Rumen and serum metabolomes in response to endophyte-infected tall fescue seed and isoflavone supplementation in beef steers

Authors: SEAY, TAYLOR - University Of Tennessee; MELCHIOR, EMILY - University Of Tennessee; CLEMMONS, BROOKE - University Of Tennessee; CORDERO, JUAN - University Of Tennessee; BATES, GARY - University Of Tennessee; Flythe, Michael; Klotz, James; JI, HUIHUA - University Of Kentucky; GOODMAN, JACK - University Of Kentucky; MCLEAN, KYLE - University Of Tennessee; MYER, PHILLIP - University Of Tennessee

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2020
Publication Date: 11/26/2020
Citation: Seay, T.B., Melchior, E.A., Clemmons, B.A., Cordero, J.F., Bates, G.E., Flythe, M.D., Klotz, J.L., Ji, H., Goodman, J.P., McLean, K.J., Myer, P.R. 2020. Rumen and serum metabolomes in response to endophyte-infected tall fescue seed and isoflavone supplementation in beef steers. Toxins. 12(12). Article 744. https://doi.org/10.3390/toxins12120744.
DOI: https://doi.org/10.3390/toxins12120744

Interpretive Summary: Tall fescue is the major forage used to feed cattle in pasture-based systems of the southeast and covers approximately 14 million hectares across the United States. The advantage of tall fescue is hardiness of the plants attributed to the presence of a fungal endophyte living in a mutualistic relationship with the plant. However, the endophyte produces ergot alkaloids that are toxic to animals that consume them for an extended period of time. Recent research has found that isoflavones, present in red clover may be responsible for reducing the effects of fescue toxicosis. Isoflavones act as on receptors present on blood vessels to promote vasodilation, reversing the effects of ergot alkaloid induced vasoconstriction and improving blood flow. The objective of the present study is to evaluate the effect of isoflavone supplementation with tall fescue seed consumption on beef steer’s rumen and serum metabolomes (the mixture of chemicals present in the blood or digesta). The rumen metabolome was largely impacted by seed type, while the serum metabolome was influenced by isoflavone supplementation. In the rumen, the impact of the seed type involved carbohydrate and nucleic acids metabolism. In the serum, differences in global metabolomes and individual metabolites involved in urea cycling and amino acid metabolic pathways were identified in animals receiving isoflavones and those who did not. This work supports the idea that dietary inclusion of isoflavones to reduce the harmful effects of tall fescue toxicosis.

Technical Abstract: Fescue toxicosis impacts beef cattle production via reductions in weight gain and muscle development. Isoflavone supplementation has recently indicated potential for mitigating these effects. The objective of the current study was to evaluate isoflavone supplementation with tall fescue seed consumption on rumen and serum metabolomes. Angus steers (n = 36) were allocated randomly in a 2×2 factorial arrangement of treatments including endophyte-infected (E+) or endophyte-free (E-) tall fescue seed, with (P+) or without (P-) isoflavones. Steers were provided a basal diet supplemented with fescue seed for 21 days, while isoflavones were administered daily. Following the trial, blood and rumen fluid were collected for metabolite analysis. Metabolites were filtered and extracted, then analyzed by UHLPC-MS. The MAVEN program was implemented to identify metabolites for MetaboAnalyst 4.0 and SAS 9.4 statistical analysis. Seven differentially abundant metabolites were identified in serum by isoflavone treatment, and eleven metabolites in the rumen due to seed type (P < 0.05). Pathways affected by treatments were related to amino acid and nucleic acid metabolism in both rumen fluid and serum (P < 0.05). Therefore, metabolism was altered by fescue seed in the rumen, however, isoflavone supplementation altered metabolism systemically to potentially mitigate detrimental effects of seed and improve animal performance.