Dietary Supplementation of Rumen-Inert Fatty Acids and Rumen-Protected Choline Modulates the Uterine Environment of Pregnant Beef Cows.

Early embryonic mortality is a major concern to the beef industry, as nearly 32.3% of multiparous cows will not maintain pregnancy past the first sixteen days of gestation. During this period, the uterine environment provides nutrients to support embryonic growth and development. Therefore, our objective was to (1) modulate the luminal metabolome at the onset of conceptus elongation in pregnant beef cows and (2) identify changes in the endometrial epithelial transcriptome during the peri-elongation period. Cows received either TARG: 100 g of a rumen-inert mono- and polyunsaturated fatty acid source plus 60 g of a rumen-protected choline source (n = 50) or CON: 114 g of a saturated fatty acid source (n = 50) daily from 30 days before (d -30) to 30 days after breeding (d 30). Uterine cytobrush was collected from pregnant cows on day 14 for metabolomics (CON = 17, TARG = 15) and on Day 16 for transcriptomics analysis (CON = 6, TARG = 7). On Day 14, the concentration of 23 metabolites (p < 0.1) differed; the concentration of fatty acids, triacylglycerols, hexosylceramides, cholesterol esters, phospholipids, biogenic amines, carboxylic acids, methyl donors, and amino acids was greater in TARG. On Day 16, 675 genes were differentially expressed (FDR ≤ 0.1). Among these genes, 506 genes were upregulated in TARG, involving important genes in pathways such as interferon signaling, fatty acid transport, synthesis, metabolism, immune response, and cell-to-cell adhesion. In conclusion, the dietary supplementation provided herein modulated the uterine environment during the period of conceptus elongation.