Problems After Breeding

Breeding induces an inflammatory response in the uterus. The inflammation is a physiological reaction with the purpose of clearing the uterus from excess spermatozoa, seminal plasma, and bacterial contamination. Breeding-induced endometritis is transient and most mares resolve the inflammation within 24 to 36 hours. If a mare fails to resolve the breeding-induced inflammation before an embryo enters the uterus, the pregnancy is likely to be lost. Susceptibility to persistent breeding-induced endometritis occurs in approximately 15% of a normal brood mare population. Persistent breeding-induced endometritis can be diagnosed by ultrasonographic monitoring of the uterus for fluid accumulation at 6 to 24 hours after breeding. Mares that accumulate fluid beyond 6 to 12 hours after breeding, or have a history of persistent breeding-induced endometritis, should be treated with ecbolics and/or uterine lavage to help remove the inflammatory fluid from the uterus. Recent reports suggest that some mares with a history of severe breeding-induced endometritis may benefit from corticosteroid treatment around the time of breeding. Supplementation with exogenous progestin during early gestation may also be beneficial in mares with endometritis or other causes of secondary luteal deficiency.