Endocrine regulation of bovine estrous cycle

Bovines suffer from inherent problems like late maturity, poor expression of estrus, irregular estrous cycle, seasonality in breeding, anestrous, low conception rate, long postpartum interval and repeat breeding which are the major constraints in livestock productivity and fertility. The different phases of reproductive cycle are regulated by intricate sequential events and interactions between hypothalamic releasing hormones, hormones secreted from the pituitary and sex steroids secreted by the ovary. Lack of integration or synchronization or endocrine imbalances at any phase of the sequence may result in reproductive failure. A sound knowledge of reproductive functioning in terms of interplay of hypothalamic, gonadotropic and gonadal hormones, with synergistic and antagonistic influences from other hormones and factors involved in the regulation of various reproductive stages, accurate oestrus detection, timely pregnancy diagnosis and early detection of nonconceived stock can be expected to lead to an improvement of the reproductive efficiency. Unravelling the secrets and myths of hypothalamo- hypophysial-ovarian axis will give a better understanding of reproduction in bovines.