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4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 2June 1989NAME_________________________________________________________________________________________ ADDRESS_____________________________________________________________________________________ CLUB_________________________________________________________________________________________ 4-H HORSE PROGRAM HORSE SCIENCE This educational material has been prepared for 4-H use by the Cooperative Extension Services of the U.S. Department of Agriculture and State Land-Grant Universities in cooperation with the National 4-H Council and the American Quarter Horse Association. Trade or brand names used in the publications are used only for the purpose of educational information. The information given herein is supplied with the understanding that no discrimination is intended and no endorsement of products or breeds of horses by the Federal Extension Service or State Cooperative Extension Services is implied, nor does it imply approval of products or breeds of horses to the exclusion of others which may also be suitable. This material is published by the National 4-H Council, 7100 Connecticut Avenue, Chevy Chase, Maryland 20815. Programs and educational materials of National 4-H Council are available to all persons regardless of race, color, sex, age, religion, national origin or handicap. Council is an equal opportunity employer.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 3June 1989TABLE OF CONTENTS SUBJECT PAGE Behavior and Nature of the Horse4 Functional Anatomy and Action8 Unsoundness and Blemishes 11 Determining the Age of a Horse by Its Teeth14 Principles of Reproduction in Horses18 How Inheritance Works in Horses22 The Digestive System of the Horse25 Feed Nutrients 28 Feeds for Horses 31 Balancing Rations for Horses 34 Health and Sanitation Principles Important in Horse Care38 Disease Problems of Horses 40 External Parasites Affecting the Horse42 Internal Parasites of Horses 46
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 4June 1989 Since the time of ancient civilizations, the horse has servedFossil r emains have definitely established that the horse man well. He was first a war machine and that was his principaloriginated in North America beginning with eohippus. There may role until World War II. Likewise, the modern age has alsohave been an earlier five-toed ancestor but no fossil remains have relieved him of heavy duty as a beast of burden. But, the horse isso far been found. not yet about to be turned out to pasture. He is now serving man inThe third and final stage in the evolution of the horse into his a greater way than ever before as a means of recreation and escapepresent form (equus) also took place in North America but this from pressure and tension of present-day living. This greatspecies completely died out for reasons yet unknown. Fortunately, versatility is possessed only by the horse because of his (1)some of the population escaped to Asia during the Ice Age (about anatomical structure and function, (2) speed and endurance, andone million years after eohippus) by way of what may have been (3) fear of being hurt. The combination of these characteristics hasa land bridge in the Bering Strait area between Alaska and Siberia. made it possible for man to obtain performance from the horse farIt was, therefore, in Asia and Europe that the horse completed his beyond what is possible with any other animal.development and was domesticated. He did not return to North Century.ORIGIN OF THE HORSEThe horse had his beginning about 58 million years ago. His original home was in what is now the Great Plains area of North America. He evolved in three stages into his present form. The original ancestor (eohippus) was only about 12 inches high with four toes on each front foot and three toes each on each hind foot. He had a short neck, even teeth and was well-adapted to living in a forested and swampy environment. As the earth underwent geologic changes, the horse evolved into his second stage (mesohippus). Here he became larger (about 24" high), developed longer legs with only three toes on each foot. The middle toe was the largest. He also developed teeth suitable for grazing on the prairie and greater speed and endurance for finding forage and water and for protection and survival. These changes resulted from gradual adjustment to changing surroundings over millions of years. America until brought here by the Spaniards in the Sixteenth An important point is not how the horse developed into his present form but why. Besides having to go further in search of feed and water the horse also had to be able to run further and faster to escape his enemies. The horse is not the fastest animal on foot but possesses great endurance. The horse is, therefore, a creature of the open country and, to this day his first reaction to any strange or frightening object or situation is to panic and run away. This great fear of the unusual, plus the speed and endurance he has developed at the gallop, has made the horse a most valuable animal to man. But, it has also made him one of the most dangerous. Unlike a bull or lion, the horse seldom attacks directly. In an instant of fright, he can become completely unreliable and even pay no attention to his own safety. It might, therefore, be said that the modern horse must depend on man for his safety. The name eohippus or dawn horse is derived from the Greek word eos meaning dawn. The word horse comes from the Anglo-Saxon word hors meaning swiftness.ARABIAN QUARTER HORSE
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 5June 1989 closer than four feet. Likewise, the horse cannot see directlyFUNCTIONAL DIVISIONS OF THE HORSEThe Head and NeckThe head and neck serve the same purpose on the horse as on other animal species. So far as behavior is concerned, the most important feature of this portion of the horse's physical make-up is the eye. The eyes of the horse are rather large and are set wide apart on the sides of the head. This gives the horse monocular vision or the ability to see separate objects with each eye at the same time. The horse can also see anything behind him that is not narrower than his body. The horse does not have binocular vision except when interested or excited enough to lift his head and point his ears forward. In such case, the object must be some distance away and not downward and, therefore, can't see what he is eating. Neither can a high-headed horse see the ground directly in front of him. The horse, because of his ability to make a quick getaway, has no need for acute vision as does man. However, his ability to see objects on either side at once, and to the rear, has been a prime feature of his ability to survive. It is believed that horses do not all have perfect eyesight. No doubt, poor eyesight may have an effect on the behavior of certain horses. Shying at unfamiliar objects may be the result of faulty vision. By reason of being ever alert to danger the horse, through his eyesight, is very sensitive to quick movements. Any training procedure involving quick motions, such as roping or polo must, therefore, be started slowly and speeded up only after the horse has become familiar with the motion.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 6June 1989 The horse is suspended between his front legs. The front legsThe Forehand AssemblyAlthough no one foot or leg has a single function, the front feet and legs serve primarily to support the horse at rest. In motion the front feet and legs also pull the horse forward. The horse's center of gravity is located at a point about six inches behind the elbow. At rest the front feet and legs, therefore, support 9 to 10 per cent more weight than the hind legs. The healthy horse at rest cannot shift his weight from one front foot to the other but is continually shifting weight between his hind feet. Only when one front foot is injured does the horse shift weight to the other foot. As a result, the healthy foot may go bad from lack of exercise necessary to promote circulation. To keep his feet healthy the horse must, therefore, have plenty of exercise. Stabled, or closely confined, horses often become nervous and this may well be dueThis is the horse's powerhouse or propeller and serves to push to their feet hurting from lack of exercise.the horse along in motion. The hind feet and legs also offer support are not attached to the main skeleton by any joints, but only held in position by muscular structures. This provides the horse with an almost perfect suspension system for his body. This, along with the elastic and expansive properties of the foot and the angle of the pastern joint, enables the horse to absorb and dissipate a tremendous amount of shock when in motion. For example, an 1100-pound horse carrying 200 pounds weight and running a quarter-mile in 45 seconds with a stride of 20 feet, will absorb and dissipate nearly a ton a second on his lead foot. In so doing, he leaves only a shallow footprint in the dust.The Rearhand Assemblyat rest and catch weight at the end of flight in motion. Although the structure of the hind feet and legs is similar to that of the forelegs, less lameness and unsoundness occurs in the hind feet and legs because of their supporting less weight and doing less work. Proof of this is that the hind feet grow faster than the front feet.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 7June 1989 While the horse's center of gravity is located about six inchesto teach a horse a particular movement or response, the appropri ate behind the elbow, the center of motion, however, is locatedsignal must first be given and then followed immediately with approximately over the 15th vertebra. This bony structure is thesome stronger force or punishment which will result in the horse most upright member of the spinal column and on a mature horseresponding in the desired manner. Once the horse has learned the is about 10 inches back of the center of gravity. The horse inlesson, the punishment must be stopped and not used again except motion goes with these two centers in their relative positions. Theas a necessary reminder. Reversing the sequence of signal and position of the center of gravity, however, can be altered by thepunishment will only confuse the horse. rider shifting his weight from side to side or front to rear. TheHorses are born with a certain amount of intelligence which horse himself can even shift the center of gravity by raising,must be developed by training and good habits. What a horse lowering or extending his head. In contrast, the center of motionknows he must be taught by man and, depending on training, this appears to be rather fixed. A rider's weight, positioned as nearly ascan either be good or bad. possible over the center of motion, offers the greatest stability andThe horse may shy at unfamiliar objects. He may also shy at interferes with motion the least. Weight too far back lessens thefamiliar objects not in their usual place. Regardless, the hor se must horse's propelling power.never be punished in such situations or due to his power of object he sees. With his attention focused on the unfamiliar objectThe Power of AssociationIn the struggle to survive through the ages, the horse has learned to avoid or escape situations in which he might get hurt. He has, therefore, developed a great power of association. This is the basis of horse training. To capitalize on the horse's power of association, signals or cues and punishment in training must be in proper sequence. For example, association he may develop the bad habit of shying at every strange the horse, if he can think at all, blames the object for the punishment. It is, therefore, better to let the horse study the object until he learns he will not get hurt and thereby gain confidence in the rider. This may be a rather new idea to many present-day horsemen but the fact was observed by Xenophon, the Grecian soldier and scholar about 350 B.C.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 8June 1989Since both conformation and action need to be includedCoarseness about the head indicates a coarse body, lacking in light horse evaluation, the basic conformation featuresquality. The ear should be medium size, attractively set and tending to affect action must be understood. The relationshipcarried at a 45 degree angle to the axis of the head. Large, of body parts to performance (form to function) will be herefull, prominent eyes of a clear deep color are desired. Small discussed with the body of the horse divided into four areas:blue eyes are considered weak. Small narrow, squinty eyes 1. Head and Neck, 2. Fore Quarters, 3. Body or Trunk, 4.are often correlated with coarseness in quality and a lazy, Rear Quarters.sluggish, disposition. of prime importance because the horse cannot force air intoHEAD AND NECKThe ideal head for each breed is described by the association publications. The descriptions all say the head should be broad in the forehead and between the eyes, short from the eyes to the nostrils and deep in the jaws. These words mean only that the head should be in proportion to the parts of the body of the horse. The proportion of the head tends to be an indication of body proportions. For example, a long narrow head indicates a long, shallow, narrow body. Large nostrils allow for a maximum air intake and are the lungs through the mouth as is possible in other species of animals. All breathing of air by the horse must be done through the nostrils. All horses, both long and short necked ones, have seven cervical vertebrae. The shape of the neck is due largely to the amount and shape of the muscular tissues. The neck should be long, lean, and attached high up on shoulders with prominent withers. The lower part of the neck should be attached above the point of the shoulders. The throat latch should be cleancut and free from thick, meaty or fatty tissue to facilitate movement of the head at the poll and allow easy breathing.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 9June 1989Length of neck plays an important part in length ofshoulders are usually associated with short, steep pasterns stride. Over the neck lie several layers of muscles, some ofgiving a hard, jolting ride because of decreased shock which control the movement of the scapula or shoulderabsorption. blade, the arm, and indirectly the forearm. The muscles thatA long sloping shoulder also forms a more desirable control leg movements terminate at the knee. Cannon,base for neck attachment giving a better balanced, more pastern and foot action is controlled by ligaments andattractive horse. tendons. Larger neck muscles allow more muscle contraction extending the arm further and raising the forearm higher. This results in a longer stride. Another set of muscles extend from the front of the neck to the shoulder blade. Longer muscles here allow more shoulder blade movement and thus a longer stride. A thick neck adds excess weight to the front end. This causes increased shock to the front legs because they ordinarily carry two-thirds of the body weight of the horse. A thick neck also decreases head movement giving slow, awkward turns.FORE QUARTERSThe withers should be prominent or high and well The back which must also be short and heavily muscled defined. They should extend rearward about one-quarter ofgets additional support from the rib cage. Often weak backs the distance from the fore to the rear flanks. This is notresult from weak loins. possible unless the shoulder is long and has about a 45 A short back and loin coupled with desirable shoulder degree slope. Such withers give the horse opportunity toand withers results in a long underline. However, a long have a long stride besides providing a good seat for theunderline does not insure a large body capacity unless it is saddle. combined with long, deep, well sprung ribs. This The shoulder should be long, flat and smooth, with a 45combination of short back and loin, long underline and long, degree slope. This allows for increased shoulder movementdeep, well sprung ribs insures ample capacity for breathing which determines the arm movement and affects the stride.and consuming feed. In a steep-shouldered horse the arm does not extend very far Length of underline also affects freedom of leg forward during movement. This decreases extension of themovement. A short underline can cause a horse to forge. forearm and gives a short stride. Accordingly the slope ofThis is striking the undersurface of the front foot with the the shoulder increases length of the muscles and allows fortoe of the rear foot. more contraction and greater range of movement of the front leg. The legs of the horse should be attached to the trunk to give the appearance of being on the four corners of the body. When viewed from the front, the cannons should descend from the center of the knees. Cannon bones should give the appearance of being flat when viewed from the side. This doesn't mean that the bones themselves are flat, but that splint bones and tendons and ligaments are set apart, well tied and give support at the posterior of the legs. The front feet should be large, symmetrical and set at the same angle as the pastern. The foot should be especially wide at the heel and have considerable height at the heel as long as it is in keeping with the desired angle. When viewed from the side the best combination of length for the various parts of the front quarter calls for a long shoulder, short arm, long forearm and short cannon. This gives a longer, more elastic stride and more speed. A steep shoulder coupled with a long arm, short forearm and long cannon is the most undesirable shoulder and leg structure. This gives a severely shortened stride. SteepTRUNK OR BODYThe trunk or body of the horse should be deep and broad. The back should be short and the loin wide and smooth. The back and loin together make up the top line which must be strong to protect internal organs, bear the weight of the rider and transmit to the front end the propulsion generated by the hind legs. The loin has no bone structure for support, making it the weakest part of the top line. The loin is a bridge between the rib cage and the hips. In order for the loin to perform its function of transmitting power from the rear to front end, it must be short and heavily muscled.REAR QUARTERS
