Equine Husbandry

Equine Husbandry

Terminology and Physiologic Data

Box 6-1 lists common terminology used to describe the age and breeding status of horses. Box 6-2 lists normal physiologic data for horses.

Breeds of Horses

Common Draft Horse Breeds


The Brabant is also known as the Belgian Heavy Draft horse. Its principal breeding area began around Brabant, Belgium. The Brabant is a massive, powerful horse about 16.2hh (hands high) to 17hh. It is short backed and compact. It has very strong, short, sturdily built legs, with ample feathering. The head is small in proportion, square and plain, but the expression is intelligent. The breed is notable for its kind temperament (Fig. 6-3).


The traditional centers of breeding for the Shire horse are the English counties of Leicestershire, Staffordshire, and Derbyshire, and the Fen country of Lincolnshire. The Shire typically stands over 17hh tall. It is one of the biggest horses in the world and weighs more than a ton. Its neck is relatively long for a draft horse. It runs into deep oblique shoulders, which are wide enough to carry a collar. The legs are clean, hard, and muscular. The hocks should be broad and flat and set at the correct angle for optimum leverage. The hooves should be open; they should be wide across the coronet and have plenty of length in the pasterns. The lower legs carry heavy but straight and silky feathering. Black with white feathering is still the most popular coat color, but numerous gray teams are seen, and bay and brown are also acceptable (Fig. 6-6).

Common Light Horse Breeds

American Paint

Each Paint horse has a particular combination of white and any color of the equine spectrum: black, bay, brown, chestnut, dun, grullo, sorrel, palomino, buckskin, gray, or roan. Markings can be any shape or size and located virtually anywhere on the Paint’s body. Although Paints come in a variety of colors with different markings, there are only three specific coat patterns: overo, tobiano, and tovero. Horses of this breed can be registered in the American Paint Horse Association (APHA). The APHA is the second largest breed association in the United States (Figs. 6-8 to 6-10).


The name Appaloosa comes from the breed’s point of origin in the Palouse region covering parts of Washington and Idaho. The Appaloosas are known for their distinctive color, intelligence, and even temperament. Four identifiable characteristics are coat pattern, mottled skin, white sclera, and striped hooves. In order to receive regular registration, a horse must have a recognizable coat pattern or mottled skin and one other characteristic. The seven basic coat patterns are blanket, blanket with spots, roan, roan blanket, roan blanket with spots, spots, and solid. Appaloosas that meet these requirements can be registered with the Appaloosa Horse Club (ApHC) (Fig. 6-12).

Cleveland Bay

The Cleveland Bay (CB) horse is one of the oldest native breeds of England originating in the northern regions. Cleveland Bays are classified as a light draught breed, not “warm blood,” although it is thought that there is no draught blood in the purebreds. They are primarily known for their solid bay color, large ears, blue/black hooves, clean legs, and their calm, kind personality. The Cleveland Bay Horse Society (CBHS) in the United Kingdom maintains a closed stud book for purebreds. An upgrading program exists, but entries are rare. Until 2005, purebreds in the main studbook were limited to a solid bay color, but a very small star was allowed. Current rules accept purebreds with “excessive” white, slight roaning, and chestnuts (which remain very rare), but they are listed as mismarked on registration papers. Fewer than 1000 purebreds exist worldwide, with about 180 in North America. Cleveland Bay crosses, often referred as “partbreds” or “sport horses,” are sometimes misidentified as purebreds. This is an indication of the strong influence the breed has on other breeds when crossed. Separate registries for crosses are maintained by the CBHS and CBHS Australasia (Fig. 6-14).


The Morgan horse gained its name from one phenomenal stallion named Figure, who later became known as Justin Morgan, after a former owner. The breed is regarded as the first American Breed, with Figure’s birthplace believed to Springfield, Massachusetts. The present-day Morgan stands between 14.1hh and 15.2hh. The Morgan is easily recognized by his proud carriage, upright graceful neck, and distinctive head with expressive eyes. Deep bodied and compact, the Morgan has strongly muscled quarters. The intelligence, willingness, zest for life, and good sense of the Morgan are blended with soundness of limb, athleticism, and stamina. Morgans can be registered with the American Morgan Horse Association (AMHA) (Fig. 6-17).

Quarter Horse

The Quarter horse originated in the United States during the colonial era and was developed for racing the quarter mile. The breed has a refined head with a straight profile that is distinctively shorter and wider than that of the Thoroughbred. They usually stand between 14hh and 16hh. The horses are compact and well muscled. The underline is longer than the back. The quarters are muscular. Horses of the breed can be registered with the American Quarter Horse Association (AQHA). The Quarter horse is one of the most popular breeds in the United States and has the largest breed registry in the world (Fig. 6-23).

Color Associations


The Palomino cannot be granted true breed status because of the variations in size and appearance. Therefore, it is classified more as a color than a breed; however, horses can be registered in the Palomino Horse Association, Inc. (Fig. 6-24).

FIGURE 6-24 Palomino pony.

