Differences in longissimus thoracis metabolites in feedlot steers with differing plasma Zn concentration and implant status

This study examined the role of Zn status on muscle glucose and other metabolites. Angus steers (144; 525 ± 30 kg) with varying plasma Zn concentrations and implant status were used for this secondary experiment. Steers were assigned to implant (IMP) treatments: no implant (NO) or Component TE-200 (TE-200; Elanco, Greenfield, IN) on d 0. Zinc sulfate was supplemented at 0 (analyzed 54 mg Zn/kg DM), 30, or 100 mg Zn/kg DM starting d -60. Steers were fed in two blocks via GrowSafe bunks, and steer was the experimental unit. Jugular blood and longissimus thoracis biopsies were collected d 40 post-implant. Plasma Zn was quantified via ICP-OES and stratified into quintiles by concentration and IMP treatment. Samples (n = 48; 12 low and 12 high from each IMP group) were identified and designated to plasma Zn treatments (PLZN): low (LO, 1.1 mg Zn/L) or high (HI, 1.6 mg Zn/L). Corresponding muscle samples were analyzed via gas chromatography-mass spectrometry for non-targeted metabolomics. Data were analyzed using ProcMixed of SAS with fixed effects of PLZN, IMP, BLOCK, and PLZN×IMP. No interactions were noted. β-alanine, 3-hydroxybutyric acid, and glycine were greater in HI than LO ( P ≤ 0.05), while 3-hydroxybutyric acid, 2,3,4-trihydroxybutyric acid, and glycine were greater in TE200 than NO ( P ≤ 0.03). Lactic and malic acids tended to be greater in TE200 than NO ( P ≤ 0.10). Although both Zn groups were adequate, greater plasma Zn altered metabolites indicative of enhanced energy metabolism, potentially explaining benefits of Zn supplementation to feedlot cattle.