Impact of consuming tall fescue leaves with the endophytic fungus, Acremonium coenophialum, on meadow voles

Most of the 14 million hectares of pastures of tall fescue (Festuca arundinacea) planted in the United States are infected with the endophytic fungus, Acremonium coenophialum. I examined if grazing infected plants had an adverse impact on meadow voles (Microtus pennsylvanicus). Captive voles fed leaves from infected fescue plants (fungus-fed voles) gave birth and weaned as many offspring as voles fed leaves from uninfected plants of the same genotype of tall fescue (control voles). Mass and body temperatures of fungus-fed and control voles did not differ. When maintained at 21 degrees C, mortality rates were similar, but when ambient temperatures were increased to 31 degrees C, fungus-fed voles had significantly higher mortality rates than control voles. Naive voles did not discriminate between infected and uninfected leaves, but after a diet of fescue, voles preferred uninfected leaves.