Endometritis, or inflammation of the uterus, is a common cause of reduced fertility in mares. Although you usually think of endometritis in the older mare, Dr. John Hurtgen from Pennsylvania indicates that young mares, especially those that have had racing or performance careers, are also susceptible. The reason is these mares achieve a high level of fitness in their athletic careers and lose body fat in the perineal area. This allows the rectum to be displaced forward and increases the chance of vulvar contamination with feces. Many fillies will subsequently aspirate air and feces in the vagina and this can lead to infection.

Many trainers also give fillies progesterone to keep them out of heat and this also increases the chance of a uterine infection developing. Racing fillies usually have a surgical procedure performed on their vulva called a Caslicks surgery to prevent this contamination. As far as older mares, many of them over 8 to 12 years of age have some uterine problems. These problem mares can be identified by ultrasound prior to breeding as many of these mares have excessive uterine fluid that is detrimental to pregnancy. Also, the cervix of many of these mares fails to dilate and this contributes to the buildup of fluid. Manual dilation of the cervix and coating the cervix with a prostaglandin paste can be beneficial in treating these cases. Also, the administration of oxytocin 4 hours after breeding will aid in decreasing uterine fluid and these injections can be continued even after ovulation. Join us on our next program for more on endometritis in mares.