Breeding Soundness Exams

A breeding soundness exam, or BSE, is a necessary and practical expense for both breeder or buyer. They are done on both mares and stallions, and include a battery of tests to determine the breeding status of the animal, and health of the reproductive and endocrine systems.

Often when purchasing a mare, the buyer will, and should, do a vet check. Although the mare may not be purchased for the intended purpose of reproduction, she may be harboring reproductive problems that could impede her performance career. These may include cystic ovaries, uterine infections, chronic or otherwise, hormonal imbalances, and vaginal windsucking to name a few. For this reason, we recommend a BSE in addition to physical exam, blood work and x-rays, when investing in any mare.

Pre season BSEs need to be addressed as early as November for the Febuary breeder. Often when finding a manageable problem, it can take time to identify and alleviate. If waiting until February, you can lose valuable weeks of your season before your mare is “clean.” As example, if a biopsy is found to be necessary, you would not breed on that cycle, but wait for the next. Time lost can mean the decreased value of a foal born later in the season.

A breeding soundness exam, may consist of all, or a combination of tests. These would depend on the mare’s age, breeding status, and history. The history is quite important, and if at all possible, should be presented first, to the vet preforming the BSE. Examples of this background would include:

  1. Has she been previously bred.
  2. How many live foals delivered.
  3. Any foaling problems.
  4. How many cycles to settle.
  5. Any early embryonic loss.
  6. Average length of estrus cycle.
  7. Abortions, and at what stage of pregnancy.
  8. Previous treatment for uterine infection.
  9. When was her last foal.

The exam commences with a visual exam of the mares vaginal conformation. This includes the vulva, perineum and anal area. As mares age, and this is certainly more prevalent with certain breeds, the vulva, normally vertical, tips, creating a recessed anus. This gives the vulva a shelf effect, and allows dropping manure to contaminate the area, in turn allowing bacteria to find entrance to the vaginal tract. The opposing lips should not sag or gap. If they do not seal, the mare will aspirate air, predisposing her to uterine infection. This condition is called Pneumovagina. A procedure called a Caslick, effectively corrects this. It is a simple suturing of the external vulvar lips. Mares in race training are routinely Caslicked when they enter training. This is to alleviate them from windsucking, common during speed work. Without the Caslick, they are predisposed to vaginal, uterine and endometrial problems, in turn, affecting performance. Caslicks are removed shortly before parturition, in the bred mare. Open mares are often Caslicked, as routine, to keep them clean until the next season.

Your vet will then move on to the internal exam. A rectal palpation is used to check the status of her ovaries, possible follicles, uterus, uterine tone and cervix. Pregnancy status is also confirmed. The ovaries are kidney bean shaped and can range in size from a marble to a golf ball. Hard, smooth, small ovaries are indicative of anestrus and, or a hormonal imbalance. Ovarian tumors can create an oversized ovary. The vet is looking for follicular activity, either a pre-ovulatory follicle or a corpus luteum. These would indicate normal estral activity.

Moving on to the uterus, which consists of a body and opposing horns, forming a Y or T formation. It is checked for size, symmetry of the horns, and abnormalities. These may include possible tumors, atrophy of the endometrial folds, or lymphatic cysts, to name a few.

The final area to check is the cervix. Physically it is a tube like structure that connects the vagina to the uterus. It is of vast importance to the reproductive efficiency of the mare. During diestrus, (non heat) or pregnancy, it is closed and firm. During estrus, it softens and dilates to allow passage of the ejaculate or insemination. If the mare loses the ability to close and keep the cervix sealed, she will abort. Damage to the cervix can come through difficult foal delivery, rendering tears and scar tissue. To check the cervix, the vet will additionally do a visual check, by placing a vaginal speculum into the vagina. Using a flashlight, the entire vaginal canal can be inspected. Scarring and tears to the cervix can be observed along with possible pooling of fluid or urine.

Specimens are now collected. A uterine endometrial culture and cytology are routine. These are done with the introduction of a swab into the uterus, and the samples grown and examined for uterine infection, and the presence of microorganisms. The cytology is a study of the actual cells for evidence of contamination, yeast, fungi, etc.

An endometrial biopsy is the best method of evaluating the mare as a potential broodmare. It uses a category system for prognosis.

1. Class 1:
2. Class 11A:
3. Class 11B:
4. Class 111:
80 – 90% chance of carrying to term
50 – 80%
10 – 50%
Less then 10% chance of carrying to term

An alligator type uterine forceps, introduced vaginally, extricates a small piece of endometrial tissue. Most serious problems, that can adversely affect a mare’s fertility, can be detected only by these samples, under a microscope.

Additional information can be obtained with the use of transrectal ultrasound. One of the best uses of ultrasound, in a BSE, is it’s ability to “see” fluid accumulation within the uterus. Another excellent diagnostic tool is blood work. Non physical problems in mares are often the result of inefficiencies of the Endocrine system. It is these glands that are the brain of the entire reproductive factory. Without the proper hormonal stimulation, there can be reproductive shutdown. A hormonal assay is a quick, inexpensive diagram of your horses reproductive fuel source.

Stallions too should receive a yearly exam. As a stallion ages, he goes through physical changes. After age 13, you may see signs of testicular degeneration. Before considering a stallion for purchase, breeding, or pre season re-evaluation, a BSE would include:

  1. Penile cultures, including Urethra, pre and post ejaculation, Fossa Glandis, and semen culture
  2. Semen collection and evaluation for Progressive Motility, Concentration, Volume, Morphology, Longevity, Velocity, Extenders
  3. Testing for STDs
  4. Testicular palpation, with ultrasound if necessary
  5. Check Orientation of testicles
  6. Daily sperm production VS Daily sperm output
  7. Hormone analysis

Additional visual observations of the BSE include; Signs of testicular degeneration, Libido, Number of mounts, Ability to maintain erection, Mount without difficulty, Physical ability to thrust, Ability to ejaculate sperm.

It is possible for a stallion to hold back sperm, ejaculating only seminal fluids. This is often caused by previous breeding and/or collection mismanagement, but can also be physical. Stallions who do so can become “accumulators” and develop blockages. In most cases these can be eliminated through repeated, multiple, daily collections.

It is unfortunate that culturing stallions at the onset of each breeding season, is not a prerequisite of breeders. Stallion owners demand clean cultures and cytologies of mares to be bred, and mare owners should do likewise. Mare owners have every right to inquire as to a stallion’s breeding soundness exam, and current status. Whether a stallion had a good past season, is not necessarily an indication of the current one. Mares may be high tech, high maintenance, factories, but stallions are not machines.

Annual pre season breeding soundness exams are good horse sense, good business sense, plus outstanding preventative medicine. Talk to your vet early to prepare for your coming breeding season. Discussing and implementing a program, including early breeding soundness exams, will help you realize your reproductive expectations, and put you on the road to a successful endeavor.


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