371 - Investigating Plasma Metabolomic Profiles at the Time of Weaning, Based on Pregnancy Outcome, in bos Taurus heifers

The objective of this study was to identify differences in the metabolomic profiles of heifers at the time of weaning based on their subsequent pregnancy outcomes. Angus/Simmental-cross heifers (n = 36) were weighed at weaning and 10ml of blood was collected. The blood plasma and white blood cells (WBCs) were isolated. Heifers were then assessed 30 days prior to artificial insemination (AI) for weight, pelvic area (PA), body condition scores (BCS) and reproductive tract scores (RTS). Reproductively mature heifers underwent an AI program with estrus detection and were then exposed to a bull two weeks after AI. Heifers were categorized into three groups: pregnant by AI, pregnant by natural breeding or open after 3 consecutive estrous cycles. 9 heifers pregnant by AI and 11 open heifers were chosen for metabolomic profiling. Of the 20 heifers selected, there was no difference in weight at weaning (355.6±21.9 kg AI, 364.2±33.3 kg Open, p >0.05), BCS (5.7±0.4 AI, 5.6±0.4 Open, P >0.05), RTS (4.1±0.6 AI, 4.0±0.7 Open, P > 0.05) or PA (173.7±10.8cm² AI, 175.6±9.1cm² Open, P > 0.05). Ten metabolites were found to be significantly up or down regulated in the heifers who remained open after three consecutive cycles, when compared to those pregnant by AI. Alanine, cystine, lysine, methionine, tyrosine, tryptophan and valine were down regulated while glycerol, fructose-6-phosphate and ribulose-5-phosphate were found to be up regulated in open heifers (P < 0.05). RNA isolated from WBCs was used to compare the expression of five inflammatory cytokines in the open and pregnant by AI groups (TNFα, IL6, CXCL5, POSTN and MCP1). Inflammatory cytokines were increased in all heifers that remained open after three consecutive cycles (p < 0.05). In summary, the quantity of specific metabolites present within the blood plasma are different at weaning between heifers with differing reproductive potentials. This could potentially be used to develop an assay to aid in selecting replacement females.