The effect of endophyte infected tall fescue and isoflavones on rumen microbial populations and beef cattle production in Tennessee
Melchior, E. A., J. T. Mulliniks, G. E. Bates, J. K. Smith, and P. Myer.  2016.  UT Beef and Forage Center Graduate Research and Poster Symposium, UT Beef and Forage Center Annual Research and Recommendation Meeting. Knoxville, TN.

Tall fescue is the most common forage utilized by beef cattle operations in the state of Tennessee. Despite the nutritive benefits tall fescue provides, negative impacts on production can occur with the infected endophytic fungus Acremonium coenophialum. Consumption of the endophyte often results in the condition fescue toxicosis. This condition is characterized by several symptoms including decreased weight gain and conception, depressed feed intake, increased blood pressure and body temperatures. Periods of extreme environmental stress cause animals to exhibit more pronounced symptoms leading to an unthrifty appearance. These symptoms manifest in decreased productivity which costs beef producers across the United States over $1 billion annually. Despite the key role ruminant microbial communities have on digestion, there has been limited research on the effects of the ergot alkaloid ergovaline, the predominant causative agent on these microbial communities. In an effort to decrease the effects of the endophyte, clovers are often mixed into a pasture for a dilution effect. While this forage management technique has proved useful to producers, not much is known about the potential toxicosis-mitigating molecular mechanism that exists with clover. Isoflavones, compounds found in clover, have shown to decrease effects of fescue toxicosis when added to the diet. In the proposed study, in vitro and in vivo models will be conducted to determine if consumption of endophyte infected tall fescue with or without the addition of isoflavones induces microbial population shifts, altering rumen function. In a heat-stressed environment, cattle will be utilized in a GrowSafe feed monitoring system to measure individual feed intake of one of four different treatments: (1) endophyte infected tall fescue, (2) non-endophyte infected tall fescue, (3) endophyte infected tall fescue with isoflavones, or (4) non-endophyte infected tall fescue with isoflavones. Each of these treatments will be fed for three weeks. Rumen fluid samples will be taken prior to and at the conclusion of each treatment period. Behavioral traits such as movement, feeding durations, and feeding interval differences will be recorded throughout each treatment. Determining the impact of endophyte infected fescue on the microbial ruminal environment and the effect of supplemental isoflavones in the diet may provide future beef producers management options to alleviate symptoms of fescue toxicosis.