Common Pony Breeds

Pony of America

The breed originated from the efforts of one man, Leslie Boomhower of Mason City, Iowa. The breed standard calls for a pony that had the appearance of a miniature Quarter Horse/Arabian cross, with Appaloosa coloring and some of that breed’s features. They usually are between 11.2hh and 13.2hh tall. All of the ponies are inspected before full registration is issued to ensure that they meet the breed specification. Emphasis is given to substance, refinement, and a stylish straight, balanced action marked by notable engagement of the hocks under the body (Fig. 6-26).

The Miniature Horse

Miniature Horse

Many of the miniature horses have several breed influences, but the Falabella is one of the main influences founded in South America. The miniature horse cannot exceed 34 inches in height measured from the last hairs of the mane. The breed should be small, sound, and well balanced and should have correct conformation. Refinement and femininity should be seen in the mare. Boldness and masculinity should be seen in the stallion; the general impression should be one of symmetry, strength, agility, and alertness. Horses of this breed can be registered with the American Miniature Horse Association (AMHA) (Fig. 6-29).


The normal reproductive course for any large animal species is discussed in Chapter 3. Table 6-1 lists specific equine breeding information. The following reproductive procedures are variations that exist among species. Figure 6-32 illustrates the equine estrous cycle.

Equine Female Reproductive System

Some diseases of the female reproductive tract are unrelated to breeding and reproduction and require diagnostic procedures and medical or surgical treatment. However, the overwhelming majority of female reproductive system procedures are performed on breeding animals, with the ultimate goal being delivery of a live foal. Unlike their counterparts in other species, successful breeding and pregnancy in female horses is not often easy to accomplish. In order to produce a live foal, the following must occur:

• Successful breeding: Mares do not always readily accept the male. Also, timing of insemination (natural or artificial) must correspond to the time of ovulation, which may be difficult to determine. The source of the semen (the stallion) may not be at the same location as the female, requiring that the semen be shipped to the mare or that the mare be shipped to the stallion’s farm for breeding.

• Successful conception.

• Successful implantation: The period from conception to implantation is prolonged in horses; implantation begins approximately on day 35. Embryonic losses are high during the time before implantation.

• Successful gestation: Gestation in the horse averages 330 to 345 days.

• Successful parturition: The placenta begins to separate early during the delivery process; deprived of this oxygen source, foals rarely survive dystocias that last more than 1 hour.

• The foal must still survive the delicate neonatal period. Veterinary medicine is often involved in each of the earlier steps. Coupled with the economics of the breeding industry, breeding mares can be a tricky and expensive business.

Owners frequently have additional concerns about breeding mares early during the breeding season. Mares are seasonally polyestrous. They have estrous cycles from early spring to fall and are anestrous during the late fall and winter months. This means that, under natural conditions, horses usually breed and conceive in the spring and summer and deliver about 11 months later—in spring or early summer. In certain horse breeds, all horses born in a calendar year are considered to be the same age and must compete against each other, regardless of the month they are born. It is advantageous to have foals born early in the year so that they will be bigger and stronger than foals born in late spring or summer of the same year. This is especially important in the racing breeds. Larger body size and muscle mass may also be considerations in horse show halter conformation classes in some breeds that value heavier muscling (e.g., Quarter Horses, Paint Horses, Appaloosas). If a mare fails to breed successfully or has an early embryonic loss, the mare will not cycle again for approximately 3 weeks. If she is bred again, an embryo can be detected by ultrasound only after almost 2 weeks. If several unsuccessful attempts are made to breed and conceive or if time is taken to treat a uterine infection or other disease, the month is now May or June, and the resulting foal (if successful conception does occur) would be born “too late” the following year to be competitive.

One approach to compensate for the naturally short breeding season is the use of artificial lighting. Artificial lighting during winter months can “fool” the mare’s system by increasing the photoperiod to which she is exposed, resulting in winter estrous cycles. This is done to create a longer breeding season, usually so that foals can be born as early the following year as possible. A longer breeding season also allows more time for repeated attempts to breed and conceive in case something goes “wrong.” Artificial lighting is provided beginning in December in gradually increasing increments until 16 total hours of light exposure per day is achieved. Most mares respond with estrous cycles beginning in January or February.

Female Reproductive Examination

In the female, rectal palpation and ultrasound examination of the ovaries, uterus, and cervix are performed. A visual examination of the vagina and cervix is usually done, followed by uterine culture and possibly endometrial (uterine) biopsy. The results of the examination allow the veterinarian to assess fertility, identify potential conditions that might interfere with successful breeding, and diagnose venereal diseases.

Uterine Culture

The most common cause of infertility in the mare is uterine infection with bacteria. Mares with uterine infection generally have difficulty conceiving and supporting a pregnancy. Unlike other domestic species, uterine infections in horses are usually clinically “silent,” with minimal or no external signs such as vulvar discharge or irritation. Systemic illness with signs of septicemia and fever also is unusual. Most infections are fairly superficial in the uterine lining, and the bacteria do not gain entry into the bloodstream in significant numbers (the notable exception is uterine infection after foaling; after foaling, the separation of the placenta exposes many blood vessels in the uterine wall, and bacteria can gain ready entrance into the bloodstream). Therefore, the only clue that a mare may have uterine infection is repeated unsuccessful breedings, either failing to conceive or conceiving and losing the embryo early in pregnancy. This usually prompts the client to call a veterinarian.