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 10June 1989The croup or rump should be long, wide and level. This2) Horses with low, rounding withers or thick withers often is the area from the loin to the tail head. Although the slopehang low-headed in the bridle and handle front legs of the croup differs with light horse breeds, a level croup hasclumsily. They often forge. longer muscles that enable a horse to take long strides and3) Length and slope of shoulders tends to correspond to maintain speed for great distance. A more sloping croup setslength and slope of pasterns. Properly sloped shoulders and the rear legs further under the horse so he may make apasterns (45 degrees) are related to a springy stride. Length quicker start with the more powerful stride. Regardless ofof shoulders and pasterns is related to the length of stride. breed or slope to the croup, it should be long so the croup4) Long forearms and gaskins are related to length of stride. muscles can make maximum contraction. All muscles in the5) Horses standing straight on front feet are more apt to croup and thigh must be strong to supply the power from the show straight stride and true action. rear quarters to propel the horse.6) Short, straight shoulders give a short, straight stride with Adequate gaskin muscling is desired. The outer gaskinconcussion. muscles help to pull the leg forward and enable propulsion,7) If the front legs are set far out on the corners of the body, giving the horse a long, powerful stride.a rolling, laboring action in front will result. This condition The powerful gaskin muscling also gives strength to theoften goes with thick withers and straight shoulders. legs in turning and pivoting.8) When points of the hocks turn slightly inward with points The rear quarter is comparable to the forequarter in thatof the toes slightly outward and the rear cannons parallel, a long croup, short thigh, long gaskin and short cannon givessuch a position of the rear legs is related to collected, rather the best stride.than spraddled, action behind. 9) When points of the hocks turn outward, often a defect inActionA long, straight, free elastic stride and coordinated, collected action is desirable. Excess lateral movement of the feet and legs reduces efficiency. Action is affected by the set of the feet and legs as well as by the anatomical characteristics already mentioned. Fairly close hock action with the hind legs working beneath the body is essential.EXAMPLES OF ANATOMICAL FEATURES RELATING FORM TO ACTION1) A thick neck and filled throat latch gives a lack of flexion of the head and slow, awkward turns. action called limber hocks or rotating hocks occurs. 10) A calf-kneed position of the front legs gives a pounding gait and hard concussion of feet at completion of the stride. 11) A pigeon toed horse will paddle or wing out when he travels. 12) A splay-footed or toe-wide horse will dish or wing in when he moves. 13) A straight stilty angle of pasterns will give a stilty action and may give cocked ankles or other unsoundnesses such as sidebones.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 11June 1989Soundness in the horse is of extreme importance, sinceto put weight on the affected limb, even in the standing his efficiency in performance is dependent upon his abilityposition. When moving, the lame horse is forced to carry to move.most of his weight on the sound limbs, hence the "nodding" Any abnormal deviation in the structure or function ofof the head when the sound limb strikes the ground. When a horse constitutes an unsoundness. All unsoundnesses dothe lameness is on the left fore leg, the head will nod as the not have the same degree of severity. Some unsoundnessesright foot is planted on the ground but will jerk up as the left can be treated successfully, others can not.or lame leg touches the ground. Lameness in both front legs An example of a blemish is an unsightly scar or ropeis indicated by a stiff, stilted action and short stride. The burn. A blemish does not interfere with the service ability ofhead is carried higher than usual without nodding. the horse.The exact location of lameness is often difficult to Any time a horse is lame, we can suspect and etermine. Many common unsoundnesses of the legs may be unsoundness. Lameness is any irregularity in gait whichdetected by carefully comparing the opposite leg. Swelling results from moving with pain or difficulty. Lameness mayand implantation can be observed by handling the leg. be detected while the horse is in a standing position,Most unsoundnesses of the legs and feet are caused by however, it is most noticeable at the walk or trot. If lamenessinjury, or excess stress and strain. Horses with faulty is severe, the horse will refuseconformation are always subject to unsoundness. Many times it is possible to detect an unsoundness by being familiar with correct conformation. Concussion lameness is associated with straight backs and pasterns, for example.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 12June 1989COMMON UNSOUNDNESSES AND BLEMISHESThe following unsoundnesses and blemishes are identified: U-unsoundness, B-blemish.Head1) cataract (U) cloudy or opaque appearance of the eye. 2) defective eyes (U) impaired vision or blindness. 3) poll evil (U) inflamed swelling of poll between ears. 4) roman nose faulty conformation. 5) parrot mouth (U) lower jaw is shorter than upper jaw. 6) undershot jaw (U) upper jaw is shorter than lower jaw.Neck1) ewe-neck faulty conformation.Withers and Shoulders1) fistula of withers (U or B) inflamed swelling of withers. 2) sweeny (U) atrophy or decrease in size of a single muscle or group of muscles, usually found in shoulder or hip.Front Le g s1) shoe boil or capped elbow (B) soft, flabby swelling at the point of elbow. 2) knee sprung or buck knee over on the knees. Faulty conformation. 3) calf-kneed back at the knees. Faulty conformation. 4) splint (B) capsule enlargement usually found inside upper part of front cannon. 5) wind puff (U) puffy swellings occurring either side of tendons above fetlock or knee. 6) bowed tendons (U) enlarged, stretched flexor tendons behind the cannon bones. 7) ringbone (U) bony growth on either or both sides of pastern. 8) sidebone (U) bony growth above and toward the rear quarter of hoofhead. 9) quittor (U) fistula of the hoofhead. 10) quarter or sand crack (B) vertical split in the wall of the hoof. 11) navicular disease (U) inflammation of small navicular bone usually inside front foot. 12) founder (U) turning up of hoof and rough, deep rings in hoof wall caused by over feeding, severe concussion or disease and abnormal management. 13) contracted feet (B) abnormal contraction of heel. 14) thrush (B) disease of the frog. FOUNDERED HOOF A SIDEBONE SPLINTS
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 13June 1989CONTRACTED TENDONS, COCKED ANKLE OR KNUCKLING CAPPED HOCKBody1) heaves (U) difficult breathing, lung damage. 2) roaring (U) difficult breathing due to obstruction usually in larynx. 3) rupture (U) protrusion of internal organs through the wall (hernia) of the body. Umbilical or scrotal areas most common. 4) sway back faulty conformation. 5) hipdown (U) fracture of prominence of hip and falling away.Rear Limbs1) stifled (U) displaced patella of stifle joint. 2) stringhalt (U) nervous disorder characterized by excessive jerking of the hind leg. 3) thoroughpin (U) puffy swelling which appears on upper part of hock and in front of the large tendon. 4) capped hock (B or U) enlargement on point of hock. Depends on stage of development. 5) bog spavin (U) meaty, soft swelling occurring on inner front part of hock. 6) bone spavin or jack spavin (U) bony growth usually found on inside lower point of hock. 7) curb (U) hard swelling on back surface of rear cannon about four inches below point of hock. 8) cocked ankle (U) usually in hind feet, horse stands bent forward, due to contracted tendons. 9) blood spavin (B) swelling of vein usually below seat of bog spavin.NOTES
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 14June 1989How old is your horse, mister? To such a 4-H1) Number and anatomy of teeth. question, the owner might answer full mouthed, smooth mouthed, he still has corner cups or I don't know as he isn'ta) The foal of either sex has 12 molars or grinders and registered. Such answers tend to confuse the youngster of12 incisors or front teeth for a total of 24 teeth. the motor age, nor can he readily find these answers toob) The mature male horse has 24 molars or grinders easily until he questions the grandfather age group.and 12 incisors or biters plus 4 canine teeth or tushes General features of horses which indicate advancedfor a total of 40 teeth. ages are grey hairs around the eyes and muzzle, deepc) However, the 4 canine teeth located in the depressions above the eyes, slender and hardened muzzlesinterdental space between the incisors and molars erupt and loose heavy lips with a longer grin than youngeronly in the gelding or s tallion. These canine teeth in the horses. But, these features are not accurate enough tomare are underdeveloped and seldom erupt above the estimate ages on younger horses. Since the horse is mostsurface of the gums thus giving the mare a tooth count useful to us from 3 to 15 years of age, we need moreof 36. accurate methods for age determination during this period.d) There are 6 incisors in each upper and lower jaw. The teeth of horses under 12 years old can be mostThere are 2 central incisors at the midline, 2 lateral closely identified with their approximate age. In general, weincisors and 2 corner incisors in each jaw. The corners must examine the incisor teeth for most accurate results. Ofbeing closest to the interdental space. course, the registered horse has a recorded birth date, bute) Anatomy of teeth. By studying the longitudinal many horses are not so fortunate. However, this technique issection of incisor teeth we can see how the tooth wears not foolproof as prolonged droughts, short grazing on sandyas age progresses. soils, cribbers, parrot mouths etc. all tend to make the horse appear different than his actual age. For instance, a horse at2) Examining teeth. 7 years of age grazing in sandy country over a prolonged period might appear to be 8 or 9 by his teeth.Approach the horse gently from the left side and The technique of horse age determination is not new norex amine the teeth by parting the lips with the thumb and especially scientific as it has been passed down for manyforefinger leaving the jaws closed. In examining groups of generations. The basics for determining the age of horses byhorses of mixed ownership ask the holder to part the lips. their teeth are rather simple and is not an art only to beThe angle of bit and size and color of teeth are noted first. guarded by the horse trader or veterinarian. Age can best beFor the next examination grab the tongue with the right estimated by examining the wear and slant of the incisorhand and grab the lower lip with the left hand and the mouth teeth.will open for clear examination of the cups, wear etc.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 15June 19893) General tooth eruption and development by ages. The 2) 2-year-old. All milk teeth in wear. temporary or milk teeth of the young horse are smallish and b) Second period (2 to 5 years). white with a distinct neck. The permanent teeth are much 1) 2 years. Temporary centrals loosen and larger, stronger and have a darker color with distinct cups on permanent centrals erupt. Age d etermination is the younger horse. *Inserts from The Sound Horse, Mich. most accurate from 2-5 years. Shedding of milk Ext. Bull 330. teeth and eruption of permanents may not occur a) First period (birth to 2 years). 2) 3 to 4 years. Permanent laterals erupt. 1) 10 months. All milk teeth have erupted and in 3) 4 to 5 years. Permanent corners erupt. wear at 16-18 months. simultaneously and may overlap one another
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 16June 1989c) Third period (6 to 9 years) 2) 15 years. The dental stars are smaller but more 1) 6 years. Age from here on is estimated mainly distinct and more centrally located. by the size, shape and disappearance of cups until 3) 20-21 years. At this age teeth may become 10-12 years of age. Cups disappear at rather shorter, more triangular in shape on the wearing regular intervals beginning with the lower centrals surface, have a noticeable spacing between at 6 years. adjacent incisors and the dental stars may become 2) 8 years. Cups have disappeared in the lower larger and occupy a central position on the wearing centrals and laterals. surface. Also, at this age, the bite is very slanting. d) Fourth period (aged). It is well to note that horses in this age group may 1) 10-12 years. After 9 years the accuracy of age appear to have much younger mouths if they have determination becomes more difficult. At this age had excellent care with regard to lush grazing and the angle of the bite slants more outward than the grain feeding with accompanying good health perpendicular bite noticed in younger horses. By throughout their life. 12 years, the cups have disappeared in the upper incisors and the horse has a smooth mouth.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 17June 1989GLOSSARYAnatomy The science of the structure of the animal body Full mouth When the horse has a complete set of and the relation of its parts.permanent incisors. Angle of bite The outer angle at which the upper and Incisor Slender teeth in front used for biting grass, feed, lower incisors meet.etc. Canine teeth Teeth that appear in the interdental space on Interdental space The gum space between the incisor the male horse at 5 years of age. Sometimes referred to asteeth and molar teeth. tushes. Centrals The first centrally located upper and lowercentral and corner incisors. incisors. Corners The corner incisors or those located back andtooth. adjacent to the forward edge of the interdental space (third set of incisors). Cribbers A bad habit of some horses in which the animal grasps the manger or other object with the incisor teeth, arches the neck, makes peculiar movements with the head, and swallows quantities of air. Called also cribbiting and wind-sucking. Crown of tooth The top of a tooth protruding above the gum. Cups The hollow space on the wearing surface of the incisor. Dental star A star shaped or circle like structure near the center of the wearing surface of the permanent incisors. Laterals The second set of incisors located between the Longitudinal Lengthwise. Parallel to the long part of the Molars Rear teeth or grinding teeth of the horse generally not used to determine age. Neck of tooth The part of the tooth between the crown and root located at the surface of the gums. Parrot mouth The upper incisors overhang the lower incisors and do not properly meet and therefore cause uneven wear. Smooth mouth Refers to the smooth biting surface of the upper and lower incisors after the cups have disappeared at 12 years of age or older. Wear Refers to the amount of use or wear observed on the biting surface of the incisors.NOTES
