Zoologic Classification

Following is the zoologic classification of horses.

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.

BOX 6-1   Terminology

Mare	Female after third birthday
Broodmare	Female being used for breeding
Stallion	Intact male between 2 and 3 years of age
Gelding	Castrated male of any age
Foal	Young horse, from birth to weaning (usually 4–7 months old)
Weanling	Young horse, from weaning to first birthday
Yearling	Horse 1– years
Long yearling	Horse –2 years
Colt	Intact male between 2 and 3 years of age
Filly	Female between 2 and 3 years of age

Common Equine Instruments

The accompanying Evolve website contains pictures and descriptions of common equine instruments.

Anatomical Terms

Figures 6-1 to 6-2 will help you review the terms for body parts and areas of horses as well as the names of bones and joints.

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).

Clydesdale

The Clydesdale originated in the Clyde Valley, Scotland. The breed typically stands around 16.2hh, although some are larger and can weigh up to a ton. The legs often appear long and have abundant silky feathering. The joints should be big, the hocks broad and clean, knees flat, and neck long. Cow hocks are a breed characteristic and are not viewed as a fault. Colors are usually bay or brown, but grays, roans, and blacks are also found. Leg and facial markings are common in this breed (Fig. 6-4).

Percheron

The Percheron originated in the Perche region of Normandy. The horse on average stands 16.2hh. The body is broad and deep chested. The head is pleasing, with a broad square forehead, straight profile, and large mobile ears. The neck is long and arched in the top line. The withers are more prominent than in most heavy breeds and allow for considerable slope in the shoulders, which is reflected in their free-moving action. The legs are short and powerful. The hooves are hard, blue horn, with little feathering on the lower limbs. The usual colors are dappled gray or black, but occasional bay, chestnut, and roan are also accepted (Fig. 6-5).

Shire

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).

Suffolk Punch

The Suffolk Punch developed in East Anglian county. Every Suffolk can trace its descent to a single stallion, Thomas Crisp’s Horse of Ufford. The average height for a Suffolk is 16hh to 16.3hh. Its gaits are distinctive. The hindlegs must be close together, and cow hocks are rarely found. The quarters are huge, rounded, and powerfully muscled. The breed has a strongly crested neck, and the forearms are very muscular with good bone and minimal feathers. All Suffolks are “chestnut.” The Suffolk Horse Society, formed in 1877, recognizes seven shades, ranging from a pale, almost oatmeal color to a dark, almost brown shade. The most usual is a bright, reddish color (Fig. 6-7).

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).

Technician Note

The three specific coat patterns within the American Paint breed are overo, tobiano, and tovero.

Andalusian

Andalusian horse breeding is still centered in the province of Andalusia in southern Spain. The average height for an Andalusian is 15.2hh. The horse has a commanding presence with lofty and spectacular paces. The facial profile is convex, and the eyes are almond shaped. It has a natural balance and a rather sloped croup (Fig. 6-11).

Appaloosa

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).

Technician Note

The seven basic coat patterns within the Appaloosa breed are blanket, blanket with spots, roan, roan blanket, roan blanket with spots, spots, and solid.

Arabian

The origin of the Arabian is unclear, but there is evidence that it existed on the Arabian Peninsula around 2500 bc and was maintained there in its pure form. The body is compact, the back is short and slightly concave, and the croup is long and level. The legs are long, slender, hard, and clean, and the tendons are clearly defined. The head tapers to a very small muzzle with large flared nostrils. The mane and tail hair are fine and silky. During movement the tail is carried arched and high. A dished forehead is common in the breed (Fig. 6-13).

Technician Note

It is common to see a dished forehead on horses of Arabian descent.

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 Hackney and Hackney Pony

The Hackney derives from the famous trotting “Roadsters” of Norfolk and, to a lesser extent, the Yorkshire Roadsters, which shared a common ancestry with the Norfolk breed. The Hackney typically stands between 14hh and 15.3hh. The hocks are set closely to the ground, the shoulders are exceptionally strong, and the withers are low. The Hackney pony shares the same stud book but is truly a pony. It stands up to 14hh but shares the same characteristics found in the Hackney horse (Fig. 6-15).

