Reproductive biology of the mare: oestrous cycle and ovulation time

Abstract

Twenty one mares were used, 11 Pure breed (PSA) and 10 cross-breed Arabicus (CA) from 3 to 11 years old. The animals were teased daily. The heat was supervised by rectum palpation at first twice, and thereafter, three times a day until the end of estrus. Independent of estrus stage, all animals were examined three times a week. To detect the ovulation time, the mares were examined at 8:00 am, 4:00 pm and 11:00 pm, through the whole estrus period, to observe the ovarian and follicles size, sensibility and consistency. The mean length of oestrous cycle was 24.24 ± 6.00 days, with 7.50 ± 4.16 days to estrus and 17.53 ± 3.18 to diestrus. The ontset of estrus occurred more frequently at 12:00 pm than at 8:00 am or 4:00 pm. Ovulations occurred at night (75%) and 25% during the day. Ovulations were frequently uniform in the ovariums. In 85% of the cases the estrus signs finished 24 hours after ovulation.