PS4-11. Influence of Arginine Supplementation on Follicular Activation and Energy Metabolites in Serum and Histotroph.

Abstract Primiparous cows experience decreased conception rates during their second breeding season as they partition available energy to lactation and growth over reproduction. Arginine is an amino acid that is semi-essential during reproduction due to its biological activity in the uterus and influence on follicular activation via the mTOR pathway. Thus, arginine supplementation may influence metabolic and reproductive physiology during early gestation in beef cattle by altering uterine environment and increasing follicular activation. The objective of this study was to evaluate the effects of arginine supplementation on antral follicle count (AFC) and non-esterified fatty acids (NEFA) and glucose in serum and histotroph of primiparous beef cows. Thirty-one primiparous Angus x Hereford cows grazing native rangelands were randomly assigned to 1 of 2 treatments: 1) cattle supplemented 180 mg/kg body weight arginine + dried distiller's grains with solubles (DDGS) at 0.0067% of body weight (ARG; n = 16), or 2) cattle supplemented DDGS at 0.0104% of body weight (CON; n = 15). Supplements were formulated to be isonitrogenous and to meet or exceed nutrient requirements for growth and lactation. Cows were on trial for a total of 48 d and received supplement three times per week for the first 30 d. On d 20 of supplementation, cattle underwent estrus synchronization using the 7-d CO-Synch+CIDR protocol followed by fixed time artificial insemination on d 30. After the supplementation period, uteri were flushed for collection of histotroph on d 42 and 47, corresponding to d 12 and 17 of gestation, respectively. Blood samples were collected on d 0, 30, 42, and 47, and histotroph and serum were analyzed for NEFA and glucose concentrations. Antral follicle counts were conducted on d 0 and 48 for pre- and post-treatment comparisons. Data were analyzed using PROC MIXED in SAS (v9.4). The model included fixed effects of treatment, day, and treatment ´day, with repeated measures used for analysis of AFC and serum metabolites. Treatment did not influence serum NEFA concentrations (P = 0.49), but serum NEFA were increased on d 30 and 42 relative to d 0 and 47 (P = 0.02). Serum glucose concentrations were not influenced by treatment, day, or treatment ´ day (P ≥ 0.69). For histotroph, there was no difference in NEFA for any of the effects analyzed (P ≥ 0.47). However, glucose concentrations in histotroph were significantly affected by day (P < 0.001), being greater on d 17 than on d 12 of gestation with no effect of treatment (P = 0.33). Antral follicle counts were not affected by treatment, day, or treatment × day interaction (P ≥ 0.81). In conclusion, arginine supplementation during the pre-breeding period did not alter circulating or uterine metabolites or AFC in primiparous beef cows.