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

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