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 18June 1989The birth of a foal is the end of a wondrous process. It starts with the merging of two tiny cells one from the female animal (mare), one from the male (stallion). With the joining of these cells, a new animal is conceived. The cell from the female is called an egg, or ovum. The cell from the male is a sperm. The egg and sperm are both sex cells, the very special cells that contain the genetic material an animal inherits from its parents. Two microscopic cells will completely determine the genetic makeup of the offspring. See the discussion of genes and chromosomes in the guide sheet entitled How Inheritance Works in Horses. The production of sex cells is a unique and interesting process. Each of the two sexes has special organs to produce sex cells and carry out the process of reproduction. These are called the reproductive organs. Much of the reproductive process is regulated by secretions from the body's mature gland, the pituitary. A knowledge of many specialized terms are essential for you to properly understand and discuss this reproductive process. Study This Specialized Glossary Before ProceedingSPECIALIZED GLOSSARYAccessory glands (ak-ses-o-ri). These glands are located along the urethra of the male. They produce fluids that nourish and preserve sperm. Birth canal The birth canal includes the cervix and the vagina of the female. They are the organs through which the unborn animal passes at birth. Cervix (sur viks). This is the narrow passage or doorway between the female's vagina and uterus. Corpus luteum (kor pus lu te-um). A solid mass that forms in the follicle after the egg has left. It produces a hormone which helps maintain pregnancy. It prevents other follicles from developing while the unborn animal is growing in the uterus. Epididymis (ep I-did I-mis). A mass of tubes connected to the testicle. Its main function is to store sperm. Estrogenic Hormones Hormones that stimulate the development and maintenance of feminine sexual characters. The principal estrogenic hormones are: a) estradiol; b) estrone; c) estriol. Estrus (es trus). The estrus period is commonly called heat. Fetus (fe tus). The unborn animal as it develops in the uterus. Follicle (fol I-k 1). A bubble-like structure on the ovary which contains an egg. Follicle stimulating hormone (FSH). Comes from the pituitary and causes follicle growth. Hormone (hor mon). A body-regulating chemical secreted by a gland into the blood stream. Infundibulum (in fun-dib u-lum). The funnel-like membrane that surrounds the ovary. It catches the egg when it is released by the ovary. Luteinizing hormone (LH). Comes from the pituitary and regulates corpus luteum in female and testosterone secretion in male. Nucleus (nu kle-us). The dense center of a cell. It contains the genetic material. Ovary (o va-ri). A female organ that produces eggs. There are two ovaries. Oviduct (o vi-dukt). The tube which carries the egg from the ovary to the uterus. Ovulation (o vu-la shun). The time when the follicle bursts and the egg is released. Ovum (o vum). Scientific name for egg. Placenta (pla-sen ta). The membrane by which the fetus is attached to the uterus. Nutrients from the mother pass into the placenta and then through the navel cord to the fetus. When the animal is born, the placenta is expelled. It is commonly called the afterbirth. Pituitary This gland located at the base of the brain secretes hormones which regulate the body. Progesterone A steroid hormone secreted by the hypertrophied cells of the corpus luteum. It inhibits the action of estrogens. It aids in the development of the uterus for implantation and effective nutrition of the embryo. Prolactin A hormone produced in the anterior pituitary gland. It initiates lactation or in the case of nursing mothers milk secretion is stimulated. Sex cells The egg and the sperm. They transmit genetic material from the parents to the offspring. Scrotum (skro tum). The sac-like pouch that suspends the testicles outside the male animal. Sperm Male sex cells produced in the testicles. Semen (se men). Sperm mixed with fluids from the accessory glands. Testicle (tes ti-k 1). A male gland which produces sperm. There are two testicles. Urethra (u-re thra). The tube through which both semen and urine pass through the penis of the male. Uterus (u ter-us). The muscular, spongy organ of the female where the unborn animal develops. It is commonly called the womb. Vagina (va-ji na). The canal which leads from the uterus to outside the female. Sperm is deposited there by the male, and the fetus passes through the vagina at birth. Vas deferens (vas def e-renz). The tube that carries sperm from the epididymis to the urethra in the male.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 19June 1989MALE REPRODUCTIVE ORGANSThe primary sex organ of the stallion is the testicle. (There are 2 testicles.) The testicles produce sperm in the mature individual and also produce a hormone called testosterone. Testosterone regulates and maintains the male reproductive tract in its functional state. Testosterone is also responsible for the masculine appearance and behavior of the stallion. Each testicle contains a mass of minute, coiled tubules. The inner walls or surface of these produce the sperm. The numerous thousands of minute tubules merge into a series of larger ducts which pass out of the testicle to a larger, coiled tube located adjacent to the testicle. This tube, the epididymis, is the place where sperm are stored while they mature. Sperm formation in the male is a fairly continuous process. The testicles and epididymides are located in the scrotum which regulates the temperature of these structures. The scrotal temperature is several degrees cooler than that of the body cavity which is necessary for the normal development of sperm. From the epididymis, the sperm move through a tube, the vas deferens, into the urethra. The urethra is the tube that carries urine from the bladder through the penis. The urethra also carries sperm from the junction with the vas deferens to the end of the penis. Along the urethra are the accessory glands. Their names are the prostate, the seminal vesicles and cowpers gland. They produce fluids that nourish and preserve the sperm. During mating, the accessory glands discharge their fluids into the urethra. This washes the sperm forward through the penis. The combined fluid and sperm is called semen. Puberty, or the capacity to produce sex cells, occurs in the stallion at the age of approximately one year. This is not a period of mature breeding capacity. Two-year-old stallions may be used for limited breeding service. Breeding use of the stallion should be deferred until after the age of two. Ask your veterinarian or an experienced horseman to explain care and management of the mature stallion to you.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 20June 1989 canal) and into the world. The lining of the uterus is softFEMALE REPRODUCTIVE ORGANSThe mare's reproductive organs are quite different from the stallion's. The female produces the ova or eggs, receives the sperm from the male, and provides a place for the unborn animal to develop. The primary sex organ of the mare is the ovary. Each of the two ovaries is usually 2 to 3 inches long and somewhat bean-shaped. The other portion of the female reproductive tract is known as the duct system. It consists of the oviducts, the uterus, the cervix, and the vagina. The various parts of the duct system are connected together and attached internally to the upper body wall by a series of ligaments. The ovaries produce the eggs. Each egg is contained in a bubble on an ovary. This bubble is called a follicle. There are hundreds of follicles on each ovary. At the same time by a process not completely understood, one or more follicles begin to grow while the others remain small. The follicle grows until it is about an inch in diameter. It is filled with a fluid. The egg is suspended in the fluid. Near the time of mating, a hormone causes the follicle to burst. The fluid gushes out of the follicle, carrying the egg with it. The egg is then trapped in a very thin membrane that surrounds the ovary. Shaped like a funnel, this membrane is called the infundibulum. The infundibulum narrows into a tube called the oviduct. The oviduct carries the egg to the uterus, or womb. The largest of the female reproductive organs, the uterus is where the unborn young (the fetus) will develop. The uterus has a thick wall with heavy layers of muscles. At birth, these muscles will contract with great pressure to force the new animal through the cervix and vagina (birth and spongy, containing a vast network of blood vessels. This network of blood vessels provides a bed for the fertilized egg to settle into and develop.THE ESTROUS CYCLE AND FERTILIZATIONThe estrous cycle of the mare may be divided into phases, i.e., diestrus (quiet period); proestrus (preparation); estrus (heat period). The average length of the estrous cycle for mares is 22 days but may vary from 17 to 30 days. Individual mares tend to retain their individual cycle characteristics with regard to length of cycle and length of estrous. The mare is called polyestrus because she cycles continuously throughout the breeding season in the absence of conception. The mare is called seasonally polyestrus because there is seasonal fluctuation of the estrous cycle with regard to length, intensity and regularity. Most mares that exhibit no outward signs of estrus during winter months are said to be anestrous (without estrus) during that time. The estrous cycle may be irregular in the early spring. The most easily recognized phase of the estrous cycle is estrus (heat period) or the period of male receptivity. It is caused by the relatively large amount of a hormone, estrogen secreted during this state of rapid and maximum follicle growth. The average length of estrus is 6 days but often varies from 2 to 11 days. Periods usually decrease in length as the summer progresses. Ask your veterinarian or an experienced horseman to explain the external signs of estrus and for instructions on management of your mare during the breeding season.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 21June 1989The period when a mare is out of estrus is generally called diestrus. This phase or stage usually varies from 10 to 18 days. The first part of diestrus involves corpus luteum development. In the absence of conception, the corpus luteum regresses within a few days and new follicle development once again takes place under the influence of a hormone (FSH) from the pituitary gland. The period of rapid follicle growth at the termination of diestrus is commonly referred to proestrus. Many mares are capable of first reproduction at 4 years of age. Regular annual foaling is conducive to total life-time production. In most cases it is advisable to have mares examined for reproductive status prior to breeding. Policies regarding general sanitation, safety, and medical aspects should be observed in all equine breeding programs. Fertilization is the process of the uniting of the sperm and the ova. The tubular or duct portion of the female reproductive tract undergoes rhythmic contractions during estrus and this activity is stimulated by mating at which time the sperm is deposited in the tract. This pulsating action plus the locomotion of the sperm in a fluid medium transport the sperm through the cervix and uterus into the oviducts. The sperm and the egg unite in the oviduct. Only one sperm fertilizes a single egg although several million sperm may be present in the reproductive tract of the female. Only one egg is usually present per conception in horses. Sometimes a mare will produce two eggs and if both are fertilized, twin embryos will start to develop. Identical twins result from a different situation. In this case a single egg divides into two independent cells or cell masses at a very early stage of development. Twin embryos are undesirable in horses because they are generally aborted prematurely. The egg produced by the mare is small in size although it is much larger than a sperm. The egg has a nucleus which contains the genetic material. The sperm has a much different shape than the egg which is basically round. The sperm has a head, a middle section and a tail. The physical movement of the latter structure gives the sperm cell its property of locomotion in a fluid medium. The genetic material of the sperm cell is contained in the head section. Upon fertilization, a sperm penetrates the outside membrane of the egg and the head section is drawn into contact and union with the nucleus of the egg; thus the genetic composition of the new individual is established. Fertilization is also the stimulus for the egg to divide and grow to form the new individual. The fertilized egg usually undergoes its initial cleavages or divisions in the oviduct. Meanwhile, it is transported to the uterus where development progresses.PREGNANCY AND BIRTHPregnancy is the time during which the fertilized egg develops in the uterus. This process is also known as gestation. For a period of about six weeks, the cell mass resulting from the fertilized egg grows as a free floating object in the uterus. During this time, the fetal membranes commence to form. Nourishment of the new individual during this early stage is provided for by uterine secretions. The hormone progesterone secreted by the corpus luteum assist in regulating the reproductive tract during pregnancy. At approximately 6 weeks of pregnancy, the placenta attaches to the wall of the uterus and then provides for the nourishment of the fetus. Nutrients and oxygen are carried from the mare to the fetus and waste products from the fetus are eliminated through the placenta. The navel cord connects the fetus to the placenta. The process of gestation in the mare requires about 340 days; however, it may vary from approximately 300 to more than 400 days following breeding. The fetus develops gradually although the most rapid period of growth takes place during the last 3 or 4 months of pregnancy. Successful pregnancy ends in birth or parturition. At the proper time due to hormone action, the strong muscles of the uterus contract forcing the new animal through the birth canal and into the world. Until, now, the young animal received nutrients and oxygen from its mother's blood stream. But at birth the navel cord is broken. The animal must live on its own. Apparently the breaking of the navel cord stimulates the animal to breathe. This solves the problem of oxygen. As for nutrients, the mother's body has been preparing them for many weeks. The hormones produced during pregnancy have stimulated the milk glands. By the time of birth, they are ready to provide milk. Later, the mare will expel the remainder of the fluids and placenta to the completion of parturition. The entire process may require several hours. Milk production and letdown is initiated by hormones secreted by the pituitary gland. The first milk or colostrum is seen just prior to or after parturition. Colostrum is very high in proteins and other nutrients which provide the foal with resistance to infections. It is very important to the new born foal that it receives the colostrum. The colostrum is exhausted and replaced gradually with normal milk by about two days after the initial nursing. There will always be reproductive problems among horses but interferences may be minimized by good management practices. An understanding of some of the basic principles of the processes of reproduction can aid horse breeders materially in dealing with difficulties likely to be encountered.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 22June 1989 Two tiny cells are the only links of inheritance an animal haslinked to the protein of the chromosome. Genes are too small to be with its parents. A sperm cell from the sire and an egg cell from theseen with a microscope. But other research methods tell us they are dam unite and grow into the new animal.there. We know, therefore, that any characteristics inherited fromGenes are the units of inheritance. Characteristics are passed the parents must come from these two cells. With good care andfrom parents to offspring through genes. Genes are the "brains" of good nutrition, the material in the sperm and egg will determinethe cell. They determine what the cell will be like. This, in turn, almost everything about the developing animal its size, its shape,determines what the body will be like. its color, even is intelligence.Since chromosomes come in pairs, so do genes. Two genes The study of how characteristics are passed from parents toexist side by side, each on one of the chromosomes in the pair. The offspring is the science of genetics. It's easy to see why genetics istotal number of genes on a chromosome is not known, but t hey are important to horse breeders. In trying to understand the mysteriesmany. And different chromosomes have different numbers of of inheritance, geneticists learn things which help to produce bettergenes. horses.The unique thing about genes and chromosomes is that they As an animal grows, cells divide and form two. Before theGENES AND CHROMOSOMESInside the cells of animals are certain complex chemical compounds. These substances are the carriers of inheritance. They are called genes and chromosomes. Chromosomes are long, thread-like structures made of complex protein. They can be seen with a microscope. In all body cells except the sperm and the egg, chromosomes exist in pairs. Each cell contains a certain number of chromosome pairs,Genes and chromosomes act somewhat differently when depending upon the animal. Man has 23 pairs of chromosomes insperm cells and egg cells are formed. In the testes of the male and each of his cells. Here are the number of chromosome pairs forin the ovaries of the female, cell division happens another way. farm animals.The chromosome pairs separate, one member of each pair Horses33Pigs19going to one new cell and the other member going to the other new Cattle30Sheep27cell. As these cells divide again, the single chromosomes form Goats30Chickens 6duplicates which go into each of the new cells. This makes the Strung along the chromosomes, somewhat like beads on asperm or the egg contain only a single chromosome of each string are genes. Genes consist of complex molecules. They areoriginal pair of chromosomes. This type of division is called chemicallymeiosis. are able to reproduce themselves. cell divides, each chromosome duplicates itself. When the cell divides one of the duplicates moves into each of the two new cells. So the two new cells have exactly the same kind and number of chromosomes. This type of cell division is called mitosis.CHROMOSOMES IN SEX CELLS
