L-citrulline and L-arginine improve reproductive performance in primiparous and multiparous cows via distinct shared metabolic pathways and pyrimidine metabolism

Under the experimental conditions, L-Arg modulated the production of Dimethyl sulfone, 1,5-pentanediamine, Bassanolide, and Phenylalanine in primiparous cows through the protein digestion and absorption and ABC transporters pathways, while <i>L</i>-Cit influenced the same metabolites <i>via</i> the ABC transporters pathway. Both <i>L</i>-Arg and <i>L</i>-Cit promoted increased NO, GSH-Px, T-AOC, and VEGF levels, enhancing early embryo implantation. Additionally, <i>L</i>-Arg and <i>L</i>-Cit synergistically influenced pyrimidine metabolism, regulating the production of N-myristoylphosphorylcholine, N-oleoyl-d-erythro-sphingosylphosphorylcholine, 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine, and 1-docosahexaenoyl- 2-stearoyl-sn-glycero-3-phosphocholine. This modulation resulted in increased NO, GSH-Px, T-AOC, and VEGF in multiparous cows, ultimately supporting early embryo implantation.