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Breeding Soundness Examination of the Mare

By: Dr. Sylvia Bedford-Guaus

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Physical Examination and Perineal (Vulvar) Conformation Evaluation

The mare breeding soundness examination (BSE) should always include a complete physical exam. Undernourished and obese mares may have problems becoming pregnant, carrying to term or foaling. Mares with physical problems, especially those causing severe pain such as laminitis (founder) usually have cyclicity problems and seldom become pregnant. Endocrine diseases, such as Cushing's, may affect reproductive cyclicity or predispose breeding mares to uterine infections.

Perineal conformation evaluation is especially important in older mares. A competent, tightly closed and properly shaped vulva will protect the reproductive tract from ascending infections. In older and undernourished mares, lack of muscle tone and fat around the perineal area may result in the upper part of the vulva being sunken forward, instead of perpendicular to the ground. This defect predisposes to problems such as fecal contamination of the vestibule or vagina, air sucking and urine pooling. Poor vulvar conformation may also be linked to incompetence of the vestibulo-vaginal sphincter (ring of tissue that separates the vestibule from the vagina), predisposing these mares to vaginal or uterine infections. Such problems can be corrected with relatively simple surgical procedures suited for each specific defect.

While evaluating the mare's external genitalia it is also important to note any discharges coming through the vulvar lips that may be an indication of a reproductive tract infection.

Palpation and Ultrasonography of the Reproductive Tract

The ovaries and uterus of the mare are examined by palpation and ultrasound through the rectal wall, since the reproductive tract (ovaries, uterus, cervix and vagina) is located in the pelvic cavity just below the rectum. For this purpose, the mare should be restrained in stocks or held with her rear end against the opening of a stall door. A nose twitch or sedative may be used if deemed necessary to minimize risks of injury for both the veterinarian and the mare. The veterinarian's arm is suited with a well-lubricated disposable plastic sleeve and inserted into the rectum of the mare. Feces must be carefully removed from the mare's rectum prior to the exam.

Palpation (feeling) of the mare's ovaries allows the veterinarian to ascertain their shape and relative size. Palpation of both the ovaries and uterus can help the veterinarian estimate the stage of the estrus cycle, based follicular activity and the tonicity (hardness) and shape of the uterus and cervix. Abnormalities such as missing parts or masses (swellings) can be detected with this technique.

Ultrasonography is a much more sensitive technique to detect some changes of the reproductive tract such as uterine edema, cysts or fluid within the uterus:

  • Edema (fluid within the uterine wall), which gives the uterus a pinwheel or sliced orange appearance, is normally seen in mares in heat, but can otherwise be a sign of uterine inflammation and infection.

  • Cysts are fluid filled lymphatic swellings within the uterus that do not usually interfere with the mare's ability to conceive or carry to term. Only when extremely large or present in large numbers, do cysts interfere with the mare's ability to support the early embryo and predispose the mare to embryonic loss. Round small cysts can be easily confused with an early pregnancy (embryo) and thus should be carefully recorded when detected.

  • A small amount of fluid within the uterus may be a normal finding when mares are in heat. Large amounts of fluid or any amount of fluid in a mare that is not in heat is an abnormal finding usually consistent with endometritis (uterine infection). One should carefully interpret this finding together with the results of culture and biopsy to decide on the cause and course of treatment.

    Endometrial (Uterine) Culture and Biopsy and Other Specific Procedures

    Before bridging the reproductive tract (penetrating the cervix and entering the uterus) to obtain samples for culture and biopsy, two important objectives must be accomplished:

  • If there is any chance at all that the mare might have been bred, the veterinarian must make sure that she is not pregnant at the time of the exam, which is done through palpation and ultrasound exam of the uterus. Going through the cervix to take a culture or biopsy sample in a pregnant mare will induce pregnancy loss or abortion. It must be emphasized that pregnancy itself is one of the main reasons why bred mares do not show signs of heat.

  • Minimize contamination of the reproductive tract by wrapping the mare's tail and scrubbing the vulva and surrounding area with an antiseptic such as povidone iodine soap (Betadine scrub). After scrubbing, the vulva should be thoroughly rinsed with warm water and dried. Additionally, the veterinarian should always wear a clean sleeve and surgical glove when introducing the arm into the vagina of the mare.

    Maiden mares may bleed slightly when the vagina is bridged due to rupture of the hymen. This has no clinical importance and will resolve spontaneously.

    The combination of culture and biopsy will provide a very accurate representation of the reproductive health status of the uterus:

  • To minimize contamination of the uterus or sample, the culture is taken with a double guarded culture swab. This is a swab protected by two plastic sleeves, and therefore the swab itself is pushed forward and just exposed to the uterine lining once the whole device has been inserted through the cervix. The sample is appropriately packaged and usually sent to a laboratory for culture.

    Results of bacterial culture must be interpreted with caution and in accordance with clinical signs and biopsy results. A positive culture is not always indicative of endometritis (uterine infection) or the need for antibiotic treatment. Additionally, there is controversy as to using uterine swabs as screening techniques for premating diagnosis of endometritis, as requested in some stallion service contracts. In general, if the mare has no history suggesting a problem and an intact hymen, culturing maiden mares is unnecessary and if done careless may actually induce and infection in an otherwise normal mare.

  • The tissue sample for endometrial biopsy is taken with specially designed alligator forceps, placed in a tube with formalin (fixative) and also sent to the laboratory for processing and interpretation. If performed properly, this is not a painful or dangerous procedure for the mare and will not affect her future fertility. The tissue sample obtained is observed under a microscope and yields important information in regards to the presence of active inflammation (consistent with infection) or the presence of degenerative changes that will reduce the mare's capability to sustain an early pregnancy and carry a foal to term.

    As part of the exam, a speculum (sterile piece of plastic or carton tubing) is also introduced in the vagina. With the aid of a penlight, this allows visualization of abnormalities in the vagina such as inflammation (vaginitis), scar tissue, or pooling of pus or urine. To diagnose problems of the cervix the veterinarian must carefully feel the cervical canal with the fingers while the hand is inserted in the vagina of the mare. This is the only accurate way to diagnose problems such as old tears or scars resulting from previous difficult foaling. This procedure is more valuable if performed when the mare is not in heat.

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