Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro

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; MCFARLANE, Z - University Of Tennessee; Flythe, Michael; Klotz, James; GOODMAN, J - University Of Kentucky; JI, H - University Of Kentucky; MEYER, P - University Of Tennessee

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2018
Publication Date: 10/18/2018
Citation: Melchior, E.A., Smith, J.K., Schneider, L.G., Mulliniks, J.T., Bates, G.E., McFarlane, Z.D., Flythe, M.D., Klotz, J.L., Goodman, J.P., Ji, H., Meyer, P.R. 2018. Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro. Animal Feed Science And Technology. 13(10): e0201866. https://doi.org/10.1371/journal.pone.0201866.
DOI: https://doi.org/10.1371/journal.pone.0201866

Interpretive Summary: Fescue toxicosis is a serious problem for cattle in areas where tall fescue is a predominant forage. The main problem in fescue toxicosis is an ergot alkaloid (nitrogen-containing compound) made by a fungus that inhabits the plant. Ergot alkaloids cause constriction of blood vessels, which impedes blood flow. However, ergot alkaloids and other components in tall fescue can have other effects. This experiment examined digestion of feed by microorganisms from the rumen. The first step in ruminant digestion is dependent on these microorganisms; therefore, their activity is essential to the nutrition of cattle and other ruminants. Some treatments also included isoflavones, another class of plant compounds from red clover. This comparison was made because red clover is often included in tall fescue pastures. It has been shown that red clover isoflavones are beneficial for growing ruminants, and that they reverse the blood vessel constriction caused by ergot alkaloids. The combined results of this study indicate some moderate rumen fermentation changes may have occurred due to treatments, but these results may have been affected by several factors. For one, the isoflavone concentration was low. These experiments used only about 2% of the isoflavones used in previous studies. These results emphasize that concentrations of plant and fungal compounds that impact one aspect of an animal's metabolism might not necessarily impact other metabolic functions. Careful dose studies are needed to separate the many biological activities of these forage plant compounds.

Technical Abstract: Ergot alkaloid pressure on livestock systems from consumption of endophyte infected tall fescue is responsible for over $2 billion in losses each year to producers. Evaluating the specific complications that arise from ergot alkaloid consumption has been studied for decades, but mitigation methods have not yet been clearly elucidated. Isoflavones found in red and white clover have been the subject of recent research regarding tall fescue toxicosis mitigation, but have yet to establish baseline concentrations that are effective. The aim of this study was to evaluate the effect of ergovaline and red clover isoflavones on rumen microbial populations, fiber degradation and volatile fatty acids in an in vitro system. Using a dose of 2.39 mg/L, endophyte-infected or endophyte-free tall fescue seed was added to ANKOM fiber bags with or without isoflavones in the form of a powder or pulverized tablet. Measurements of rumen pH, volatile fatty acids, bacterial taxa, as well as neutral detergent fiber, acid detergent fiber and crude protein were taken after 48h fermentation using the DAISY II system. NDF values were significantly altered by seed type and treatment (P < 0.05), and ADF values were significantly different among isoflavone treatments, as well as seed × treatment interaction (P < 0.05). Bacterial taxa were significantly different among groups (P = 0.03). Rumen pH values were not significantly different between treatments groups (P > 0.05). Isoflavones may be a viable use for mitigating tall fescue toxicosis, but further research should be conducted to determine physiological implications as well as microbiological changes in an in vivo experiment.