Success when breeding older maiden mares depends on the management of several factors that contribute to the retention of excessive fluid in the uterus, including insufficient lymph drainage, a uterus hanging over the pelvic brim, and a tight cervix, according to Jonathan Pycock, B. Vet. Med, PhD, DESM, MRCVS, of Equine Reproductive Services, North Yorkshire, England. Pycock explained his approach at the AAEP Convention 2006.

"Unless your therapy program addresses all these problems, it’s going to end up not doing quite the job it ought to do," Pycock said. "If you’re going to come across one of these very susceptible maiden mares, it’s important to pull all the stops out the first time you inseminate her."

Semen causes an inflammatory reaction in the uterus, prompting the production of fluid to clear the uterus of the semen. However, in some mares, this fluid does not clear the uterus. The resulting inflammation decreases the chances of embryo survival. According to Pycock, it’s normal to see fluid in the uterus up to 12 hours following breeding, but some mares retain fluid beyond 24 hours. These mares require some special management in planning the breeding process, during breeding, and after breeding to have the best chance of pregnancy success.

To manage these mares, Pycock recommended practitioners understand how the uterus reacts to breeding and how therapeutic options will address this reaction, then formulate the best approach for their practices