The postpartum period and dairy cow fertility Part 2: Ovarian function

摘要

After parturition, dairy cows have between two and five months to conceive again if they are to maintain sustainable productivity. The reproductive biological events that need to be completed to meet this objective are the restoration of the uterus toa receptive state that would support conception, and the return of ovarian cyclic activity with ovulation of competent oocytes. However, nearly half of all modern dairy cattle fail to ovulate the first postpartum dominant follicle and many have abnormaloestrous cycles, with anovulatory anoestrus, cystic ovarian disease or extended luteal phases. These abnormal oestrous cycles are often associated with exposure to stressors or insufficient dietary energy. Even when animals return to ovarian cyclic activity, many high-milk-yield animals have limited oestrus expression compared with cows studied 40 years ago. Finally, it is emerging that uterine disease can also perturb ovarian function. Understanding the mechanism of ovarian function postpartum may lead to more effective therapeutics and help veterinary surgeons consider strategies for improving the fertility of modern dairy cattle.