Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle

Authors: MELCHIOR, E - UNIVERSITY OF TENNESSEE; SMITH, J - UNIVERSITY OF TENNESSEE; SCHNEIDER, L - UNIVERSITY OF TENNESSEE; MULLINIKS, J - UNIVERSITY OF TENNESSEE; BATES, G - UNIVERSITY OF TENNESSEE; Flythe, Michael; Klotz, James; JI, H - UNIVERSITY OF TENNESSEE; GOODMAN, J - UNIVERSITY OF KENTUCKY; LEE, A - UNIVERSITY OF TENNESSEE; CALDWELL, J - UNIVERSITY OF TENNESSEE; MYER, P - UNIVERSITY OF TENNESSEE

Submitted to: Translational Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2018
Publication Date: 12/29/2018
Citation: Melchior, E.A., Smith, J.K., Schneider, L.G., Mulliniks, J.T., Bates, G.E., Flythe, M.D., Klotz, J.L., Ji, H., Goodman, J.P., Lee, A.R., Caldwell, J.M., Myer, P.R. 2018. Effects of endophyte-infected tall fescue seed and red clover isoflavones on rumen microbial populations and physiological parameters of beef cattle. Translational Animal Science. 3:316-328. https://doi.org/10.1093/tas/txy147.
DOI: https://doi.org/10.1093/tas/txy147

Interpretive Summary: Symptoms resulting from tall fescue toxicosis are responsible for over $2 billion in losses for beef cattle producers across the United States, including reduced reproductive performance and reduced overall gain and feed efficiency. It has long been recognized that cattle perform better on tall fescue when clovers are included in the pasture. Previous research determined that natural compounds, called isoflavones, in red clover can reverse some of the negative effects of fescue toxicosis. The toxic compounds in tall fescue cause blood vessels to constrict, and blood flow is impeded. The isoflavones do the opposite, they cause blood vessels to relax and blood flow to improve. The current study supported the earlier results by showing that cattle that were challenged with fescue toxins over a 21-day period performed better when they also received red clover isoflavones. The impact of this work is confirmation that feeding isoflavones to ruminants may be a viable option for alleviating symptoms of fescue toxicosis and promote livestock growth and performance.

Technical Abstract: The toxic endophyte within tall fescue is responsible for vasoconstriction, reduced serum prolactin and reduced production in cattle. The inclusion of mixed forages into pastures, especially red clover, has shown to mitigate some of these effects. Clovers contain phytoestrogenic compounds such as isoflavones, which may play a role in reducing these symptoms. The present study utilized forty Angus steers to determine if daily supplementation with a red clover-isolated isoflavone feed additive would reduce the symptoms of tall fescue toxicosis at a physiological level and within the rumen microbial environment over a 21-day period. Cattle were stratified among treatments based upon their single-nucleotide polymorphism genotype at the DRD2 receptor. Treatments were conducted as a 2×2 factorial arrangement, consisting of tall fescue seed type (endophyte-infected tall fescue seed vs endophyte-free tall fescue seed) supplemented with isoflavones and without the isoflavone feed additive. Serum prolactin concentration was decreased with consumption of endophyte infected tall fescue seed, but was greater with supplementation of isoflavones. Average daily gain was reduced with consumption of endophyte-infected tall fescue, indicating an acute period of fescue toxicosis was reached. Twenty-six ruminal bacteria taxa shifted as a result of treatments.