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 23June 1989 In horses, the sperm from the stallion and the egg from thesmall b represent the red gene. Since genes come in pairs, a horse mare each contain 33 single chromosomes instead of 33 pairs.could have two b lack genes (BB), one black and one red gene(Bb), Because of the way chromosomes separate at meiosis, millions ofor two red genes (bb). A black horse could have either BB or Bb different kinds of sex cells can be produced by one animal.genotype. (Genotype means genetic makeup.) A red horse would When fertilization occurs, the single chromosomes from thehave bb genotype. The gene for red (b) is recessive to the dominant sperm join the single chromosomes in the egg. Once again pairsgene for black (B). are formed. So the fertilized egg contains the same number ofConsider this problem: A red (chestnut) mare (bb) is bred to chromosome pairs as the cells of the parents.a truly black stallion (BB). What color will the foal be? This fertilized egg develops into a new individual, resemblingAs the genes and c hromosomes divide in the mare's ovaries, each parent in some ways, yet different from them both. Andthe bb genes separate. Each egg contains one b gene. Likewise, probably different from any other individual in the world, since theeach sperm from the stallion contains one B gene. slightest difference in gene make-up would make a difference inWhen the sperm and egg unite, two genes influencing coat the animal.color are again present. The genotype of the foal will be Bb. Since the B gene for black dominates the b gene for red, the foal will beDominant and Recessive GenesMost characteristics are determined by several pairs of genes. For this reason it is impossible to tell exactly what an unborn animal will look like. A few characteristics, however, are determined by only one pair of genes. Black and red coat color in horses is one example. By studying characteristics such as this, we can learn something about how inheritance works. One pair of genes causes the coat to be either black or red, depending on which particular combination of the two genes is present. There is one gene for black and a corresponding gene (allele) for red. The horse will be black if he has two black genes or if he has one black gene and one red gene. This is because the black gene is dominant. The horse will be red only if he has two red genes. Here's how the genes combine. Let the capital B represent the black gene. We use the capital because black is dominant. Let the black. His phenotype (outward appearance) will resemble the stallion. Both would be black. But their genotypes are different. The foal is Bb and the stallion is BB. What then would happen if a black stallion that had a Bb genotype were bred to a red (bb) mare? Two possible kinds of sperm would be produced by the Bb stallion. Half of the sperm would have the B gene and half would have the b gene. It would be a 50:50 chance whether the B sperm or the b sperm united with the b egg from the mare. The genotype of the foal would be either Bb or bb. Thus half the foals from such a mating would be black and half would be red. Suppose a Bb stallion were mated to a Bb mare. Both the mare and the stallion would be black, but both would carry a recessive gene (b) for red. Half the sperm would carry the B gene. Half the sperm would carry the b gene. The same would be true for the eggs.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 24June 1989 Chances are 25 percent that the foal would have the BBcarrying a y chromosome happens to fertilize the egg, the foal genotype, 50 percent that it would have the Bb genotype, and 25would be xy. It would be a stallion. percent that it would carry the bb genotype.The chances are 50:50 for the foal to be male or female. Theoretically, of 100 such matings were made, 75 of the foals would be black. Twenty-five would be red. Of the 75 black foals only 25 would be truly black (BB) and 50 would carry a recessive red gene. What would happen if a red (chestnut) stallion were bred to a red (chestnut) mare? In this case all the eggs and all the sperm would carry the b gene. All foals from such matings would be red. There are also several other pairs of genes that control other coat colors in horses. The many possible combinations of these genes cause the many different color patterns we see.INHERITANCE OF SEXWe can use a similar analysis to show how the sex of a foaldominant and recessive. We see this in certain kinds of flowers. is determined.When the red flowering plants pollinate a white flowering plant, In horses, there is one pair of chromosomes which does notthe flowers on the new plant are pink instead or red or white. In exactly match. One is called the x chromosome and the other, thehorses, the palomino color pattern is similar to this. y chromosome. Stallions have one x and one y chromosome. TheirFinally, many things besides the genetic make -up affect a sex genotype is xy. Mares have two x chromosomes. Theirhorse. He may have the genes for running fast, but unless he is fed genotype is xx. (The small letters x and y do not indicate that eitherproperly, w ell-trained, and protected from injuries he may never is dominant or recessive.)win a race. In reduction division in the stallion, half the sperm contain anA horse with genes for just average temperament that is x chromosome and half contain a y chromosome. In the mare allproperly cared for may have a better disposition than one with egg cells contain x chromosomes.good genes that is treated badly. If a sperm carrying an x chromosome fertilizes the egg, theMuch remains to be learned about inheritance in horses. The foal will have xx genotype. It would develop as a female. If apresent-day popularity of horses should provide the incentive for spermfurther scientific study in this field.COMPLICATIONSSo far we have seen how inheritance works in its simplest form. This basic system forms the pattern for all inheritance. Complications arise where characteristics are influenced by more than one pair of genes. Most of the important traits in horses, such as conformation, temperament, physical performance, size, muscularity, and longevity, are influenced by many genes. With 33 pairs of chromosomes and hundreds of genes involved, it is impossible to know a horses complete genotype. Furthermore, all gene pairs do not work as completely
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 25June 1989The digestive system of the horse is different from that Mastication (chewing) is the mechanical reduction of of the other farm animals. Although the horse has a singlefood into finely divided particles which provide a greater compartment stomach like man, the pig, and the dog, thesurface area for the action of digestive juices. Mastication horse can utilize roughages like the cow which is a ruminant.also mixes the food with saliva which moistens the food thus This is possible because the horse has a special type offacilitating chewing and swallowing. This is especially intestine. helpful with dry foods such as hays. Saliva is a secretion The digestive system is composed of the alimentaryfrom 3 sets of paired glands (parotid, submaxillary, and canal and its accessory organs. The alimentary canal is asublingual) and other small glands found in the mouth. hollow tube which extends from the mouth to the anus andWater makes up 99% of the horse's saliva with the other 1% has the following parts: mouth, pharynx, esophagus,composed of inorganic salts (ions), and proteins. There are stomach, small intestine, large intestine, and anus. Teeth,no enzymes in the s aliva of the horse. The secretion of saliva tongue, salivary glands, liver, and pancreas are the accessoryin the horse is s timulated by the scratching (mechanical organs. action) of food on the mucous membrane of the inner Digestion is the process of preparation of food forcheeks. It has been estimated that a horse will secrete about absorption from the alimentary canal into the blood stream10 gallons of saliva in 24 hours. Hay will absorb 4 times its and elimination of the unabsorbed residue from the body.weight of s aliva while oats will absorb about its own weight: The digestive process includes the combined effects of6 lbs. hay + saliva = 30 lbs.; 6 lbs. oats + saliva = 12 lbs. mechanical, secretory, chemical, and microbiological The horse is well equipped for chewing tough, coarse factors. The mechanical factors are chewing (mastication),feeds with a set of 40 upper and lower teeth in the male: 12 swallowing (deglutition), movements of stomach andincisors or front, 4 canines, and 24 premolars and molars or intestines, and elimination of residue (defecation). Thecheek teeth. Mares have 36 teeth since they usually do not digestive glands secrete digestive juices. Bacteria andhave canine teeth which in the male are located in the space possibly protozoa are the microbial influences.between the incisors and premolars. Jaw movement is Understanding the structure (anatomy) and functionvertical (up and down) and lateral (side to side). Because of (physiology) of the unusual digestive system of your horsethis, the upper jaw is wider than the lower; therefore, helps you appreciate proper feeding of your horse. mastication can occur on only one side of the mouth at a lower teeth and on the outside of the upper teeth because ofMOUTHThe mouth is the first part of the tract, and the first act of digestion is grasping of food (prehension) to convey it into the mouth. The horses upper lip is the main structure in grasping food because it is sensitive, strong, and mobile. In grazing the action of the lip places the grass between the front (incisor) teeth which cut the grass off. In manger feeding, the loose food is collected by the lip with the aid of the tongue. Water and milk are drawn into the mouth by suction caused by a negative pressure in the mouth created largely by the action of the tongue. time. The cheek teeth wear sharp edges on the inside of the the lateral movement. These sharp edges cause damage to the tongue and cheek resulting in the horse eating slowly and wasting feed. Floating the teeth will remove these sharp edges. An annual check-up will prevent this and other dental problems. The lower incisors serve another useful function the detection of age. (see section 4)
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 26June 1989The horse is a relatively slow eater and chews foodHydrochloric acid (HCl) activates pepsin and cooperates thoroughly requiring 15-20 minutes to eat a pound of haywith pepsin in the breakdown of protein. The rate of and 5-10 minutes to eat a pound of grain.secretion of gastric juices is a continuous process with the Deglutition (swallowing) is the complex act, involvingrate increasing when food is eaten. a number of muscles and nerves, of conveying food from theIn the horse's sto mach food has a tendency to arrange mouth through the pharynx and esophagus to the stomach.itself in layers. The first food passes into the bottom region first food to form layers. The partially digested food doesPHARYNXThe pharynx is a 6-inch muscular, funnel-shaped sac belonging to the digestive and respiratory tracts whose passages cross in this region. Food must move through the pharynx quickly so that it will not enter the larynx (windpipe) or be forced into the nasal passages. Once food and water enter the pharynx, it cannot return to the mouth due to the blocking action of the soft palate. Horses for this same reason cannot breathe through the mouth.ESOPHAGUSThe esophagus is a muscular tube about 50 to 60 inches in length which extends from the pharynx down the left side of the neck to the stomach. Solid and semisolid food moves down the esophagus by wave-like contractions (peristalsis), while liquids are squirted down. These movements can be seen by observing a horse eating and drinking. Choke can occur in horses when food, especially dry grain, and other materials become lodged in the esophagus. Food and water will be observed returning through the nostrils. Peristalsis is a one-way action in the horse from the pharynx to the stomach; because of this, it is very difficult for the horse to vomit. The act of vomiting usually results in the rupture of the stomach or pneumonia from the vomited material beingSMALL INTESTINEforced into the larynx then to the lungs.STOMACHThe opening of the esophagus into the stomach, the cardia, is closed by a powerful involuntary ring-like muscle (sphincter). This also reduces the occurrence of vomiting since it is very difficult for material to pass from the stomach back into the esophagus. The horse has the smallest stomach compared with other farm animals. With only a capacity of 8 to 17 quarts, the horse should be fed portions of the daily ration 2 or 3 times daily rather than one large feeding. Several types of glands and specialized cells are found in the stomach walls. Gastric juice and mucous secretions are produced by these specialized glands and cells. Gastric juice contains hydrochloric acid (HCl) and two enzymes, pepsin and gastric lipase. Pepsin is the enzyme which helps digest proteins. Gastric lipase helps digest fats into constituent fatty acids and glycerol; however, fat digestion is mainly by pancreatic lipase in the small intestine. of the stomach with subsequent food lying on or around the not leave the stomach until it has reached two-thirds of its capacity. Excess food consumed beyond the capacity of the stomach along with partially digested food pass on into the intestine. The emptying of the stomach is a continuous process during digestion. It requires a 24 hour fast to completely empty a horse's stomach. Stomach movement due to muscular contraction mixes the food with gastric juices and passes the ingesta into the duodenum. When to water a horse has always been an important question. It has long been recommended never to water a horse during or immediately following eating because the water will wash food out of the stomach. This is not true. Drinking during or following a meal has no harmful effect on digestion since most of the water passes directly from the esophageal opening to the intestine opening which are located quite close together due to the U-shaped form of the stomach. Horses are prone to digestive disorders originating in the stomach. Feeding ground grains which are easily packed into a doughy mass, sudden changes in feeding, failure to reduce the grain ration during idle periods, and ingestion of excessive amounts of water are a few causes of stomach disorders. The small intestine is 70 feet in length and 3 to 4 inches in diameter; it extends from the stomach to the large intestine; it has three parts the duodenum, jejunum, and ileum. The capacity of the small intestine is 48 quarts. The material leaving the stomach and entering the small intestine is known as chyme, and it is a fluid or semi-fluid. Two main types of factors influencing digestion in the small intestine are movements of the intestinal wall and secretions from the pancreas (pancreatic juice), the liver (bile), and the intestinal glands (intestinal juice). The pancreatic juice is produced by the pancreas gland and contains several enzymes. Trypsin (activated trypsinogen) converts proteins and partly hydrolyzed proteins into peptides and amino acids. Pancreatic lipase hydrolyzes fats to fatty acids and glycerol, and pancreatic amylase which breaks down starch to maltose. Bile, a secretion from the liver, activates pancreatic lipase, assists in fat emulsification, and aids in absorption of fatty acids. The bile duct and pancreatic duct empty into the 3 to 4 feet long duodenum about 5 to 6 inch from the pylorus, the stomach opening into the intestine. In
