The equine breeding industry has evolved dramatically with the introduction of artificial insemination programs and advanced assisted reproductive techniques. While live cover breeding pro-grams are still a mainstay for specific breeds, many breed associations now accept foals conceived through the use of cooled and frozen semen, embryo transfer, and advanced techniques such as hysteroscopic insemination and oocyte transfer. The success of these breeding programs relies heavily on assistance from qualified equine veterinarians and even board-certified specialists in equine reproduction.

How can my veterinarian assist with breeding my mare? Before breeding season begins, an equine veterinarian with expertise in reproduction can assess the mare’s reproductive fitness, perform treatments or surgeries to prepare her for breeding, and provide advice about the optimal breeding program for an individual mare. With the choices available for breeding today, it is important to select the best method available (i.e., live cover vs. artificial insemination) for a given mare based on her age, physical condition, previous reproductive problems, and stallion availability. Your veterinarian can also give advice about stallion selection based on his reproductive history and semen availability (fresh, cooled, or frozen).

Once the breeding season is underway, a veterinarian with expertise in reproduction is essential for monitoring and timing the breeding. Exposing the mare to a stallion (teasing) is the best initial method for identifying signs of heat (estrus). But many mares live in performance barns without access to a stallion for teasing.

Examining the reproductive tract by transrectal palpation and ultrasound allows your veterinarian to determine if your mare is cycling, as the majority of mares are reproductively inactive in the winter. These tools also allow your veterinarian to determine the stage of the mare’s reproductive cycle once she begins cycling.

Reproductive examinations also help your veterinarian identify problems that might interfere with pregnancy, such as excess fluid in the uterus. Prompt treatment of problems optimizes the chance for pregnancy. Examination of the tract throughout the breeding cycle facilitates rapid identification of these problems.

How often will my veterinarian examine my mare for breeding? This depends on the type of semen used. If your in-heat mare is to be bred by live cover or cooled, transported semen, she will be examined frequently (every other day to daily) to determine the best time for breeding. Some veterinarians using frozen-thawed semen perform reproductive examinations several times a day to facilitate breeding as close to ovulation as possible. Many veterinarians have implemented timed breeding protocols with frozen-thawed semen with good pregnancy results. Using this protocol, the mare is inseminated with frozen-thawed semen 24 and 40 hours after administration of an ovulatory agent.

Your veterinarian also will want to document the day the mare ovulates after breeding. This examination allows him or her to know when to schedule your mare’s first preg-nancy exam for evidence of pathology (i.e., uterine fluid) or double ovulations. Mares normally don’t carry twin pregnancies successfully, so it is important to identify and manage twins early. Most veterinarians perform ultrasonographic examination of the reproductive tract for pregnancy (and twins) 14 days after ovulation. If twins are identified, one embryonic vesicle can often be eliminated so the remaining embryo can survive to term.

Where do I take my mare for specialized procedures? More specialized procedures, such as embryo flushing and transfer, hysteroscopic examinations or insemination, and oocyte transfer, are often done at a referral facility. These procedures are best performed by reproductive specialists with extensive experience. Referral reproductive specialists often work closely with ambulatory veterinarians to ensure optimal breeding management for these costly procedures. Understandably, the veterinarian who works most often with a mare can best predict the optimal time for breeding. Specialists can use that information to direct the timing of advanced reproductive procedures. A coordinated effort between the ambulatory veterinarian and the specialist is essential.

You can find veterinarians focusing on reproduction on the Society for Theriogenology website at Also, board-certified reproduction specialists can be found on the American College of Theriogenologists site at

About the Author

Margo L. Macpherson, DVM, MS, Dipl. ACT

Dr. Margo Macpherson, DVM, MS, Dipl. ACT, is an Associate Professor and Section Chief in Reproduction at the University of Florida. Dr. Macpherson is also a Diplomate and past president of the American College of Theriogenologists. She has a strong interest in placental disease of horses and is working toward diagnostic and therapeutic interventions that will improve neonatal survivability.

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