The incidence of fluid in the post ovulatory area and in the early corpus luteum in the mare

Abstract

Summary Mares were examined during oestrus for ovulation. The interval between pre- and post ovulatory observations varied between 30 minutes and 48 hours. The presence of anechoic fluid spaces in the post ovulatory area or early CL was recorded at examinations made up to 6 days after ovulation. The incidence and diameter of fluid spaces was analyzed for five groups of mares where the pre- and post ovulatory examination interval was 30 minutes to 6 hours, 6 1/2 to 11 hours, 12 to 18 hours, approximately 24 hours and approximately 48 hours. Fluid was seen in the post ovulatory area more frequently in the period 0 to 6 hours after ovulation than at other times in the first 24 hours. This fluid was considered to be residual follicular fluid which was either still present during a prolonged evacuation phase or was permanently retained. The diameter of the fluid space did not exceed 20 mm and in most cases was very much less. Total evacuation of fluid occurred in over 90% of cases. Formation of new fluid spaces didnot occur until after 24 hours. Fluid spaces were found in 54% to 58% of CL's 48 hours after the time of the detection of ovulation. Permanent lacunae in CL's examined 2 to 6 days after the detection of ovulation were found in about 43% of cases. Lacunae of 30 mm or larger werenot found until at least 36 hours after the estimated time of ovulation. Follicular hemorrhage and partial follicular collapse can be differentiated from normal ovulation by the retention of a large area of follicular fluid. By examination every 24 hours these conditions can be diagnosed with accuracy. When the interval between examinations is 48 hours, follicular hemorrhage may still be diagnosed but partial follicular collapse may only be suspected by an unusually large lacuna at this time. At examination in mid dioestrus the luteinized follicle resulting from these abnormal conditions may be indistinguishable from a normal CL.