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 27June 1989other farm animals, bile is temporarily stored in a B vitamins are definitely synthesized by the bacteria of gallbladder. The horse does not have a gallbladder; there isthe large intestine; however, in certain situations the a direct secretion of bile into the small intestine from theabsorption of most of them may not be adequate to meet the liver. need of the horse. On normal diets, B vitamin deficiency Simple tubular glands are found throughout the smalldoes not occur in the horse so adequate quantities of B and large intestine which secrete the sugar digestingvitamins are available either (1) in the feed (diet) or (2) by enzymes maltase, sucrase, and lactase. Each of thesebacterial synthesis. enzymes attacks the individual sugar with the name similar to its own (maltose, sucrose, and lactose). The enzyme breaks the sugar into glucose which can be absorbed. These simple tubular glands also secrete a lipase similar to pancreatic lipase. Absorption of many nutrients (Amino acids, sugars, fatty acids, minerals, and vitamins) occurs in the small intestine which is well equipped with small projections called villi. Villi increase the surface area which enhances absorption. Intestinal movements mix the ingesta with the digestive secretions, enhance absorption, move the material through the intestines, expel the residues, and assist in the flow of blood and lymph through the vessels of the intestinal wall. The great length of the small intestine leads to many problems such as twisted or telescoped intestine.LARGE INTESTINEMaterial which is not or cannot be digested in the small intestine passes into the large intestine which is divided into the cecum, large colon, small colon, rectum, and terminates at the anus. The important digestive action of the cecum and colon is due to the presence of bacteria and possibly protozoa (one celled animals) which (1) digest cellulose, the fibrous part of roughages, and other carbohydrates such as starch and sugars to produce energy yielding volatile fatty acids; (2) synthesize B-vitamins; and (3) synthesize amino acids. Absorption of volatile fatty acids apparently occurs in the colon. CECUM The cecum, blind gut, lies between the small intestine and large colon. Its average length is 4 feet with a capacity of 28 to 32 quarts. It extends into the right flank. The presence of food in the stomach causes an emptying of the cecum into the large colon. Because of the microorganism digestive action in the cecum, it is a functional appendix. LARGE COLON. The large colon with a diameter of 8 to 10 inches is 10 to 12 feet long and has a capacity of 80 quarts. The large colon extends from the cecum to the small colon where it terminates in a funnel shaped restriction. Because it is usually expanded with food, impactions may occur. Impactions occur also in the cecum and small colon. SMALL COLON. The small colon extends from the large colon to the rectum. It is from 10 to 12 feet in length with a diameter of 3 to 4 inches. Water is reabsorbed from the contents of the small colon and the characteristic balls of feces are formed. Feces is the waste matter of digestion and contains water, indigestible and undigested food residues, cells sloughed off of the intestinal wall, and remains of digestive secretions. RECTUM The rectum extends 1 foot in length from the small colon to the terminal part of the digestive tract, the anus. A horse normally voids 33 to 50 lbs. of feces per day. Vigorous horses defecate 5 to 12 times daily.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 28June 1989You probably feed your 4-H horse a supplement. You After digestion, the energy nutrients are carried by the know that the supplement will make your colt grow fasterblood to the cells of the body. In reactions very much like and be healthier. The horse will be in better shape than ifburning, they are used by the cells for energy. Energy or fuel you just let him graze. is required to power the movements of muscles walking, a You know this because you know something aboutbeating heart, breathing, blinking eyes and contractions of animal nutrition. Animals need many different kinds ofthe digestive system. At the same time, heat is produced to nutrients. Different animals need different kinds andmaintain body warmth. amounts of nutrients. This is where the science of animal The main energy nutrient is carbohydrate. There are nutrition comes in. Part of the animal nutritionist's job is tomany carbohydrates. Even the relatively simple ones are find out what nutrients animals need. complex compounds. All carbohydrates are made up of In feeding experiments, different feed ingredients arecarbon, hydrogen and oxygen. Carbon is the key to tried. In the laboratory, feeds are analyzed. Nutritionistscarbohydrates. This element can behave in several different search for the best combination of feeds for the kind ofways. As a result, there are thousands of possible horse being fed. For mares nursing foals, the feed must helpcombinations of carbon, hydrogen and oxygen. produce milk. For a pregnant mare, the feed is designed to Sugars and starches are carbohydrates. They are help produce a healthy foal. For a young horse, feed isrelatively simple. Cellulose is one of the more complex designed for growth and development as well ascarbohydrates. maintenance and energy. The sugars and starch are easy to digest. They have a After experiments are conducted, they are checked andhigh feeding value because very little of them pass rechecked. Then the results are used to makethrough the body undigested. Grains such as corn and oats recommendations to horse owners. This means good rationscontain much sugar and starch. for a minimum cost to horse owners. It also assures you that Cellulose is chemically a carbohydrate. It makes up the your horse is fed in a way to meet the needs of his body infiber in plants. Grass has much cellulose. Cellulose is hard the type of work that he is doing. to digest. For most animals it has a low feeding value; however, ruminants (cattle and sheep) can digest largeKIND OF NUTRIENTSThere are many different chemicals in feeds. Animals need some of them in large amounts others are needed only in tiny amounts. Some have not been discovered or named yet. These feed constituents are divided into five main types of nutrients. Each type has a different job in the animal's body. The five types are (1) energy nutrients (carbohydrates and fats), (2) proteins, (3) vitamins, (4) minerals, and (5) water. None of these is more important than the others. All are essential. But with the exception of water, the energy nutrients usually make up the greatest bulk of feed. Energy nutrients are the body's fuel. In fact, they are even chemically similar to fuels we use gasoline, oil and coal. amounts of cellulose with the aid of bacteria in the rumen. The caecum or large intestine of the horse functions similar to the rumen in cattle and sheep. Another group of energy nutrients is the fats and oils. Fats and oils are chemically alike. Their main difference is that fats are solid at body temperature; oils are liquid. Both are usually called fats. Like carbohydrates, fats are made up of carbon, hydrogen and oxygen. They are also used to provide energy for movement and heat. Fats contain a higher percentage of carbon and hydrogen atoms than carbohydrates do. Thus, the energy in fats is more concentrated. Fat has 2.25 times more energy per gram than carbohydrate.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 29June 1989THE PROTEINSWhile carbohydrates and fats supply energy, proteins supply the material from which body tissue is made. They are the bricks and mortar from which bodies are built. Proteins are highly complex. In addition to carbon, hydrogen and oxygen, they contain nitrogen. Some proteins also contain sulfur. A few contain phosphorus or iron. Like carbon, nitrogen can be combined with other chemical elements in different ways. The various combinations result in many different proteins. Each protein is made up of several nitrogen compounds called amino acids. These amino acids are the building blocks from which proteins are made. The chemical arrangement of the amino acids determine the quality of the protein. During digestion, proteins are broken down into amino acids. These are absorbed from the intestine into the blood stream and carried to all parts of the body. Then they are recombined to form body tissue. Proteins that are eaten eventually become muscle, internal organs, bone and blood. Skin, hair, hooves, and many other parts of the body are also made of protein. If an excess of protein is fed, the nitrogen portion of the protein can be separated from the rest of the nutrient and be discarded in the urine. The remaining materials can then be converted into energy by the animal. TWO PROTEINS ARE NOT ALWAYS ALIKE IF MADE OF THE SAME AMINO ACIDS! AMINO ACIDS123 PROTEIN #1PROTEIN #4 123321 PROTEIN #2PROTEIN #5 132312 PROTEIN #3PROTEIN #6 213231THE VITAMINSAlthough animals need large amounts of both energy and proteins, other nutrients are just as vital, but are needed in much smaller amounts. The vitamins are such a group. For a long time, people noticed that certain diseases were caused by the lack of certain foods. Then modern science began analyzing the foods. They were found to contain small amounts of certain complex chemicals. Other foods did not contain them. These nutrients were called vitamins, or vital amines. They are essential to normal body functioning. The vitamins are not chemically alike. Each one also has a different job in the body. Still, they are all classed together under the term vitamins. This is because they are all organic compounds. (They contain carbon). Also, all of them are needed only in very small amounts. Vitamin A is responsible for the health of the eye and the tissue of nasal passages, lungs and digestive system. Vitamin D is responsible for the strength and proper development of bones and the mineral balance in the blood. Other vitamins have just as important functions. Some animals require only certain vitamins in their feed, whereas others can manufacture some of their own. Feeds are a good source of certain vitamins. Carotene in green grass is a good source of vitamin A. Sunshine and suncured hay are good sources of vitamin D.THE MINERALSLike vitamins, minerals are usually needed only in small amounts. Unlike vitamins, they are inorganic they do not contain carbon. Iron, copper, phosphorus, calcium, and magnesium are examples of minerals.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 30June 1989Minerals are important in the chemical reactions of thenitrogen in a feed can be determined. Multiplying this body. Without them, many life processes could not takeamount by 6.25 (16 percent nitrogen divided into 100=6.25) place. Without iron in the blood, for instance, oxygen couldgives the amount of crude protein in a feed. It is called crude not be carried to the body's cells. For animals such as horsesprotein because it includes all nitrogen compounds. There that are very active, the oxygen carrying capacity of themay be some nitrogen compounds in the feed which are not blood is a very vital factor in their daily life. A race horsetrue proteins. uses tremendous quantities of oxygen during a race.Another test is for the amount of fat in a feed. Since fat Without calcium and phosphorus proper bone and toothdissolves in ether, a sample of the feed is heated in ether for formation would not take place. These are examples of theseveral hours. Then the feed is removed, and the ether is need for minerals.evaporated. The residue that is left is the fat, or ether extract. is because fiber is hard to digest. Therefore, feeds with aWATER AS A NUTRIENTThe last item on our list of nutrients is so common that we seldom think of it as a nutrient. But water is the largest single part of nearly all living things. The body of a colt is three-fourths water, while an adult is approximately 50 percent water. Water performs many tasks in the body. It makes up most of the blood, which carries nutrients to the cells and carries waste products away. Water is necessary in most of the body's chemical reactions. In addition, water is the body's built-in cooling system. It regulates body heat. It acts as a lubricant. Life on earth would not be possible without water. An animal can live longer without food than without water.FINDING OUT WHAT'S IN FEEDSResearch has provided the information that is available about the different kinds of nutrients. The scientist has developed methods by which the amount of each nutrient in a feed can be accurately determined. Knowing the nutrient content of a feed is very important to livestock raisers. Water is one of the nutrients that is fairly easy to determine. Simply take a sample of a feed and weigh it. Then heat the feed sample slightly above the boiling point of water. Hold it at this temperature until the feed stops losing weight. Then weigh the feed. This weight is subtracted from the weight before heating. The difference between the two weights represents the amount of water driven off by the heat. To find the percentage of water, divide the dry weight by the original weight. Another fairly simple analysis is to find out how much mineral is in the feed. Recall that minerals are inorganic chemicals. As such they will not burn. When feed is completely burned, a whitish-gray ash is left. If the weight of this ash is divided by the original weight of the feed before burning, the percent mineral, or ash, is obtained. The chemical analysis gets more complicated when you are determining how much protein is in a feed. Recall that protein is made up of carbon, hydrogen and oxygen plus nitrogen. Scientists have learned that protein is about 16 percent nitrogen. Using certain chemical tests, the amount of It is important to know the fiber content of feeds. This high fiber content are less nutritious. To find the fiber content, some of the feed is dissolved in a weak acid or alkali. Fiber (very complex carbohydrates) will not dissolve; it is left over. Any material that the weak acids or alkali will not dissolve is considered to be indigestible by animals. Keep in mind that the cells in the lining of the stomach secrete a weak solution of hydrochloric acid. If the percentage of water, minerals, fat, fiber and protein are added together, the total will be something less than 100 percent. This difference is referred to as the nitrogen-free extract. This extract includes the more soluble carbohydrates, sugars, starch and some cellulose. All of these are readily digested in the digestive tract. When the amounts of different nutrients in a feed are known, the quality or feeding value of the feed can be easily determined. By adding the digestible organic nutrients (protein, nitrogen-free extract and fat x 2.25), we can tell the energy value of a feed TDN total digestible nutrients is the term used.