Physiological and management advances enhancing adoption of applied reproductive management procedures in beef cattle

Abstract Text:

 Advances in research over the past two decades expanded our understanding of the bovine estrous cycle and led to improvements in methods to more effectively control estrus and ovulation in beef heifers and cows. Precise monitoring of ovarian follicles and corpora lutea over time by transrectal ultrasonography expanded our understanding of the changes that occur during a follicular wave. Consequently, we now know that precise control of estrous cycles requires the manipulation of both follicular waves and luteal lifespan. As a result, breeding management technologies are currently available or emerging that offer the potential to more effectively manage reproduction, expedite genetic progress, enhance efficiencies of production, and add value to beef cattle produced and marketed in the U.S. Until recently, the inability to predict time of estrus for individual cows or heifers in a herd was the primary reason beef producers viewed AI as being impractical to use because of the labor required to detect estrus. However, improvements in methods to control estrus and ovulation in beef heifers and cows provide the opportunity to expand the use of AI by reducing the period of time required to detect estrus or eliminate estrus detection entirely. Protocols for inducing and synchronizing a fertile estrus in which progestins are used strategically with gonadotropin releasing hormone and prostaglandin F2α provide opportunities for beef producers to synchronize estrus and ovulation and facilitate fixed-time AI. Procedures used to control estrous cycles in cattle include synchronization of estrus and ovulation in estrous cycling females, and induction of estrus accompanied by fertile ovulation in heifers that have not yet reached puberty or among cows that have not returned to estrus after calving. These strategies provide opportunities for producers to utilize sires of elite genetic merit, reduce length of the breeding and calving seasons, produce more uniform calf crops, and improve reproductive rates of replacement beef heifers and the mature cow herd. Collectively, advancements in applied reproductive technologies afford beef producers the flexibility to match specific breeding management protocols to a defined management system, thereby creating the opportunity to significantly expand use of AI in beef herds across the United States and enhance profitability of the beef enterprise.

Keywords: Estrus synchronization, fixed-time AI, beef