Ergot Alkaloids in Ensiled Tall Fescue.

Ergot alkaloids in tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] are produced by the fungal endophyte, Neotyphodium coenophialum. When consumed by livestock, these alkaloids cause a disorder known as fescue toxicosis. In order to lessen the severity of fescue toxicosis, ergot alkaloids concentrations should be reduced in plants, pastures, and ultimately the diet. The objective of this study was to determine if ergovaline (EV) and total ergot alkaloids (TEA) concentrations in tall fescue could be altered by ensiling, and if so, if the magnitude of change could be affected by low and high moisture levels. Neotyphodium-infected tall fescue at Mt. Vernon and Linnues, MO was fertilized with 80 kg N ha^-1 in early April 2007. In late spring, tall fescue was clipped, wilted, baled and wrapped at low and high moisture levels then allowed to ensile for 4 mo. Silage was sampled in September and samples analyzed for EV and TEA by NIR spectroscopy. At Mt. Vernon, ensiling decreased EV approximately 200 µg kg^-1DM, which represented a 24 percent decrease; ensiling increased TEA by approximately 300 µg kg^-1DM, a 33 percent increase. Also at Mt. Vernon, moisture level did not affect on EV concentration but did affect TEA concentration. Low moisture silage contained 448 µg TEA kg^-1DM, and high moisture silage contained 673 µg TEA kg^-1DM. At Linneus, there was a moisture x ensiling interaction. EV concentration decreased in silage of both low and high moisture levels. TEA concentration did not change when grass was ensiled at low moisture but increased when ensiled at high moisture. These study shows that both the ensiling process and the moisture level of silage can significantly alter concentrations of EV and TEA. It is important that future work in toxicology resolve which, EV or TEA, best represents changes in animal performance.