Seasonal effects on female reproductive functions in the bovine (Indian breeds)

Abstract

Reproductive function is mediated by season in the Indian breeds of cattle ( Bos indicus ). The reproductive endocrinology of Bos indicus cattle differs from that of Bos taurus breeds; the estrus is shorter and less intense and occurs late in relation to an estrogen stimulus. Moreover, the Bos indicus female has a smaller preovulatory surge of luteinizing hormone (LH), which occurs earlier relative to the onset of estrus, and she ovulates sooner after the onset of estrus. The corpus luteum is smaller and contains less progesterone, and the serum progesterone concentration is lower in Bos indicus females. Furthermore, they have fewer preovulatory LH surges than Bos taurus females and their luteal cells are less responsive to LH in vitro during the winter. Their fertility is lower during the late fall and winter months. For Bos indicus cattle, recovery of transferable embryos and survival of embryos in the recipient are at their maximum from July through October.