413 Awardee Talk: Reproductive Efficiency: Managing Cows to Improve Reproductive Efficiency

Abstract

Abstract Management of a herd has a tremendous impact on reproductive efficiency, and estrous synchronization can be used as a tool to help get more animals to conceive early. In comparisons among synchronization protocols, pregnancy success did not differ between newer protocols. The factors that had the greatest impact on pregnancy success were estrous cycling status before the breeding season (estrous cycling > non-cycling; P < 0.01) and expression of estrus before fixed-time AI (estrual > non-estrual; P < 0.01). Thus, herd management, before the breeding season, has a large impact on reproductive success. Timing and type of vaccine used prebreeding can impact pregnancy success and luteal function (killed vaccine > modified live; P < 0.05). Nutritional changes can also impact reproductive efficiency. A decrease in available energy pre- (P = 0.05) or post-breeding (P = 0.02) decreased embryo quality (stage and grade, respectively) and subsequent concentrations of progesterone (P < 0.01). Cattle fertility is not only controlled by the female but is also controlled by the male. Stage of sexual maturity in bulls impacted scrotal circumference P < 0.0003), motility (P < 0.001), as well as mitochondrial membrane potential (P < 0.01), but stage of bull maturity did not influence viability, chromatin structure, nor amount of reactive oxygen species. Prenatal stress of a bull impacted the portion of sperm with DNA damage (control > prenatal stress; P = 0.04), but did not impact scrotal circumference, motility, mitochondrial membrane potential, or reactive oxygen species. Furthermore, sperm from bulls that were stressed in utero did not have differences in fertilization compared with control bulls; however, possible epigenetic modifications, to the sperm produced, resulted in fewer embryos making it to blastocyst stage (P = 0.03). Thus, management decisions made throughout the year can have a tremendous impact on reproductive efficiency and the percentage of animals that conceive early not only in the present breeding season but also in future breeding seasons as well.