International Symposium on Ruminant Physiology: One-carbon metabolism in beef cattle throughout the production cycle.

One-carbon metabolism (OCM) is a series of connected pathways involving the methionine-folate cycles, transsulfuration, polyamine synthesis, nucleotide synthesis, free-radical scavenging, and energy metabolism. These pathways functionally depend on AA (methionine, glycine, and serine), vitamins (folate, B, B, and B), and minerals (sulfur, cobalt, and zinc). Growing bodies of research indicate that in beef cattle, physiological stage, nutritional plane, diet, species (Bos taurus vs. Bos indicus), rumen protected versus not, individual versus combination supplementation, and method of delivery all affect the efficacy of one-carbon metabolite supplementation. Infusion studies showed that supplementing methionine to growing steers improved N retention and altered hepatic activity of methionine synthase; however, only supplementing methionine without folate decreased folate concentrations in circulation. When heifers were supplemented with methionine, choline, folate, and B for the first 63 d of gestation, metabolomic analysis revealed increasing OCM analytes to the heifer, but a buffering effect to the fetus, with minimal changes seen in hepatic metabolite abundance. Methionine supplementation to heifers during the periconceptual period increased circulating methionine but shifted fetal hepatic metabolism toward the transsulfuration pathway. Periconceptual methionine supplementation to cows increased gain and total-tract digestibility in calves post-weaning. In vitro supplementation of choline to beef cattle embryos results in calves of increased birth and weaning weight. Overall, these data demonstrate that OCM is altered in those cattle receiving one-carbon metabolites, and that a metabolic programming response is elicited in offspring receiving supplements in vitro or during early gestation. Research should be considered to maximize efficiency of beef cattle production at all stages by identifying limiting metabolites or enzymes to maximize efficiency of OCM in beef cattle, as well as to understand the concerted effects of multiple one-carbon metabolites to balance the stoichiometry of the pathway.