LAUSR

The objective of this study was to evaluate the plasma metabolome of steers fed a Cu deficient or Cu adequate diet in response to a feed restriction (FR) challenge. Twenty-four Angus-cross steers (463 ± 29 kg) fed a common diet (4.5 mg Cu/kg DM) were utilized in a 2×2 factorial consisting of supplemental Cu concentration: 0 (CON) or 10 (SUPP) mg Cu/kg DM as CuSO4 and 5-d FR treatment: ad-libitum feed intake (AdLib) or restricted intake (RES-INT 50% of average pen DMI for 10 d prior). Steers were enrolled in a prior trial resulting in distinct liver Cu statuses of 6.7 ± 3.34 and 72.3 ± 26.6 mg Cu/kg DM for CON and SUPP, respectively. Steers were housed in pens (6 steers/pen) with GrowSafe bunks; steer was experimental unit. Steers were weighed at start and end of FR and plasma was collected at end of FR for non-targeted metabolomic analysis by GC/MS. Analyzed via Proc Mixed of SAS as a 2×2 factorial, DMI and ADG during FR were lesser in RES-INT than Adlib (P < 0.001), per design. Metabolites were analyzed in Metaboanalyst 4.0 by volcano plots, ANOVA, and significant analysis for microarrays with the fixed effects of Cu supplementation, feeding strategy, and the interaction. There were no interactions between Cu supplementation and feeding strategy (P > 0.99). Phenylalanine concentrations were greater (P < 0.001) while ornithine and glucose concentrations were lesser (P < 0.05) in SUPP vs. CON. Lactic acid concentrations were greater (P < 0.001), while heptadecanoic acid concentrations were lesser (P = 0.002) in Adlib vs. RES-INT. These data suggest that supplemental Cu concentration and feed restriction may alter the bovine plasma metabolome. Copper is required for phenylalanine metabolism, but further research is needed to fully evaluate the impacts of trace mineral status and feed intake on the bovine plasma metabolome.