Resumption of ovarian activity in postpartum period in dairy cow.

The selection of the first dominant follicle in postpartum period occures 7 to 15 days after calving. The resumption of ovarian activity is observed essentially in the ovary contra-lateral to the ex-gravid horn. One to three follicular waves are generally observed before the first ovulation in postpartum period. The first ovulation occures between 15 and 25 days postpartum without estrous behaviour and the resultant cycle is called <<ovarian cycle>>. The second cycle in postpartum period is associated with two (46 per cent) or three (54 per cent) dominant follicles. The second ovulation occures between 30 and 35 days postpartum. The subsequent estrous cycles are associated with three follicular waves and occures with overt estrous behaviour.