Ovulation rate and distribution in the Thoroughbred mare, as determined by ultrasonic scanning: the effect of age

Abstract

Ovarian activity was monitored in 2181 oestrous cycles from 1136 thoroughbred brood mares to accurately determine overall ovulation rate, the relative distribution of ovulations between left and right ovary, whether mare age had an effect on these parameters and whether ovulation pattern in one cycle affected the pattern within the next. Ultrasonic scanning was used in preference to rectal palpation and slaughterhouse material due to its greater accuracy. Mare’s ages ranged from 3 to 22 years. The results obtained indicated a similar incidence of ovulation occurring on the right (49.5% of all ovulations) or left ovary (50.5%). Multiple ovulations (MO) occurred in 22.4% of oestrous cycles. Significantly (P