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 31June 1989A great variety of feeds may be used satisfactorily for horses. In different parts of the world, horses are fed elephant grass, bamboo leaves, dried fish, turnips, beets, leaves of limes and grapevines, and lawn clippings. As a general rule, we should choose feeds that are suitable and readily available at the most economical cost. Therefore, we may say that the ABC's of choosing feeds for horses are based on knowledge of nutrient content and function of the horse, combined with experience of the horse owner. In this lesson we learn about the content of energy, proteins, minerals, vitamins, and fiber or bulk contained in some of our most important feeds for horses. Also, we learn about correction factors to consider, such as quality, suitability, availability, cost, and convenience. We gain experience by applying these ABC's to provide economical, satisfactory rations when we have a thorough understanding of the digestive system of the horse, the nutrients and their importance, and balancing rations for the horse.TYPES OF FEEDSWe can conveniently classify feeds into three main types: (1) roughages, (2) concentrates, and (3) mixed feeds. Roughages include pasture forages, hays, silages, and byproduct feeds that contain a high percentage of fiber. Concentrates are the energy-rich grains and molasses, the proteinand energy-rich supplements and byproduct feeds, vitamin supplements, and mineral supplements. Mixed feeds may be either high or low in energy, protein, or fiber; or they may provide complete balanced rations.ROUGHAGESWild horses live on roughage today as their ancestors did 55 million years ago when they were five-toed animals the size of a fox. Roughages are still important for active horses and may serve as the only feed for idle horses. Proper use of good quality roughages reduces the quantity of expensive concentrates needed and provides a plentiful supply of vitamins and minerals. There are three main forms of roughages: (1) dry roughages, (2) silages, and (3) pastures. Dry roughages include hay, straw, and artificially dehydrated forages, which contain about 90 per cent of dry matter. Silages are formed from green forages such as grass, alfalfa, sorghum, and corn preserved in a silo at dry matter contents of 20 to 50 percent. Green, growing pastures provide forage that has a high water content and only 20 to 30 percent of dry matter. There are two basic types of roughages: (1) grasses, and (2) legumes. The grasses are generally higher in fiber and dry matter than legumes. The legumes are generally higher in proteins, energy, vitamins, and minerals. Soil fertility, soil type, and climate influence the productivity and nutrient content of the various grasses and legumes. But the most important factor affecting the nutrient composition of grasses and legumes is stage of maturity As a plant grows older, it becomes less leafy, more stemmy, more fibrous, and less digestible. Timothy hay cut before bloom has about 160 percent more digestible protein and 35 percent more TDN than mature timothy. Mineral and vitamin levels are also higher in immature grasses and legumes, whether these roughages are in the form of pastures, silage, or hay.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 32June 1989and also causes a loss of these nutrients from fermentation.DRY ROUGHAGESIn general, the best hay for horses is a good quality grass legume mixed hay. A good quality pure legume or pure grass hay is satisfactory if it is fed properly. Grass hays such as timothy, oat, brome, bermuda, wheatgrass, native western mountain, etc. of equal quality have similar nutrient values. Prairie hay is much lower in protein than most other grass hays. The legume hays (alfalfa, soybean, peanut, lespedeza, and clovers) are generally higher in protein, energy, calcium, and phosphorus than grass hays. Mixtures of grasses and legumes are intermediate in nutrient content. Because the calcium level in legumes is about six times higher than the phosphorus level, a supplemental source of phosphorus might be needed to balance the Ca:P ratio in a ration high in legumes. If we learn to identify the grasses and legumes by their leaves and blossoms, we can do a more intelligent job of buying. Also the head of grasses and the bud or bloom of legumes can tell us the state of maturity at which the hay was cut. Horses refuse and waste more late cut hay, which is already low in nutrient content. Leafiness of hay is an important guide to feeding value because most of the nutrients are carried in the leaves. For hay to grade U.S. 1 or U.S. 2, 25-40 percent of its weight must be leaves. Leafiness is influenced by kind and species of forages, stage of maturity when cut, weather conditions while growing and while curing, and curing procedures. Leaves are shattered and lost when hay is raked or baled too dry. Color of hay is another indication of quality and nutrient content. Good hay is a bright leafy green. Overly mature hay is pale, yellow, or brown. Hay that was rained on when it was nearly cured may be faded in color because of additional drying time and exposure to sunlight and air. ThisG ood quality silages are a suitable replacement for up exposure destroys the carotene or vitamin A value. Heavyto half of the hay or pasture allowance. Remember that rain on nearly dry hay leaches carbohydrates or energy valueabout three pounds of silage are equivalent to one pound of from the hayhay Hay that is baled before it is dry enough will lose nutrients through fermentation or heating in the bale, which sometimes starts a fire from spontaneous combustion. Even if it does not start a fire, heat of fermentation is energy value lost and produces a dull, dark hay that is usually dusty with moldiness inside the bale. Such hay is unacceptable for horses; therefore open and examine several bales of a prospective purchase if there is any question about its quality. Tight, clumpy, misshapen bales are subject to suspicion. Odor of hay will vary according to species of grasses and legumes but should always be aromatic and pleasant. Lack of odor indicates over-maturity, bleaching, leaching, or old hay which probably has lost most of its vitamin A value. A stale, musty, unpleasant odor indicates that excessive fermentation has occurred. Dust is objectionable in any feed for horses. It not only reduces the palatability of the feed, but also can cause heaves and other respiratory trouble. Good timothy tends to be most dust-free of the hays. Pure legume hays tend to be more dusty than grass or mixed hays. Dustiness can be reduced by sprinkling the hay or other feed with water or water and molasses just before it is fed. Dehydrated roughages such as alfalfa leaf meal or pellets are made by processing lush-growing, highly nutritious forage through a heated dryer called a dehydrator. These dehydrated meals or pellets are usually rich in vitamin A value, B vitamins, and high quality proteins. They are used mostly as vitamin and protein supplements, but their high fiber content classes them as roughages.SILAGES
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 33June 1989because of the difference in dry matter content. However,is used in most mixed feeds and also as ear corn, shelled spoiled, moldy, or frozen silages cause digestive upsets incorn, or cracked corn. Cracking improves its digestibility, horses. Silage that contains dead rats, birds, etc. can causebut finely ground corn is more apt to cause colic unless it is fatal botulism poisoning in horses.mixed with a bulky feed. higher in fiber and much more bulky, and about 15 percentPASTURESPastures can reduce feed costs and provide plenty of vitamins and good quality proteins. They are important for mares and foals, and night pastures especially are good for pleasure horses. However, an exercise lot with a few blades of grass is not a pasture. Such a lot or an overgrazed pasture of short forage can be a serious source of internal parasite infestation. Horses should be rotated to fresh pasture every two weeks if possible. This will reduce internal parasite infestation and also increase the productivity of pastures, particularly if the pastures are small. Understocked, overgrown, coarse, and unpalatable pastures are sometimes clipped to freshen them up during the growing season. Pasture forages are quite laxative in early spring. Legumes are more laxative than grasses. Therefore, laxative feeds such as linseed oil meal or wheat bran should be removed from the ration when horses first go on pasture, and their daily time on pasture should be short at first.CONCENTRATESCorn, oats, barley, and milo (sorghum grain) are the most important energy-rich grains. They contain about 70 to 80 percent of TDN (total digestible nutrients) including 7 to 10 percent of digestible protein. Wheat bran, rice bran, wheat middlings, rye middlings, and rice polish are byproduct feeds from the grain milling industry. The brans are somewhat laxative and bulky and usually contain about 65 percent of TDN of which 8.5 to 14 percent is digestible protein. Soybean oil meal, cottonseed oil meal, peanut oil meal, and linseed oil meal are called protein supplements. They have about 75 to 80 percent TDN and 30 to 46 percent digestible protein. Mineral concentrates include: salt, or sodium chloride (NaCl); iodized salt (NaCl plus iodine); ground limestone, which supplies calcium (Ca); steamed bonemeal and dicalcium phosphate for calcium and phosphorus; and others. All of the vitamins can be obtained in concentrated form, singly and in various combinations. Corn is similar to the other grains in nutrient content but is the richest in TDN and the lowest in protein, fiber, calcium, and phosphorus. Corn is the most readily available and most economical grain in most sections of the country. It can be used to full advantage if its deficiencies are offset by (1) good quality legume or grass-legume hay or pasture, (2) a suitable grain milling byproduct feed, or (3) a protein supplement. It Oats are somewhat higher in protein than corn, much lower in energy. Nutrient content of oats varies considerably according to proportion of fibrous hull to nutritious grain. Rolled or crimped oats is more digestible than whole oats. Oats with a grass hay such as timothy may be inadequate; some grass-legume roughage along with some corn or barley will assure a more complete ration. Oats are usually the most expensive feed grain in terms of cost per unit of nutrient. However it is the safest and easiest to feed and goes well with other grains that tend to cause colic. Barley rolled or ground medium fine is worth about 10 percent more per pound than crushed oats. Since barley may cause colic if fed alone, it should be mixed with at least 15 percent bran or 25 percent oats. Milo (grain sorghum), like barley, should be crushed or ground and fed with bran or oats. It then has TDN and protein values intermediate between barley and corn. Molasses is a concentrated appetizer and dust settler. It is sticky, sweet, and smells good. It contains 54 percent of TDN, very little minerals, no fiber, and no digestible protein. Unit cost of TDN is usually as high or higher than the cost of the same amount of energy as grain. However, either cane or sugar beet molasses is nearly always included at levels of 5 to 15 percent in commercially mixed rations. Protein Supplements A protein-rich supplement is needed when: (1) the roughage being fed is of poor quality, or (2) the pregnant or lactating mare or young stock requires extra protein to balance the ration. High protein feeds that are commonly used for horses are: soybean oil meal, linseed oil meal, cottonseed oil meal, and peanut oil meal. Protein quantity and quality in soybean and peanut oil meals is higher than in linseed and cottonseed oil meals. Linseed oil meal is the lowest of these in protein and usually is not the most economical source of protein, but it is used for its laxative quality and to improve the luster and bloom of hair coats. Although these protein supplements are high in energy value also, feeding excessive amounts is useless, expensive, and causes digestive upsets. Byproduct feeds Certain byproducts from the milling industry are useful, economical horse feeds. Wheat bran and rice bran are highly palatable and slightly laxative, therefore they improve rations of grass hay and corn, barley, or milo. The brans are especially good sources of two B vitamins, thiamine and niacin. and supply fair amounts of protein and energy. Wheat middlings, rye middlings, and rice polish are lower in fiber and higher in energy than the brans; they may cause colic and other digestive upsets if they comprise more than 25 percent of the concentrate ration.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 34June 1989Table 1. Daily Nutrient Requirements of Horses Based on mature weight of 1000 to 1200 lbsDaily Feed PerDigestibleTotal DigestibleCalciumPhosphorusVitamin A Horse lbs.Protein lbs.Nutrients lbs.gramsgramsIntl. Units*400 pound weanin g (a g e about 6 months) 11 to 121.0 to 1.28.0 to 9.033.021.012,000 600 to 700 pound y earlin g 13 to 141.6 to 1.89.0 to 10.033.021.016,000 800 to 1000 pound 2 y ear old 15 to 161.3 to 1.510.0 to 11.417.017.025,000 1000 lb. mature idle horse (less than 1 hour ridin g dail y )16 to 170.6 to 0.86.0 to 8.112.012.0 8,000 1000 lb. horse li g ht work 1 to 3 hours ridin g dail y 16 to 170.8 to 1.08.0 to 11.024.021.018,000 1000 lb. horse medium work 3 to 5 hours ridin g dail y 19 to 200.9 to 1.111.0 to 14.024.021.018,000 1000 lb. horse hard work more than 5 hours ridin g dail y 22 to 231.2 to 1.414.0 to 17.024.021.018,000 1000 lb. breedin g stallion (moderate breedin g ) 20 to 221.6 to 1.713.0 to 15.060.040.032,000 1000 lb. bred mare li g ht work 18 to 201.1 to 1.310.0 to 12.024.024.024,000 1000 lb. lactatin g mare 28 to 301.9 to 2.118.0 to 20.040.040.040,000* Horses can use carotene to produce Vitamin A at the rate of 400 International Units of Vitamin A from 1 mg. of caroteneYour 4-H horse project offers an opportunity for you to 5) Multiply each figure in Section 1 by the pounds fed learn how to balance a ration. To accomplish this, you must daily (Section 2, column 1). Record the results in the be accurate in your addition, multiplication, division and appropriate columns of Section 2 on your work sheet. subtraction. You will be working with percentages, so be 6) Add the columns in Section 2. This gives the total sure and watch decimal placings. amount of each nutrient in your horse ration. You can use Nutrient Requirement Tables in two ways: 7) Check these totals against the Daily Nutrient (1) to check the ration being fed to see if it is balanced, and Requirements listed in Section 3 of your work sheet. If (2) to formulate an adequate ration for your horse. the requirement is more than the totals in your ration, Follow this procedure in checking through the example you will know that your ration is inadequate. Your next ration and in working out a ration for your horse on the step is to find a feed ingredient that is a good source of blank sheet. the deficient nutrient and either substitute this new 1) Determine the age, weight and type of work your feedstuff for one you are now using or add this new horse is doing. ingredient to your horse ration. After doing this, you 2) Fill in Section 3 of the enclosed work sheet from should refigure your totals to be sure other nutrients are Table 1, Daily Nutrient Requirements of Horses. not out of balance. Excesses of some nutrients can 3) List available feeds in Section 1 of your work sheet, interfere with use of others in addition to being a waste giving attention to each column. If you have actual of feed and money. For example, excess calcium can analysis on your feeds, use these. If not, take average prevent complete utilization of phosphorus in a ration. analysis from Table 2. 4) Weigh the amount of each feedstuff being fed daily. If a mixed feed is being used, you can either find out the amount of each feed ingredient that is in the mixture or use analysis of the mixture from the feed tag.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 35June 1989Table 2. Average Nutrient Content of FeedsFeed DigestibleTotalCalcium gramsPhosphorusCarotene mg. Protein %Digestibleper lb.grams per lb.per lb. Nutrients % ConcentratesRolled Oats 11.0 75.0 0.41 1.95 0.0 Corn No. 2 7.8 85.0 0.09 1.22 1.3 Rolled Milo 9.3 83.0 0.14 1.22 0.0 Rolled Barley 10.6 80.0 0.41 2.13 0.0 Wheat Bran 12.3 65.0 0.63 5.90 1.2 Wheat 14.2 75.0 0.22 1.86 1.4 Soybean Oil 42.0 78.0 1.27 2.77 0.0 Linseed Meal 30.0 75.0 1.60 3.20 0.0 Molasses 0.0 53.7 3.35 0.36 0.0RoughagesTimothy 4.6 51.0 1.04 0.91 10.0 Oat Hay (green)5.0 47.3 0.95 0.86 14.0 Wheat Hay 3.8 46.7 0.95 0.86 14.0 Smooth Brome 6.1 46.3 1.63 1.18 16.7 Crested 5.4 51.0 1.00 0.60 2.2 Kentucky Blue 6.5 51.0 1.00 0.94 20.0 Prairie Hay 3.7 43.1 2.80 0.56 14.0 Clover-Timothy5.5 46.2 4.00 0.86 6.1 Alfalfa 12.4 50.3 6.60 1.06 16.8 Ladino Clover13.0 44.8 6.20 1.60 73.1 Red Clover 7.6 44.3 6.13 0.86 16.7 Mixed Grass 5.1 53.8 2.65 0.80 9.0 Reed Canary 4.8 45.1 1.63 0.82 7.0 Oat Straw 0.7 44.7 0.86 0.45 0.0 Convert Carotene to International Units of Vitamin A by multiplying by 400
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 36June 1989
