Double ovulation rate of the first follicular wave follicles is higher in the first follicular wave dominant follicle in the ovary contralateral to the corpus luteum treated with human chorionic gonadotropin five days after estrus in lactating dairy cows

We examined the effect of human chorionic gonadotropin (hCG) treatment on double ovulation rate of first-wave follicles five days after estrus in lactating dairy cows. Cows were divided into two groups: 1) Ipsilateral group (IG; n=35), in which the first-wave dominant follicle (DF) was ipsilateral to the corpus luteum (CL), and 2) Contralateral group (CG; n=30), in which the first-wave DF was contralateral to the CL five days after estrus, then 1,500 IU of hCG was administrated. Double ovulation rate was significantly higher in the CG (26.7%) than in the IG (2.9%). This study demonstrate that the double ovulation rate of first-wave follicles was higher in the first-wave DF located in the contralateral ovary to the CL.