Findings of Reproductive Organs from Parturition to the First Luteal Stage and Fertility in Postpartum Mares

Abstract

Ultrasonic monitoring was made on the uterus and ovaries of 14 mares from parturition to the first functional luteal stage. The conception rate was investigated about 7 mares mated at the first postpartum estrus. The foal heat appeared 7-12 days after parturition in 9 of 14 mares and ovulation was seen 9-15 days after parturition in 12 mares while 22 and 35 days after parturition in the remaining 2 mares. With the estrous signs the ultrasonic image of the uterus cavity revealed prominent endometerial foldings with star-like layering of the folds during 3-7 days, which disappeared 1-2 days before ovulation. There were 5.2 follicles (1-3 cm in diameter) on average 3-4 days after parturition, and 1 or 2 of them attained 4.3-5.2 cm in diameter at the ovulation. Out of 7 mares 4 and 3 mares were successfully mated during and after the presence of the starlike layering of the folds image, and 3 mares were fertilized.