Performing a uterine culture can confirm the presence or absence of uterine infection (Box 6-3). Sensitivity testing can also be performed to guide proper antibiotic therapy. Some breeders culture mares routinely at the beginning of the breeding season so that early treatment of “dirty” mares can be pursued.

A uterine culturette is used to obtain the culture. Culturettes are commercially available and are generally about 24 to 30 inches in length. They consist of an outer protective plastic sleeve and an inner cotton-tipped swab. Most have a guarded tip, which is a “trap door” cap that prevents contamination of the swab as it is passes through the vulva, vagina, and cervix. Once the culturette is in the uterus, the veterinarian presses forward on the swab and the tip opens to let the swab tip through.

Uterine Infusion

Infusion is a method of delivering liquids into the uterus (Box 6-4). Indications for the procedure include the following:

The volume of liquid infused depends on the underlying reason for the infusion. It may range from less than 100 ml for inseminations to several gallons in the case of postfoaling lavage. For uterine lavage, the goal is to remove debris and exudates from the uterus; therefore, the fluids are usually removed by siphon or internal massage. For administration of antibiotics and for insemination, the goal is keep the infused material in the uterus. Mares often attempt to expel the infused material by assuming a urination stance and straining. If the infusion is intended to stay in the uterus, the mare should not be allowed to assume this position. Walking the mare briskly for several minutes after uterine infusion may help prevent this from occurring.

Endometrial (Uterine) Biopsy

Biopsy of the lining of the uterus is done to evaluate the histologic condition of the endometrium, usually as part of an assessment of a mare’s fertility (Box 6-5). The endometrium contains the endometrial glands, which support and nourish the embryo. The endometrium is also the site for implantation and development of the placenta. Uterine infections, trauma from foaling, and aging may cause abnormalities such as atrophy of the endometrial glands, fibrosis around the glands, and inflammation, which can interfere with the mare’s ability to support pregnancy. Biopsy allows a histopathologist to examine the condition of the endometrium and assess the probability of the mare being able to support a pregnancy. The histopathologist usually assigns a grade of 1, 2, or 3 to the specimen, with grade 1 representing a normal or minimally abnormal specimen, grade 2 representing mild to moderate pathology, and grade 3 representing severe or irreversible pathology.

The endometrial biopsy is only one piece of information used to evaluate fertility; it is not the only criterion used to assure or condemn a mare’s future as a breeding animal. Some mares with grade 1 uteruses cannot maintain a pregnancy; likewise, mares with grade 3 uteruses have been successfully bred. The biopsy is only part of the puzzle and is best used as a management tool for breeding.

The biopsy is obtained with a 70-cm long (≈28 inch) stainless steel uterine biopsy forceps (Fig. 6-33). The forceps should be sterilized. The forceps have alligator jaws and can obtain a tissue sample approximately 1.5 mm long and 4 mm wide. It may be necessary to use a small syringe needle to carefully retrieve the sample from the forceps jaws. Once retrieved, the sample is placed in a liquid fixative. The technician should consult the laboratory for the preferred method of fixation. Common fixatives include Bouin’s fixative, 10% buffered formalin, and 70% alcohol. Samples should not sit in Bouin’s fixative for more than 24 hours.

Semen Collection in the Stallion

Artificial vaginas (AVs) are most commonly used to collect from stallions. Most collections are made into a handheld AV while the stallion mounts a mare in estrus (“jump” mare); however, some stallions can be trained to mount and ejaculate into an inanimate mounting dummy mare (“phantom”). Phantoms can be adjusted to a comfortable height for the stallion and reduce the risk of injury to the stallion from unwilling mares. The AV can be built into the phantom.

The technician wears gloves and prepares the stallion by washing the penis with warm water. The stallion is usually encouraged to have an erection by exposing him to a mare in heat, and the penis is cleaned while the erection is maintained. If a jump mare is being used, she also needs to be prepared. The tail should be wrapped or bandaged, and the perineal area should be washed with antiseptic scrub and clean water. Usually the mare needs to be restrained to prevent injury to the stallion and personnel. A twitch is commonly used, and sometimes hobbles are placed around the hindlimbs to prevent kicking.

The actual collection procedure is potentially dangerous. Breeding behavior in horses is usually aggressive and sometimes violent, and personnel are in vulnerable positions. Many facilities require personnel to wear helmets. The procedure requires a minimum of one person to handle the mare, one to handle the stallion, and one person to perform the collection into the AV. The usual method is to restrain the mare, then lead the stallion to approach the mare from her left side. The stallion is allowed to mount the mare, and the semen collector quickly moves in to grasp and divert the penis into the AV before it can enter the mare. The hands are then used to stabilize the AV alongside the mare while the stallion ejaculates. The AV is aimed slightly downward so that the ejaculate flows into the collection bottle (Fig. 6-34).

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Aug 11, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Equine Husbandry

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