Maiden Mare Fertility

Q: I have a 12-year-old Quarter Horse barrel mare I would like to breed. She has never had a foal, and we have not been able to get her to settle after breeding her with cooled semen for three cycles. What could be causing fertility problems in an otherwise healthy mare?           Elizabeth

A: One of the most common fertility problems in a mature maiden mare is a cervix that fails to open properly. If a cervix is open and functioning normally, gravity and uterine contractions evacuate the majority of semen 12-18 hours after breeding. A tight, closed cervix causes retention of semen in the uterus that sets up an inflammatory reaction in the uterine lining.

A typical dose of cooled semen has approximately one billion sperm. Only about 3,000-10,000 cells make it to the oviducts. The uterine tissue recognizes semen as a foreign material and recruits white blood cells to clean up. Without normal evacuation of the balance of semen, the white blood cells start their clean-up function by releasing lysosomal enzymes, which are acidic. This acid environment damages the uterine lining, causing inflammation and fluid build-up. This inflammation recruits more white blood cells and creates more fluid build-up. By the time a fertilized egg comes down the oviduct, it lands in a hostile environment.

It is important to have your veterinarian check for this problem. A vaginal exam in an estrus mare (one in heat) should reveal a soft and pliable cervix. A diagnostic work-up should also include a uterine cytology and a bacterial culture.

If this is a problem in your mare, the recommended treatment plan is aimed at improving the drainage of the uterus. You might need to rest the uterus for 30 days to prepare for treatment. Older maiden mares have lower pregnancy rates if they are bred with frozen semen than younger maiden mares, and might not get pregnant. Therefore, it is best to breed older maiden mares with cooled or fresh semen.

When the mare is ready for breeding, PgE2 (Misoprostin) is placed on the cervix by your veterinarian to dilate the cervix. Breeding takes place three to five hours later. Four hours post-breeding, the uterus is lavaged with saline or lactated ringer's solution. In 24 hours, the uterus should be scanned and a treatment determined. If fluid is evident, lavage the uterus again. Administer Estrumate or oxytocin to stimulate uterine contractions and fluid evacuation. Antibiotics can be used when indicated. Do not give Estrumate after 36 hours post-breeding in order to preserve the ovary's corpus luteum (at the ovulation site; it produces progesterone to help maintain a pregnancy during the early stages).

In most mares, this treatment plan effectively decreases the length of time the inflammatory by-products remain in the uterus.

About the Author

Michelle LeBlanc, DVM, Dipl. ACT

Michelle LeBlanc, DVM, Dipl. ACT, is a theriogenologist (reproduction specialist) for Rood and Riddle Equine Hospital in Lexington, Ky. She was previously a professor in equine reproduction at the University of Florida. Her interests deal with mare infertility, embryo transfer, placental infections in mares, and acupuncture in infertile mares. She owns Thoroughbred/warmblood crosses and she competes in dressage.

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