Ultrasonographic characteristics of the follicular and uterine dynamics in belgian mares

Abstract

Summary Changes in the follicular development and visualiza- tion of endometrial folds during the estrous cycle were characterized by ultrasonography in Belgian mares. The secondary follicular wave was observed in only 2 of 7 mares and began in early diestrus (day 1; day 0 = day of ovulation). The dominant follicle of the ovulatory primary wave was retrospectively detected on 8.1 ± 3 days after the day of ovulation (day 0 = day of ovulation). The largest subordinate of the primary follicular wave was first de- tected at day 7.6 ± 1.6. The endometrial folds were most prominent 6.6 ± 1.3 days before ovulation. Regression of the endometria] folds was observed to occur 5.5 ±1.5 days before ovulation. In conclusion Belgian mares appear to have follicular dynamics similar to those reported for Thoroughbred horses. The cyclic uterine changes observed with ultrasound were more sudden, could only be observed for a short period of time and were observed earlier in relation to ovulation when compared with observations made in other breeds.