Historically, mares have one of the lowest average conception/birth rates of any of the domestic species (somewhere in the neighborhood of 60-70%). Excellent breeding and overall management of mares and the blessing of high-quality semen from a fertile stallion can result in higher rates on many farms, but in general, the enjoyment and thrill of successfully breeding a mare often are accompanied by some frustration and disappointment when she fails to settle right away, resorbs the fetus, or aborts a celebrated pregnancy. With an eye toward identifying potential chances for success or reasons for failure, many mares are presented to a veterinarian for a breeding soundness examination (BSE). The BSEs most often are performed on mares as part of a pre-purchase evaluation, for infertility work-ups, prognostically prior to urogenital tract surgery, or as a matter of routine on all open or maiden mares prior to the next breeding season (in the latter case, the benefit of identifying a problem and correcting it prior to the start of the next breeding season is obvious).

An example of poor vulvar conformation. Photo by Christine Schweizer, DVM

The mare BSE, in general, includes the recording of a thorough and detailed history, an overall physical examination and a detailed examination of the reproductive tract. The latter would include an assessment of perineal conformation and health, rectal palpation, ultrasound of the cervix, uterus, and ovaries, a vaginal examination, a uterine culture and cytology, and a uterine endometrial biopsy. Other ancillary diagnostics also can be performed as indicated