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:

  • Accurate identification of the mare
  • Recording of the mare's breeding and foaling history
  • Physical examination and evaluation of the perineal (vulvar) conformation
  • Palpation and ultrasonography of the reproductive tract
  • Endometrial (uterine) swab for microbial culture
  • Speculum exam of the vagina and cervix, and digital exam of the cervix
  • Biopsy sample of the endometrium (lining of the uterus)

    Reasons to perform this exam include:

  • Barrenness or history of infertility
  • Pre-purchase examination
  • History of previous foaling complications or injuries
  • Recent abortion

    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:

  • Well recorded teasing and breeding records may allow us to determine whether breeding management was appropriate. One should keep in mind that poor breeding management, such as breeding mares at the wrong time during their cycle and/or with poor quality semen, is probably the most common cause of infertility.
  • Young maiden mares (mares never bred before) should not require a complete BSE before entering a breeding program, unless an obvious abnormality is detected during routine examination prior to breeding. Bridging the vagina and/or uterus in an otherwise seemingly normal mare will not yield any valuable information and may induce a uterine infection.
  • A different situation occurs when purchasing an old maiden mare (>15 years) for breeding purposes only, in which case the BSE may yield important information regarding the health of the endometrium (uterine lining) and hence the chances for the mare to carry a foal to term. Typically, it can be expected that older mares will have some degree of subfertility; this is either manifested by low pregnancy rates or by increased frequency of pregnancy loss (miscarriage). These mares often have problems such as air sucking or urine pooling in the vagina due to poor perineal conformation and loss of tone (sagging) of the reproductive tract. Additionally, old mares will have aged oocytes (eggs), less suitable of becoming properly fertilized or of developing into a normal fetus.
  • A barren mare that has been bred but that has never become pregnant, may have a congenital (from birth) abnormality of the reproductive tract such as hypoplastic (small) ovaries, abnormal development of the uterus or hydrosalpinx (blockage of the Fallopian tubes or oviducts). In mares with congenital anomalies, a sample of blood and/or skin should be sent to the laboratory for karyotyping, or chromosomal analysis.
  • A barren mare that was bred last season but is not going to deliver a foal this season, although she has produced a foal sometime in the past, may have a uterine infection (endometritis) or degenerative changes of the endometrium (i.e. uterine lining). A history of dystocia (difficult foaling) should prompt the veterinarian to check for cervical, vaginal and perineal (vulvar) scars or tears.

    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.

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