Impacts of Red Clover Isoflavones on Tall Fescue Toxicosis in Beef Cattle

Endophyte-infected tall fescue [Lolium arundinaceum (Schreb)] is a cool-season perennial grass, commonly implemented by beef cattle producers. Tall fescue is one of the most utilized forages in the south east United States due to its performance as a forage, tolerance to poor soil conditions, and resistance to pests and environmental stresses. These attributes are possible due to the symbiotic relationship with an endophytic fungus, Epichloë coenophiala. However, negative impacts on cattle can occur when grazing tall fescue infected with the fungus, which produces toxic compounds known as ergot alkaloids. When cattle consume endophyte-infected tall fescue, the detrimental effects of the ergot alkaloids can result in fescue toxicosis, which can include reductions in reproductive efficiency, low average daily gain, high body temperature, vasoconstriction, and behavioral changes. These impacts on production contribute to an annual average of $2 billion in losses for beef cattle producers in the United States. To minimizes the negative effects of tall fescue toxicosis, legumes such as clovers have historically been mixed with tall fescue pastures. The positive impact of the addition of legumes to tall fescue pastures occurs through mitigation of fescue toxicosis due to dilution and concentration reduction of the ergot-alkaloids. Legumes contain phytoestrogenic compounds known as isoflavones, which have been demonstrated to provide beneficial effects on beef cattle experiencing tall fescue toxicosis, challenging the dilution theory. The objectives of the present studies were to determine a dose, a frequency, and the impact of isoflavones on beef cattle grazing endophyte-infected tall fescue pastures. The dose and frequency of isoflavones administered in the first two experiments did not have a significant impact on blood vasculature, rectal temperature, average daily gain, and ruminal bacterial taxa on cattle experiencing tall fescue toxicosis. Additionally, cattle undergoing isoflavone treatment did not have significant differences in blood vasculature, rectal temperature, average daily gain, and ruminal bacterial taxa compared to cattle grazing endophyte-infected tall fescue only. The isoflavone-dosage utilized on this project was not sufficient for cattle experiencing fescue toxicosis symptoms, and thus subsequent dose and administration studies should be conducted.