Control of ovarian follicular and corpus luteum development for the synchronization of ovulation in cattle

Abstract

The objective of this review is to integrate strategies to optimize an ovulatory control program which then serves as a platform to improve the reproductive performance of lactating dairy cows. Programmed management of follicle growth, regression of the CL and induction of ovulation led to development of the Ovsynch program. Pre-synchronization of estrous cycles followed 12 to 14 days later with the Ovsynch program increased pregnancy rates to timed inseminations. Initiation of the Ovsynch program on day 3 of the estrous cycle reduced ovulation to GnRH and resulted in a smaller proportion of excellent and good quality embryos following timed insemination. The pregnancy rate to a timed insemination of Ovsynch was greater when cows ovulated to the first injection of GnRH. The Presynch-Ovsynch program provided a platform to identify factors regulating reproductive performance; such as, parity, body condition score and anovulation. Treatment with hCG at day 5 after insemination increased pregnancy rate in lactating dairy cows. Injection of bovine somatotropin at insemination increased pregnancy rate, conceptus length and interferon-τ content in uterine luminal flushings and altered endometrial gene expression at day 17 of pregnancy. During heat stress, timed embryo transfer increased pregnancy rate and using embryos cultured with IGF-I and transferred fresh resulted in a greater pregnancy rate. Induction of ovulation with estradiol cypionate, as a component of a timed insemination program, increased fertility. Manipulation of the estrous cycle to improve follicle/oocyte competence and management of the post-ovulatory dialogue between embryonic and uterine tissues should enhance embryo development and survival.