The Impact of Divergent Nutritional Planes in Mature Bulls on The Subsequent Immune Response to Improve Reproductive Efficiency

Bull fertility is a major component of reproductive efficiency. One of the many factors that influence reproductive efficiency is bull nutrition. Improper nutrition will influence both bodyweight (BW) and body condition scores (BCS) but also increase systemic and local stress which can alter the molecule composition of seminal plasma that could impact the uterine response to mating and thus pregnancy outcomes. Elucidating how seminal plasma from the ejaculate influence the uterine immune response could aid in understanding the variation of pregnancy rates. Mature Angus bulls (n = 10) were utilized to create one of three seminal plasma (SP) treatments 1) nutrient restricted and frozen (RES) 2) maintenance nutrients and frozen (MNT), or 3) maintenance nutrients and fresh (FRESH). Non-lactating cyclic mature beef females (n = 24) were used to complete the objectives of this study. to 7.5) were utilized in a crossover (n = 18) experimental design with a control subset (n = 6) to complete the objectives of this study. This design resulted in three sample pathways which corresponded to the order in which they were exposed to infusion of SP (RES/MNT or MNT/RES or FRESH) for 2 uterine flush sequences. The experiment evaluated the influence of nutritional plane in bulls and SP infusion in cows on systemic immune score (SIS) of serum samples and cytokine concentration within uterine luminal fluid (ULF) and SP. Systemic immune score was influenced by treatment with greater (P < 0.001) SIS in the RES bulls (0.03 ± 0.003) compared to the MNT (0.003 ± 0.003) and FRESH (-0.003 ± 0.003) bulls. Cows infused with FRESH SP had a greater concentration of IL-6 (P < 0.01) compared with RES and MNT groups. Cows infused with RES SP tended to have greater concentrations of VEGF-A (P = 0.06) and had an increased concentration of MCP-1 (P = 0.04). Interferon-γ, IL-36RA, MIP-1β, and IL-10 had greater concentrations during the first treatment flush sequence compared to the control and second treatment flush sequence. Understanding the influence sire nutrition can have on the uterine environment following mating could aid in creating a more receptive environment for pregnancy establishment.