Missouri Fox Trotter

The Missouri Fox Trotter originated with the settlers from Kentucky, Tennessee, and Virginia who made their home in the Ozark Hills of Missouri. The body is well muscled, fairly deep, and noticeably wide. Although usually sufficiently compact, it may have some length in the back. The chest is wide and deep. The shoulders are strong, and the breed has rounded withers. The breed stands on average between 14hh and 16hh tall. The predominant coloration is chestnut in all shades, usually with white markings, although any color is accepted (Fig. 6-16).

Morgan

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).

Paso Fino

The Paso Fino, originally from Puerto Rico, is a gaited breed related to the Peruvian Paso. The average height is 14hh to 15hh. The breed has a muscular chest. The neck is short and upright but well muscled (Fig. 6-18).

Tennessee Walking

The Tennessee Walking horse evolved in the state of Tennessee in the mid-19th century. The breed is deep bodied and short-coupled, with a head that tends to be rather plain. It carries its head much lower than a Saddlebred, and the horse moves with far less elevated action. The breed stands between 15–16hh. Predominant colors are black and all shades of chestnut, sometimes with prominent white markings (Fig. 6-19).

American Saddlebred

The American Saddlebred originated in the American South and was initially called the Kentucky Saddler. The principal breeding area is still the Kentucky’s Bluegrass Country around Lexington. The horse typically stands around 16hh. The quarters are smoothly muscled with a near-level croup and a high-set tail. The hindlegs despite length in the shanks, are well formed, with long musculature, clean hocks, and flat, hard fetlock joints. The neck is long and elegant; its juncture with the withers ensures a distinctively high carriage in movement. The head is neat and fine with no fleshiness through the jowl (Fig. 6-20).

American Standardbred

The American Standardbred was first established in the eastern states of the United States. Its body is long and low but is still powerful and deep through the girth. The overall build is powerful. The croup usually is higher than the wither to give enormous propulsive thrust to the quarters. It has strong forearms. The head is plain but not unattractive. It is, however, heavier and less refined than that of the Thoroughbred (Fig. 6-21).

Thoroughbred

The Thoroughbred first evolved in England during the 17th and 18th centuries. The body is typically long in its proportions. The quarters and the loins are strong. The hindlegs are long. The forearms are fine, long, and muscular. The head is refined and alert with no hint of fleshiness in the jowl. It blends into a long, gracefully arched neck that in turn joins symmetrically with the shoulders. The shoulders are long and very well sloped with prominent withers (Fig. 6-22).

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).

Technician Note

The American Quarter Horse has the largest breed registry in the world.

Color Associations

Palomino

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).

Technician Note

Horses can be dual registered if they belong to a color association as well as a breed association.

Pinto

The name Pinto comes from the Spanish pintado (“painted”). The primary difference between a Paint and a Pinto is this: All Paints are Pintos, but not all Pintos are Paints. This is a good guideline, because the Paint registry’s primary criteria are those of bloodlines rather than color, whereas the Pinto association’s criteria are primarily concerned with color and not bloodlines.

Although there is a Pinto association, the Pinto cannot be granted true breed status because of the variations in size and appearance (Fig. 6-25).

Technician Note

All Paints are Pintos, but not all Pintos are Paints.

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).

American Shetland Pony

The breeding of the American Shetland pony was originally centered in the state of Indiana, following the large importations of ponies from the Scottish Shetland Islands that began in 1885. The pony typically stands up to 11.2hh. The withers are unusually prominent for a pony and contribute to the slope of the shoulder. The girth is a good depth and the legs are longer than in other ponies (Fig. 6-27).

Welsh Pony

Welsh ponies belong firmly to the Principality of Wales. For centuries they have been bred on the hills and uplands. The Welsh pony can be classified into four sections—A, B, C, and D—with A being the smallest and D being the tallest. Ponies across all four sections can vary in height from 12hh to 15hh. The Ponies stud book is located with the Cob stud book. The pony has a flowing outline that is symmetrical and balanced in its proportions. It is full of quality and pony character. The forelimbs are long and well-muscled. The head shows Arabian influence (Fig. 6-28).

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).

Technician Note

Miniature horses cannot exceed 34 inches in height.

Donkeys and Mules

The donkey or ass is domesticated member of the Equidae family. A male donkey is called a jack. A female donkey is called a jenny (Fig. 6-30).

