Seasonal Fluctuation of Ergovaline and Total Ergot Alkaloid Concentrations in Tall Fescue Regrowth

摘要

Common cultivars of tall fescue [Schedonorus arundinaceus (Schreb.) Dumort = Lolium arundinaceum (Schreb.) Darbysh.] host a fungal endophyte that produces ergot alkaloids. These alkaloids are linked to fescue toxicosis, a serious livestock disorder in the United States. This study was conducted to determine how ergot alkaloid concentrations fluctuate throughout the growing season in tall fescue regrowth. In 2005, plots were established in pastures of endophyte-infected tall fescue growing in Missouri, Georgia, and South Carolina. Each month of the growing season, plots were clipped and forage allowed to regrow; regrowth was sampled from April through October 2006 and analyzed for ergovaline and total ergot alkaloid concentrations. At all three sites, ergovaline concentration was lowest during the spring, increasing slightly through the summer months and then sharply in the early autumn. This pattern of ergovaline fluctuation did not mimic data published from experiments in which tall fescue was grazed or was allowed to grow without defoliation. Total ergot alkaloid concentration followed a bimodal curve, with highest concentration in the spring and fall and lowest concentration in the summer. We conclude that common cultivars of endophyte-infected tall fescue should be regarded as highly toxic in the autumn and less toxic in the summer, even if pastures are clipped. We also conclude that the toxicity potential of tall fescue regrowth in the spring depends on which ergot alkaloids prove most responsible for fescue toxicosis.