The influence of intrauterine saline infusion on luteal function and cyclical activity in the mare.

Intrauterine saline infusion in the dioestrous mare shortened the ovulatory interval by inducing premature luteolysis. Plasma progestagen levels began to decrease approximately 1 day after the infusion and had declined to less than 1-0 ng/ml in 4 days. The CL, including others formed from ovulations during dioestrus, must be 4 to 5 days old before intrauterine saline will induce luteolysis. Of 10 mares infused on Day 4 or 5 after ovulation, only six had a shortened ovulatory interval. Of 10 mares infused on Day 6 or 7 after ovulation, seven had a shortened ovulatory interval and three failed to respond due to the occurrence of a dioestrous ovulation near the time of infusion. In those mares which responded to treatment, the interval from saline infusion to the beginning of oestrus and to ovulation was 5 to 6 days and 9 to 10 days, respectively.