Kentucky livestock farmers wondering whether to replace tall fescue pastures infected with endophyte fungus may want to consider research recently concluded by the University of Kentucky’s College of Agriculture and published in the prestigious Agronomy Journal.The research, led by Mary A. Marchant, professor of agricultural economics, suggests that in pastures where infestation levels of the endophyte fungus exceed 74 percent, it might be profitable for farmers to replace the infected tall fescue with an endophyte-free variety.“For dairy and beef cattle farmers, these results are particularly important due to the widespread use of tall fescue and the extensive economic losses associated with animals grazing on tall fescue infected with endophyte fungus,” Marchant said.Tall fescue is a well-adapted pasture grass commonly used for beef production in Kentucky and throughout the United States. However, animals grazing on tall fescue infected with the endophyte fungus often develop physiological disorders that reduce animal performance and, therefore, farm profitability. The U.S. economic loss in beef associated with this endophyte has been estimated at more than $600 million annually, Marchant said.“One solution to this problem has been to replace endophyte-infected tall fescue pastures with endophyte-free varieties,” she said.Marchant and fellow researcher Christopher L. Schardl, along with former graduate students Jun Zhuang, now in a doctoral program at University of Wisconsin-Madison, and Courtney Murrell Butler, with United Foodservice Purchasing Cooperative, conducted a benefit cost analysis to determine the profitability of pasture replacement.

It was based on several assumptions, including percentage of endophyte in existing pastures, stand life, pasture stocking rates and the initial investment of replacement. They also considered economic management strategies and the endophyte effects on animal fertility – factors that had not previously been taken into account.“We have conflicting messages that can be presented to the livestock farmers with respect to whether endophyte is a good thing or a bad thing,” said Schardl, the Harry E. Wheeler Chair in Plant Mycology at UK. “In essence, it is both.”Schardl said he is hopeful this research provides a practical model for farmers not only in Kentucky but throughout the United States who have been unable to adequately measure both the costs and the benefits of tall fescue replacement. “I do feel that we lacked some sort of guidelines previously for the farmers to go by if they are considering whether to simply retain the tall fescue stand that they had or get rid of it and replant with something that does not have endophyte in it,” he said. “There have been a lot of opinions and anecdotes previously. This study sets up a model to allow a much clearer basis for livestock producers to make their decisions as new information becomes available through the research now under way worldwide.”The Agronomy Journal article on the endophyte research can be found online athttp://agron.scijournals.org/content/vol97/issue3/.