A mule is a cross between a male donkey and a female horse. A hinny is a cross between a female donkey and a male horse. Almost all mules and hinnies are infertile and unable to reproduce. A female mule that has an estrous cycle is called a molly. A molly can occur naturally or can be accomplished through hormone manipulation. Mollies have short thick heads with long ears and come in a variety of colors (Fig. 6-31).

Reproduction

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.

Technician Note

The period from conception to implantation is prolonged in horses. Implantation begins approximately on day 35.

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.

Technician Note

• All horses’ birthdays are January 1 for competition purposes.

• Mares are seasonally polyestrous. They have estrous cycles from early spring to fall and are anestrous during the late fall and winter months.

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.

Technician Note

Uterine infections in horses are usually clinically “silent,” with minimal or no external signs.

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.

BOX 6-3   Uterine Culture

Equipment

• Sterile OB sleeve or sterile rectal sleeve

• Vaginal speculum and light source

• Sterile water-soluble lubricant (KY Jelly)

• Uterine culturette

• Culture medium or transport tube

Procedure

The mare is restrained and the tail held or tied away from the perineum. The perineal/vulvar area is prepped routinely. The veterinarian may pass the culturette either manually, with the hand in a sterile plastic sleeve, or visually through a vaginal speculum. The uterine culturette is passed through the cervix and used to swab the lining of the uterus. Once the culturette is withdrawn, the cotton swab tip is collected and used for standard bacterial culture procedures. To avoid contaminating the swab, the guarded tip can be cut off or held out of the way. The cotton tip is commonly broken or cut free from the culturette stick and placed into a sterile glass tube or culture medium for transport to the laboratory. If transportation to the laboratory is delayed, the swab may dry out, killing the bacteria. Adding a small amount of sterile saline to the swab and refrigeration may delay drying.

Analysis of the sample commonly includes an air-dried smear for Gram staining as well as culture plating on blood agar and a gram-negative culture medium. Plates are incubated at 37°C (98.6°F) and checked daily for growth. Some practitioners request quantification (number of bacterial colonies) in addition to bacterial identification.

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:

BOX 6-4   Uterine Infusion

Equipment

• Sterile OB sleeve or sterile rectal sleeve

• Vaginal speculum and light source

• Sterile water-soluble lubricant

• Disposable uterine infusion pipette

• Fluid line (standard intravenous [IV], arthroscopy, or bell IV)

• Sterile 60-ml syringes

• Infusion fluids

Procedure

The mare is restrained and the tail held or tied away from the perineum. The perineal/vulvar area is prepped routinely. The veterinarian gives the infusion by passing a uterine infusion pipette (or a fluid line) through the cervix into the uterus, similar to the procedure used for artificial insemination. Infusion pipettes may be passed either manually, with the hand in a sterile plastic sleeve, or visually through a vaginal speculum. Once the pipette or fluid line is in position, the fluids are delivered by attaching either a syringe or fluid line connected to the infusion fluids. Gravity flow or pressurized flow may be used. Immediately following the infusion, the mare is walked briskly for several minutes if the infused material is intended to remain in the uterus.

• Treatment of uterine infection, in which antibiotics are diluted in a sterile solution (e.g., sterile saline or lactated Ringer’s solution) and infused into the uterus; this can be repeated daily for several days

• Routine flushing (lavage) of the uterus after an abortion or after foaling

• “Postbreeding” infusion to prepare the uterus to receive an embryo

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.

BOX 6-5   Endometrial Biopsy

Equipment

• Sterile OB sleeve

• Sterile water-soluble lubricant

• Sterile uterine biopsy forceps

Procedure

The mare is restrained and the tail held or tied away from the perineum. The perineal/vulvar area is prepped routinely. This is a two-step procedure. First, the veterinarian places the biopsy forceps through the vagina and cervix, into the uterus. The hand is then withdrawn from the vagina and reinserted into the rectum. Second, with one hand in the rectum and the other hand controlling the biopsy instrument handles, the instrument is positioned against the uterine wall and the tissue sample obtained. The mare may experience temporary discomfort when the sample is snipped. The instrument is then withdrawn, and the tissue sample placed in the proper fixative. No special aftercare is required.

Technician Note

Uterine biopsies are graded as 1, 2, or 3. A grade of 1 suggests a normal or minimally abnormal specimen.

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.

Technician Note

Bouin’s fixative is commonly used for biopsy samples. It consists of 10% buffered formalin and 70% alcohol.

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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