Breeding Soundness Examination of the Mare

The breeding soundness examination (BSE) of the mare is a complete reproductive exam that should be performed by an experienced equine veterinarian in a systematic, accurate and thorough manner. The complete BSE should always include the following procedures:

Reasons to perform this exam include:

Additionally, a BSE should be performed in mares whose owners plan to invest in expensive assisted reproductive procedures, such as embryo transfer, or in mares to be bred with expensive transported (cooled) or frozen/thawed semen. A complete BSE need not be performed routinely in maiden mares entering a breeding program, unless pre-breeding palpation or ultrasound exam of the uterus reveals an obvious abnormality.

The BSE is NOT a test for fertility, but only a thorough exam that will allows speculation of the likelihood for a mare to become pregnant and/or carry a foal to term. The only true test for fertility is to breed a mare under good reproductive management conditions to a fertile stallion, and monitor if she becomes pregnant and delivers a healthy foal 11 months later.

Breeding Soundness Exams

A breeding soundness examination (BSE) should never be performed in a mare that cannot be accurately identified by branding, lip tattoos or breed registration records.

The breeding and foaling history should be carefully recorded since it is an essential tool to help ascertain if or why a mare is having fertility problems:

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:

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:

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:

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.

A mare does not pass or fail a BSE, but all results are pooled together to ascertain the likelihood of a mare to become pregnant and/or carry a foal to term, and to determine whether the mare requires any specific treatment prior to breeding. Some common problems that can be diagnosed during a routine BSE include:

The main problem associated with these changes is early embryonic loss, since the equine embryo depends on the secretions from the uterine glands until the placenta forms at 50 to 60 days of pregnancy. Please note that although these are chronic (long term), degenerative changes of the endometrium, the term endometriosis (exclusively a human problem) does NOT apply to horses. This term is mistakenly used in equine reproduction and often seen in horsemen and even veterinary oriented magazines, journals and textbooks.