Strategies to Improve Reproductive Efficiency in Cattle with Dietary Intervention

This dissertation examines how reproductive efficiency can be improved through dietary intervention. The use of diet to enhance reproduction is theoretically a low-cost and low-input method that will co-align with reproductive technologies' beneficiary effects. Ideally, with improved nutrition intervention, these technologies will become more feasible and practical to producers. The first study examines the diet nutrient composition and its relative interactions on days to ovulation postpartum, overall pregnancy rates, and pregnancy at first AI in cattle. Most notably, the highest predicted overall pregnancy rate for multiparous cows was observed at high crude protein (CP), moderate non-structural carbohydrates (NSC), Low neutral detergent fiber (NDF) and high ether extract (EE). Additionally, the highest predicted pregnancy at first AI rate was when CP was high, moderate NSC, high NDF, and low EE. The second study examines the impact that a high starch diet may have on reproductive hormones, follicular growth, and pregnancy rates. The high starch diet tended to have a greater placental associated glycoprotein concentration, a greater number of large follicles on the day of breeding and a 20% numerically greater overall conception rate. The high fat diet did exhibit a greater number of medium sized follicles on the day of breeding. There were no observed differences in progesterone concentrations between the two treatment groups. The final study examines the effect that a higher starch diet might have on follicular development, CL growth and size, reproductive hormones, and insulin like growth factor binding proteins -2, -3, -4, -5, and pregnancy associated plasma protein A gene expression in granulosa cells. The experimental group that received the diet greater in starch exhibited a greater concentration of plasma IGF-1, greater number of large follicles on the dates that insemination would occur in a TAI situation, and a lower amount of days to reach a dominant follicle at the diameter of ≥ 10mm. Additionally, the high fat diet did exhibit a greater concentration of progesterone. Although, no statistical differences were observed in the granulosa cell gene expression and corpus luteum size. The feeding technique here may provide producers insight into non-expensive and straightforward ways to improve their reproductive efficiency and, ideally, adopt reproductive technologies in harmony with dietary intervention.