PSII-27 Effect of endophyte-infected tall fescue seed and red clover isoflavones on the serum metabolites in beef steers

Fescue toxicosis reduces animal performance, costing approximately $2 billion dollars to the beef industry annually. Emerging research has demonstrated effects of fescue toxicosis can be reduced by consumption of red clover isoflavones. The objective of the current study was to evaluate the effect of isoflavone supplementation with endophyte infected seed consumption on serum metabolites in beef steers. Angus steers (n = 36) were randomly allocated to treatments in a 2×2 factorial arrangement of endophyte-infected (E+) or endophyte-free (E-) tall fescue seed, with (P+) or without (P-) a red clover isoflavone supplement. For the 21d trial, steers were provided a basal diet supplemented with fescue seed head targeting a minimum of 0.011 mg×kg of body weight−1×d−1 of total alkaloids. A total of 943 mg isoflavones were administered daily via bolus. Following the 21d trial, blood samples were collected for metabolite analysis. Metabolites were filtered from serum and extracted using 0.1% formic acid in acetonitrile:water:methanol (2:2:1) for analysis on the Dionex UltiMate 3000 UHPLC system and Exactive Plus Orbitrap MS. The Metabolomic Analysis and Visualization Engine program was used to determine peaks and identify metabolites. Resulting metabolite data were analyzed in MetaboAnalyst 4.0 and SAS 9.4 with significance at P≤0.05. Principle component analysis indicated separation of metabolomes between E+P+ and E-P- steers. Orthogonal partial least squares discriminant analysis depicted distinct separation between P+ and P- steers and partial separation between E+ and E- steers. The variation between P+ and P- metabolomes were mainly due to differences in citrulline (r = 0.47, P = 0.003), and AMP (r = -0.35, P = 0.03) between E+ and E- metabolomes. A total of 13 and 8 metabolic pathways were impacted from differences in seed type and isoflavone treatment, respectively (P ≤ 0.05). Therefore, metabolism is altered by isoflavone supplementation that may improve animal performance during fescue toxicosis.