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 37June 1989BALANCING HORSE RATIONS WORK SHEETAnimal____________________ Weight___________ Age______________ Work Classification_________________________Section 1 Composition of Feeds FeedProtein grams pergrams perInternational Units DigestibleCalciumPhosphorusVitamin A %lb.lb.per lb. of feed T.D.N. % Section 2Quantity of Nutrients in Feeds Being Used FeedLbs. fedProtein Digestible lbs. T.D.N.CalciumPhosphorusVitamin A lbs.gm.gm.I.U. Total Section 3Daily Nutrient Requirements (Based on air-dry feed containing 90 percent dry matter) Size andT.D.N.CalciumPhosphorusVitamin A Use of Horselbs.gm.gm.I.U. Lbs. fedProtein Digestible lbs. Section 4 Balancing Ration and Meeting Requirements Total from Section 2 Ration deficiency Supplement Balanced ration
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 38June 1989There are good reasons why you should be concerneddrafts. Most respiratory troubles develop from keeping with maintaining the proper health of your horses or ponies.horses in tight barns which are too warm and humid. First, you have a responsibility to all animals entrusted3) Carry out a planned immunization and parasite control to your care to protect them from injury, sickness and pain.program. Secondly, any time your horse is ill it will prevent youThe scientific basis for this recommendation is: from using him.Contagious diseases are caused by microorganisms, Thirdly, if your horse needs treatment, it will usuallymostly bacteria and viruses. However, your horses can cost you time and money.develop defenses against many microorganisms. These If we take the horse industry as a whole, we find thatdefenses are the antibodies in the blood. thousands of dollars are lost each year because horse ownersBy v accinating your horses against specific diseases did not follow the prescribed practices of good breeding,they will build up their antibody defenses against possible feeding, management, and disease prevention. This is sad,invasion by microorganisms. indeed, since the knowledge and materials necessary toThe secret of successful immunization is to have a prevent most of these losses are readily available.methodical plan, developed in consultation with your Animal scientists have discovered many practices whichv eterinarian and then to carry it out before disease strikes. horse owners find beneficial in the maintenance of healthyVaccination after your horses have been exposed to disease horses. There are many fine drugs, vaccines, disinfectantswill seldom give them enough time to build up their and other products manufactured today that can be useddefen ses to a large enough degree. You might sustain serious successfully to help keep horses healthy. Fortunately thelosses in such a case. people in veterinary medicine are ready and willing to helpHorses are often inoculated against tetanus since this in the wise use of these materials and in helping you to setorganism is usually present in horse stables. up a sound health program for your horses.Internal parasites can cause stunting, illness and even There are many preventive measures which are goodd eath if not controlled. They are particularly harmful to foals common sense ideas with scientific principles behind them.and colts up to two years of age. Periodic examination of Some of the more important ones are listed below.fecal samples from your young horses by your veterinarian 1) Feed your horses a nutritionally balanced ration, inwill give you information on the extent of the problem. sufficient quantities in the correct manner.The most scientific way to prevent disease and The scientific basis for this recommendation is:parasitism in your horses is to plan a total immunization and A horse's well-being depends largely on its nutrition. Ifparasite control program with your veterinarian. You must the level of nutrition is high, the body defenses againsthave your horses vaccinated at the right time, with the right diseases will be stronger. This also applies to the problemsvaccine and by the best method to be sure they will build up of internal parasites. Unsoundnesses of the feet and legs arean immunity. You must also treat for parasites at the proper sometimes traced to deficient rations. The same is true oftime and with the proper material in the prescribed way to other abnormalities such as infertility and abortion. It issuccessfully protect your horses. possible to overfeed horses and by so doing create serious4) Get an accurate diagnosis of the disease problem from a problems. A horse may founder, become temporarilyveterinarian. infertile or aggravate respiratory problems from being over-The scientific basis for this recommendation is: fed. Some of these troubles are caused from feeding moldyCorrect diagnosis of illness or abnormal conditions in or dusty feed or from feeding or allowing access to coldyour horses is necessary before they can be treated water too soon after heavy work.intelligently. Improper treatment based merely on 2) Provide clean, healthful quarters for your horses.supposition can result in loss of time and money or even the The scientific basis for this recommendation is:animals involved. Disease organisms often grow and thrive in organicA diagnosis requires much specialized knowledge and waste. Flies and insects as well as vermin, which also harbormany procedures. V eterinarians have this knowledge and disease, thrive under filthy conditions. Removing the sourcealso the equipment necessary to make the study. If they lack (reservoir) of the disease organism lessens the chances ofin either facilities or knowledge in a special situation, they disease.can call on the state diagnostic laboratories and scientists for If your horse is kept in a clean environment, his bodyassistance. will not be constantly fighting to ward off disease.5) Keep your horses well exercised, groomed and feeling Therefore, he will make better use of his feed, will feelfit. better and perform better because of less stress from disease.The s cientific basis for this recommendation is: Horses do best when allowed plenty of freedom toIf your horses are confined and cannot exercise by exercise and plenty of clear fresh air, provided there are noth emselves they will lose muscle tone, they may become stiff
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 39June 1989or lame and their digestive systems will not function as Your local veterinarian is best qualified to help outline effectively. Horses in their natural state had the opportunitya disease control program. He is trained in his field and he for unlimited exercise in a clean, outdoor environment. Thisis acquainted with the major disease problems in your enabled them to keep fit which meant they were betterparticular area. equipped to ward off disease and unsoundnesses. By keeping in constant touch with your veterinarian he 6) Consult your veterinarian. Plan a disease prevention andknows the history of your horse or horses and will be in a parasite control program with him. better position to make an accurate and rapid diagnosis. The scientific basis for this recommendation is: Disease prevention will probably be most effective Preventing disease is more effective than treating yourwhen you and your veterinarian work together in all phases horses after they become sick. of the disease prevention program.NOTES
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 40June 1989An infectious disease is one caused by the presence inis received. These cases are known as acute or on an animal body of a living foreign organism, which byDuring the course of any disease many organisms its presence creates a disturbance leading to the developmentescape from the host. Sometimes they are eliminated with of symptoms.blood, or from an abscess. Sometimes they are passed out A contagious disease is one that may be transmittedwith droplets of moisture which accompany a cough or a from one animal to another by direct or indirect contact. Allsneeze as in respiratory infections. Sometimes the organisms contagious diseases are also infectious, but it does notare eliminated through fecal material or urine as in intestinal follow that all infectious diseases are contagious. Foror urinary infections. (The virus of rabies is eliminated example, tetanus, caused by organisms which live in the soilthr ough the salivary glands and usually enters the body of is infectious but not contagious since it is not transmittedthe new host through a bite or wound and is not normally directly from one animal to another.spread otherwise.) Some infectious diseases are highly contagious. SomeOccasionally an animal and the infected organism will are slightly contagious and a few are not contagious at all.reach the point where the organism is unable to cause How contagious a disease is depends upon how the diseaseserious damage to the host, yet the host is unable to organisms are eliminated from the body of the diseasedeliminate the organism. This situation may continue animal, their opportunity for reaching others and their abilitythro ughout the lifetime of the animal. Such animals are to produce disease in the new hosts.capable of shedding organisms causing disease in contact Disease-causing organisms vary greatly in their abilityanimals. We refer to these animals as carriers Carriers may to produce disease. When the ability to produce disease isnot show symptoms of disease but are a source of great great, the organisms are referred to as virulent .danger to others who lack the same amount of resistance. Animals also vary in their ability to resist or repelThe carrier is one of the great problems of control of many disease-producing organisms. An animal's ability to resist ainfectious diseases. Animals that are obviously diseased may particular organism is known as immunity The immunity ofbe recognized, but there is no simple way of recognizing an animal may vary from slight to absolute .carriers. Sometimes animals develop disease-resisting propertiesThere are many sources of infection for your animals. within their bloodstream. These properties repel theWe usually think of direct contact with the diseased invading organism. Sometimes these properties are strongindividual. enough to remain for the life of the animal (permanentDisease may also occur when inanimate objects carry immunity). Other times they pass in a few months or a yearinfection from one animal to another. This can occur in a (temporary immunity). Vaccination is a means of artificiallytrailer, a railroad stock car or trunk contaminated with the stimulating the immunity of the animal without giving itfecal material and not properly cleaned and disinfected. actual disease. To do this the virulence of organisms isContact with apparently healthy disease carriers is a lowered until it no longer possesses the ability to activelymajor hazard. These carriers may infect others directly or cause disease but can stimulate the development of immuneindirectly as readily as the obviously diseased animal. properties in the body of the host animal. These live but Infection from soil Certain organisms live in the soil attenuated organisms are known as a vaccine Other timesand are able to produce disease in animals if chance carries the organisms are completely killed and the products of theirthem to the ti ssues (example: tetanus). growth used to stimulate immunity. This preparation isDisease may be contr acted from food and water that has known as a bacterin .been contaminated by a diseased animal (example: Because disease-producing organisms reach a hostleptospirosis). animal does not always mean that the animal will developAir-borne infections occur when droplets of moisture disease. Sometimes the animal's resistance is high enough orare sn eezed or coughed into the air (example: strangles or the virulence low enough that the organisms are destroyedrespiratory infections). by the host. This process is continually going on asSome infections are carried by bloodsucking insects organisms capable of producing disease are constantly(example: Equine encephalitis or sleeping sickness). present. If something happens to lower the resistance of the Disease Prevention Most contagious diseases can be animal or to raise the virulence of the organism, then aprevented by: (1) avoiding contact with sick animals, (2) disease process can start. If the host and invading organismspreventing indirect contact by using clean trucks. Insist on reach a standoff, the infection makes little or no headwaynew grain sacks for purchased feed. Keep visitors from other but persists for a long time. This is known as a chronic stables with manure or dirty clothing from contacting your infection animal, his feed or water supply. Use private water pail at If the invading organisms rapidly overcome thefairs or shows, etc. (3) Raise your animal's resistance by resistance of the animal, then death usually ensues unlessgood feeding, sensible use and care and vaccination when rapid resistance to the organism is developed by the host orindicated. Normal use of the animal prevents completely suitable treatment isolated or
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 41June 1989100% protection from exposure. Therefore you should striveof providing their own w ater bucket at fairs or shows then to raise the resistance of your animal by keeping him wellmake the mistake of filling the bucket from a common nourished and in a good state of health. Do not allow antrough. animal to become too tired or to chill. Chilling might occurVaccination will raise an animal's resistance to many from riding for long distances in cold, windy, uncovereddiseases. Strangles (or distemper), tetanus (or lockjaw) are trucks or being tied in a cold rainstorm. Such stresses greatlyexamples. Your v eterinarian can advise you as to diseases lower an animals resistance to disease.common in your area that can be prevented by vaccination. Always provide clean drinking water, and when horsesGeneral information concerning common diseases of are gathered in large groups, water your horse from anhorses is presented in table 1. individual bucket, drawing the water directly from the tap,For add itional information of diseases of horses, contact not dipping it from the trough. Many people go to the bother your veterinarian. COMMON EQUINE DISEASESDisease Outstanding Symptoms Treatment or ControlEquine EncephalitisFever, impaired vision, irregular gait,Annual vaccination is recommended in areas (Sleeping Sickness)incoordination, yawning, grinding of teeth,where the disease is prevalent. No specific drowsiness, inability to swallow, inability to riseagent is available for treatment and treatment when down, paralysis and death.consists of supportive measures and good nursing. Consult your veterinarian. Strangles (Distemper)High temperature, increased respiration,Antiserum and bacterin are available. Provide depression, nasal discharge after 2nd or 3rd day,comp lete rest. Avoid stresses of cold, drafts, or swelling of lymph nodes which usually abcess.moisture. Fresh drinking water at all times. Encourage eating. Consult your veterinarian for systemic treatment and care of abcesses. Tetanus (Lockjaw)Follows infection of deep puncture wound,This disease requires professional treatment. incubation period from 1 week to several months.Mortality is high. Disease is widespread and it First symptoms stiffness and third eyelid mayis recommended that all animals receive draw over the eye when excited. Spasms occurprophylaxic vaccination. This is particularly after 24 hours, reflexes increased, animaldesirable in brood mares because of the added frightened or excited. Spasms of neck and backdanger of infection at foaling. muscles cause extension of the head and neck. Azoturia (MondayOccurs soon after being put to work, stiffness,Decrease grain feeding and allow exercise Morning Sickness)sweating, affected muscles, swollen, tense, maywhen animals are off work. Careful, slow assume sitting dog position.warm-up after rest. Animal stopped immediately after beginning of symptoms have a good chance to recover. Do not move the animal any distance. Blanket the animal to keep it warm and quiet. Call your veterinarian for systemic treatment. Laminitis (Founder)May be acute or chronic, follows feeding ofAcute case, apply cold pack to feet. Call excessive grain or lush pasture, fast work on hardveterinarian. Chronic founder, trim feet shoe roads, large amount of cold water while animal isto protect sole. Prognosis not good. hot, toxemias following pneumonia or metritis, acute case shows inflammation of sensitive laminae on one or more feet, feet warm, sensitive to touch, very lame, pain on standing, temperature to 106 sweating, chronic cases hoof becomes distorted, anterior hoof wall concave, wall becomes corrugated (rings parallel to hair line).
