Influence of intrauterine saline infusion upon the oestrous cycle of the mare.

The effect of intrauterine saline on reproductive function was studied by infusion of mares in anoestrus, dioestrus, oestrus and prolonged dioestrus. Anoestrous mares were unaffected except near the beginning and end of the breeding season when anovulatory heats were induced. Dioestrous mares infused between Days 5 and 9 returned to heat an average of 3-8 days earlier than expected, and infusions during dioestrus were followed by ovulatory heats of normal fertility. Three mares in prolonged dioestrus showed ovulatory heats within 3 to 9 days of infusion. Infusions during oestrus had no appreciable effect. Repeated infusions were clinically harmless but post-infusion bacteriological swabs from the uterus were positive. In two cases studied, infusion was followed by a fall in peripheral plasma progestagen concentrations. Evidence was obtained that vaginal and cervical dilatation and oxytocin were not involved in the mechanisms and it is postulated that the luteolytic effect of intrauterine saline is mediated by prostaglandin.