorum, 130 Periosteum, 65

< previous page

page_283

next page >

< previous page

page_284 Page 284

Periostitis, 73 Pharynx, 21 Phenylbutazone, 101, 103, 106 Phosphorus, 147 Physiotherapy, 256 Plasma, 54 Platelets, 54 Pleasure rides, 229 Point-to-pointer, 235 Polo ponies, 243 Post effort hyperventilation, 27 Potassium, 128 Preliminary work, 12 Pressure bandage, 94 Production, 167 Protein, 143, 167, 174, 175, 183 Proteoglycans, 75 Pulmonary capillarisation, 29 Pulmonary vein, 44 Pulse, 4, 48, 208, 228 Q Quidding, 81 R Racehorses, 235 Ration calculations, 176 Rationing, 166 Red blood cells, 54 Red blood cell count (RBC), 58 Red worm, 108

Respiration, 21, 24, 193, 226 Respiratory rate, 4, 26, 210, 228 Respiratory system, 21, 30, 109 Rhabdomyolysis, 103 Rhinopneumonitis, 115 Roughing off, 17 S Saliva, 145 Selenium, 104, 149 Sensitive laminae, 76 Serum, 54, 60 Setfast, 102 Shoeing, 9, 201 Show jumping, 233 Silage, 159 Skeletal muscle, 33, 102 Skin, 119, 120 Slow twitch muscle, 33 Small airway obstruction, 109 Small strongyles, 130 Speedtest system, 247, 248 Spleen, 57, 82 Sodium bicarbonate, 38, 189 Sodium chloride, 128 Sodium cromoglycate, 112 Soft palate, 21 Soyabean, 156 Stress, 6, 192 Starches, 142 Stethoscope, 209 Straw, 162

Strongyles, 129 Strongylus vulgaris, 129 Sugarbeet, 157 Sugars, 142 Supplements, 145 Sweat, 121 Sweating, 119, 195 Swimming, 215, 264, 265 Synchronous diaphragmatic flutter, 197 Synovial joints, 74 Systole, 50 T. Teeth, 9, 200 Temperature, 4, 119, 123, 208 Tendon healing, 93 Tendon injury, 97 Tendon splitting, 96 Tendon structure, 87 Thermography, 252 Thumps, 197 Tissue respiration, 26 TPR, 193 Trachea, 22 Training, effects of, 29, 46, 75 Training programme, factors influencing, 5, 182 Trotting, 14, 205 U Ultrasound, 251, 261 V Vaccination, 9, 115, 200

Valves, 45 Veins, 44 Vena cava, 42 Videos, 254 Vitamin A, 150 Vitamin B complex, 151, 187 Vitamin B12, 108 Vitamin C, 152 Vitamin D, 150 Vitamin E, 151 Vitamin K, 151 Vitamins, 150 W Walking, 12, 184, 204 Washing, 194 Water, 144, 194 Water soluble vitamins, 150 White blood cells, 56 Wolf teeth, 81 Worming, 9, 201 Z Zinc, 148, 187

< previous page

page_284