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 42June 1989Have you ever been aggravated by swarms of mosquitoes, irritated by ticks and chiggers, or agitated by fleas? These discomforts and many more are experienced by some horses for extended periods of time because of external parasites. A parasite is defined as a plant or animal living on, in, or with another living organism (its host) at whose expense it derives food and shelter. External parasites of horses usually bite (with the exception of certain flies) and/or suck blood for food, and use body temperature and the hair of the host for comfort and shelter. Foals and young growing horses are especially susceptible to all types of parasites, which may result in temporary or permanent lack of development. External parasites are a problem to many horses. They are often associated with improper nutrition, mild forms of disease, stress, and sometimes conditions of general neglect. External parasites are easier to eradicate or control than internal parasites, but response to treatment may be disappointing unless a total health program is practiced. The most common external parasites are (1) flies, (2) lice, (3) mites, (4) ticks, and (5) a fungus causing ringworm. Both ringworm and mange mites are communicable to man.FliesFlies are a constant source of annoyance to horses, making them restless and ill at ease. The house fly and face fly feed on skin, nasal and eye secretions, or debris, but do not bite. The tenaciousness of the feeding face fly makes its presence particularly annoying to horses. They are commonly found in the northern half of the United States. Horn flies, stable flies, and deer and horse flies are biting insects that suck blood. Since they show a preference, some horses are severely harassed by these pests. Biting flies can be vectors of serious diseases such as encephalomyelitis. Blow flies are common to large areas of the United States, and effect damage by laying eggs in wounds. One type hatches into maggots which feed on dead tissue, retarding healing and enlarging the wound. The other type hatches into screwworms, which feed on live tissue, causing severe damage and sometimes death. Both types are easily eradicated by cleaning the wound and applying a proper medicant.ControlFly control is best effected by removal of waste and decaying vegetable material. Manure should be stored in covered containers or spread thinly (for rapid drying) on fields not used by horses. Remove moist hay, straw, garbage. and grain frequently during warm weather. Use screens when practical.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 43June 1989Life Cycle TreatmentThe four stages of the life cycle are the egg, the larva, Successful treatment of flies varies from one part of the the pupa, the adult. House, stable, and horn flies commonlycountry to another and will be influenced by the degree of lay their eggs in manure or occasionally in decayingimmunity they have established for a specific product. For vegetation or any moist collection of spilled grain. Face fliesthis rea son a qualified person should be consulted for lay their eggs in fresh manure on pastures. Horse and deerrecommendation in a given area. Regardless of the area, flies deposit eggs in the mud of swamps, salt marshes, or onpesticides should be considered poisonous and should be vegetation near water. regarded with extreme caution. Read the directions carefully HORSE FLY and follow them closely. Do not permit sprays to contaminate feed or surfaces that horses will lick. Do not store them where they may accidentally get into feed. Baits are effective but poisonous and should be placed out of reach of horses because many contain enough sugar to induce their consumption. Strands or cords treated with insecticide and hung in stables are often effective. Daily sponging or spraying may be necessary to give protection from horse flies and face flies. For those insecticides commonly used and recommended for your area, contact your local county agent or veterinarian.LiceLice that infest horses are of both the biting and sucking kind. Long hair is conducive to maximum reproduction and spread of lice, thus they are often observed in poorly groomed and poorly housed horses, especially in early spring. Symptoms include rubbing, biting, general unthriftiness, and patches of skin denuded of hair.Life CycleThe adult lice attach their eggs to the hair, usually close to the skin (the so-called nits). Here they hatch in from 11 to 20 days. The young lice reach maturity and the female begins laying eggs when she is 11 to 12 days of age. Lice live their entire lives on the host, and can exist only about three days when off the host animal. STABLE FLYBITING LICE
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 44June 1989SUCKING LICEPreventionProper feeding. grooming, and clean stabling will do much to prevent louse infestations. Lice may be carried from one animal to another on harness, saddles, blankets, brushes, or curry combs moved directly from a lousy animal to one free from lice.TreatmentHorses may be dipped, sprayed, sponged, or dustedsources for information regarding the prevailing regulations thoroughly for lice control. The treatment should befor the kinds and use of insecticides. repeated in two to three weeks in order to destroy the lice hatching from eggs not destroyed by the first application. Contact your county agent or veterinarian for the recommended insecticides most commonly used in your area under prevailing regulations.MitesMites are microscopic creatures that cause horse mange. Positive identity is difficult because skin scrapings must be examined carefully under a microscope. Three genera exist: Sarcoptes Psoroptes, or Chorioptes Sarcoptic mites burrow under the skin scurf where they lay eggs and reproduce. Chorioptic type may cause foot mange resembling scratches, although all three may cause mange on any part of the body. Symptoms include irritation, itching, inflammation, loss of hair, crusty scab formation, and folding of the skin.Life CycleFemale mites lay from 10 to 25 eggs during the laying period, which lasts from 12 to 15 days. After this period the female dies in the burrow. Eggs hatch in 3 to 10 days into young mites. After passing through several molts, they reach maturity and are ready to begin egg laying again in from 10 to 12 days.TreatmentMange is difficult to eradicate in any species of animal. Experience indicates that infested animals should be retreated every 7 days in order to gain control. Dusts are not effective. Spraying or thorough wetting with a brushwashing technique is necessary to reach the well-hidden mites. Your county agent or veterinarian are your bestTicksTicks are a problem to horses in many parts of the country. Like other biting insects, they are vectors of some serious diseases. Piroplasmosis recently infected over one hundred horses in the southeastern part of the United States. In 1960, the red tick, carrier of African horse fever, was identified for the first time in this country, in zoo animals in Florida. TICKS MALE
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 45June 1989TICKS FEMALELife CycleThe four stages include the egg, the six-legged larva orbe carefully disposed of. Children are particularly prone to seed tick, the eight-legged nymph. and the adult. Transitionringworm infections. from one stage to the next occurs by molting. The number ofUnder the best manag ement conditions horses harbor generations produced annually varies from one every two orsome parasites. Their effect is not spectacular or may be more years up to four or five per year, depending on theunnoticed, but they decrease work efficiency and cause species. All ticks attach to the host and feed on blood.discomfort. Heavy infestations render horses useless and total health program should be effected.TreatmentIn areas where ticks are a serious problem, dipping entire animals must be resorted to. If only a few ticks are found, swab them with cotton dipped in alcohol or chloroform. Since ticks breathe by means of spiracles or MAN AND OTHER ANIMALS; PARTICULARLY holes found on the abdomen, this tends to anesthetize or suffocate them. Several insecticides are available. Follow the recommendations of your county agent or veterinarian regarding their use.Rin g wormRingworm is caused by various species of fungi, arranged in circles on the skin. If penetration is deep enough, severe itching results; and secondary infection may lead to abscesses. The lesions are usually covered with greyish crusts through which short hairs protrude.TreatmentIf only a few lesions are present, soften crusts with warm soap and water and remove, dry the area, and paint with tincture of iodine daily for one to two weeks. If lesions are extensive, contact your veterinarian, since there are many new fungicides more effective than iodine. When treating or handling infected horses, use rubber gloves and wash hands thoroughly after treatment. All scrapings should may cause death or permanent damage. For these reasons a PRECAUTIONS MOST INSECTICIDES ARE POISONOUS TO CONCENTRATES PRIOR TO DILUTION FOR APPLICATION. ALL PRECAUTIONS ON THE LABELS SHOULD BE FOLLOWED FOR THEIR USE AND STORAGE. READ THE LABEL CAREFULLY! AVOID CONTAMINATION OF FEED AND WATER WITH INSECTICIDES. RINGWORM OF THE HORSE DUE TOHORSE HAIR INFECTED BY T. EQUINUM TRICHOPHYTON EQUINUM ECTOTHRIX TYPE OF PARASITISM, X522
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 46June 1989According to Webster's Dictionary, a parasite is a plant8) Rotate pasture plots as frequently as possible to break the or animal living in, on, or with another living organism (itslife cycle of the parasites. host), at whose expense it obtains food and shelter. More9) Flies should be prevented from breeding by keeping than 150 different kinds of parasites have been found tosurroundings free from manure, wet straw, and bedding. infest horses. Almost all horses harbor some parasites.10) Grain should be kept in covered containers away from External types include lice, flies, ticks, mange, andflies, birds, and rodents, which may carry parasites from ringworm. The internal types, which we will deal with in thisfarm to farm. lesson, include strongyles or blood worms, ascarids, stomach worms, pinworms, and bots. Every horse owner should have his animal on a parasiteprevention and control program. In order to draw up such a program, it is important to know the life cycle of the various worms so that proper preventive and treatment procedures can be followed.Economic ImportanceThe effect of the presence of worm parasites are not usually spectacular. However, they do cause decreased workA regular program for worming horses should be efficiency, poor utilization of food, are one of the causes ofadopted in cooperation with your veterinarian. Horses colic, may be the cause of intermittent lameness, may causeshould be wormed in the fall after the first killing frost, and a chronic cough and bronchitis, and occasionally death dueagain in the spring before they go out to pasture. If to blood clot. Some adult worms produce toxins that destroystrongyles are a particular problem continuous low-level red blood cells, leading to an unthrifty anemic condition.feeding of phenothiazine should be considered. Immature worms migrating through body tissues open theIn some areas, worm control programs are organ ized on way for bacteria and fungi to enter, causing other seriousa community or county basis. Since some of these parasites diseases.are transmitted by insect vectors, area action tends to reduce the possibility of this type of transfer. Such projects shouldPrevention of parasitismInternal parasites gain entry to the animal body in the form of eggs, larvae, or adults. This may be largely prevented by various forms of management which break the life cycle of the parasite. Those worms already present will have to be killed by drugs, depending on the kind of parasitetheir habit to hover about the horse, and then quickly darting present. The following practices have been found to betoward the animal they glue individual eggs to the hair in a effective in reducing parasite numbers:matter of seconds. The female of the common bot usually 1) Do not feed hay or grain on the floor. This preventslays up to 500 eggs. Eggs are usually deposited on the hair contamination of feeds with manure, which may containof the for elegs. although they may be deposited on the mane, large numbers of parasite eggs or larvae.shoulders, belly, chin, and occasionally the flanks. 2) Do not allow horses to obtain water from barnyard pools or water holes on pasture, since manure drainage into these areas makes them a source of internal parasites. 3) Clean stalls and rebed as often as possible so that there will be less chance of internal parasites getting on feeds from fecal material. 4) If the stall floor is of earth, remove ten to twelve inches once or twice yearly and replace with clean soil. 5) Remove manure from premises daily and either spread on a field where horses will not graze for a year or where the field will be plowed and reseeded before horses have contact with it. 6) If manure must be left near the barn, keep in a covered pit where it can heat and thus kill parasite eggs and larvae. This will also prevent fly breeding. 7) Small, heavily used pastures tend to build up a heavy parasite load. Small exercise yards should not contain pasture grasses which encourage animals to eat contaminated material. It is best to have them gravelled.TreatmentTreatment is a necessary but small part of the total parasite control program. Major emphasis should be on prevention. Even though adult worms are eliminated from the animal, damage has already been done by larval migration through body tissue. All drugs used for worming are dangerous and must be used with extreme care. In most cases, it would be best to have your veterinarian perform this service. be considered with your veterinarian, your county agent or your 4-H club leader.Bot FliesThere are at least three species of horse bot flies. It is BOT FLY
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 47June 1989The horse tends to lick or bite itself where the eggs are attached, thus stimulating hatching, and the newly-hatched larvae are taken into the horse's mouth in this manner. Some larvae burrow into the tongue and migrate through the body tissues until they finally arrive in the stomach where they attach to the stomach wall. They arrive in the stomach in three to four weeks. They mature in the stomach in ten to eleven months, at which time they release their hold on the stomach wall and pass out with the animal's feces. Mature larvae burrow into the ground and change into pupa stage. In fifteen to seventeen days the mature bot fly emerges from the pupa case and mates to begin the cycle again.Stomach WormsThere are at least ten different types of stomach worm, four of which are known to cause lesions, resulting in an inflammation of the stomach wall. The larval forms of the larger stomach worms are thought to be responsible for a skin disease of horses called summer sores. The larger stomach worms are approximately an inch to an inch and a half in length. Adult worms in the horse's stomach lay eggs which are passed out with the manure and picked up by maggots (larval forms) of the house fly or small stable fly. The stomach worm eggs hatch in the head region of the adult fly where they had come to rest as the fly matured. Horses probably swallow infested flies accidentally, or larval worms may leave the flies while they are feeding on the moisture around the horse's lips. Once in the horse's mouth, they are readily swallowed and mature into adult worms in the horse's stomach to repeat the cycle.Ascarids (intestinal worms)Adult worms in the small intestines deposit eggs which pass out with the manure. During warm weather, embryos develop within the eggs and are infective in about two weeks. Embryonating eggs are swallowed by grazing horses, the embryos are liberated in the small intestine, penetrate the gut wall, and are taken by the blood stream to the heart and lungs. After about one week's period, the larvae escape from the lungs, migrate up the trachea to the throat region where they are once again swallowed and the worms develop to maturity in the small intestine. Adults are approximately nine to twelve inches in length. BOT LARVA
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 48June 1989Stron g yles (blood worms, palisade worms)The horse strongyles are a large group of approximately forty species infesting horses. Most of them are less than an inch in length and scarcely visible to the unaided eye. They are usually found firmly attached within the host, sucking blood. Female worms deposit large numbers of eggs which leave the horse with the manure. After the eggs hatch, the larvae molt twice before becoming infective. Infective larvae climb to the upper portions of pasture grasses and are usually swallowed by horses during grazing. Larvae migrate to various organs within the body, depending somewhat upon the species. Those that favor the walls of the arteries are responsible for certain types of lameness and even death due to embolism by restricting or blocking blood flow in the arteries.PinwormsPinworms are approximately two to three inch long white-appearing worms with long slender tails. They are frequently seen in the feces of infected animals. The worms mature in the large intestines, and females full of eggs proceed outward through the small colon and the rectum, sometimes crawling out of the anal opening. The irritation causes infested animals to rub themselves against posts and other objects. Adult worms in this manner are crushed, at times leaving the eggs glued to the anal region. Normally, however, the eggs develop in manure and are picked up during grazing or feeding by horses to repeat the cycle. The vigorous rubbing of the posterior parts results in the loss of hair and occasionally injury may result in secondary infection. Fourth stage larvae are also found attached to the mucosa of the colon and are voracious feeders.
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 49June 1989GLOSSARYAnemic (a n m k). Deficient in red corpuscles of the Larva (lr v). The immature, wormlike form into which blood; a state causing paleness, weakness, heart palpitation.certain insects hatch from the egg. Bronchitis (br n k t s). Inflammation of the bronchial Maggot (m g t). A soft-bodied, grublike, footless larva of tubes (Extensions of the windpipe).an insect, as of the housefly; applied especially to forms Colic (k l k). An acute abdominal pain; may be caused by a great variety of disorders. Molt (m lt). To cast off or shed the hair, feathers, horns, Embolism ( m b l zm). The lodgment of an abnormal or foreign particle, such as an air bubble or blood clot, in a tube Parasite (p r s t). A plant or animal living in, on, or with or canal of the circulatory system, which tube being tooanother living organism (its host), at whose expense it small to permit its passage.obtains food and shelter. Embryos ( m br z). Organisms in the early stages of Pupa (p b p). An intermediate, usually motionless, form development, as before hatching from the egg.assumed by metabolic insects after the larval stage, and Insect vector (v k tr). An insect which carries and transmits disease-causing microorganisms. Trachea (tr k ). The main tube of the respiratory living in decaying matter. outer layer of skin, etc., being replaced by new growth. maintained until the beginning of the adult stage; a chrysalis. system; the windpipe.NOTES
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 50June 1989Table of AuthorsSectionTitle Author University1Behavior and Nature of the Horse N. A. JacobsenMontana State University 2Functional Anatomy and Action Joe B. JohnsonWashington State University 3Unsoundness and Blemishes Morris HemstromUniversity of Idaho 4Determining the Age of a Horse by Its TeethR. B. Warren University of Nebraska 5Principles of Reproduction in Horses Walter Smith Kansas State University 6How Inheritance Works in Horses Bobby J. RankinNew Mexico State University 7The Digestive System of the Horse Frederick HarperRutgers The State University 8Feed Nutrients H. B. HedgepethMississippi State University T. W. WickershamIowa State University 9Feeds for Horses Edwin E. GoodwinUniversity of Maryland 10Balancing Rations for Horses R. D. Setzler Washington State University 11Health and Sanitation Principles Important inDonald J. BalchUniversity of Vermont Horse Care 12Disease Problems of Horses Roy Hostetler Washington State University 13External Parasites Affecting the Horse Melvin BradleyUniversity of Missouri 14Internal Parasites of Horses Douglas Stern Universty of Massachusetts
4-H Horsemanship Pro g ram: Unit 2 -Horse Science Pa g e 51June 1989NOTES
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, Christine Tay lor Waddill, Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June 30, 1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, ag e, sex, handicap or national origin. The information in this publication is available in alt ernat e f ormats. Sing le copies of extension publications (excluding 4-H and youth publications) are available free to Florida residents from county extension offices. Information on copies for out-of-state purchase is available from Publications Distribution Center, University of Florida, PO Box 110011, Gainesville, FL 32611-0011. Information about alternate formats is available from Educational Media and Services, University of Florida, PO Box 110810, Gainesville, FL 32611-0810. This information was published June 1989 as CO 201, which is superseded by 4HHSG01, Florida Cooperative Extension Service. 1 This document is 4HHS 1, which supersedes CO 201, one of a series of the 4-H Youth Development Program, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date first printed Au gust 1965 revised June 1989. Please visit the ebsite at http://edis.ifas.ufl.edu. 2.De bbie Glauer, member of 4-H Animal Science Design Team, Department of Family, Youth and Community Science, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.