Tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] is an introduced cool-season perennial grass from Europe. Originally imported for regularly flooded pastures, tall fescue is now widespread across the United States due to its adaptability of a wide range of soils and climate. Kentucky 31 tall fescue is the ecotype discovered in 1931 by E.N. Fergus, which launched its popularity as a dependable, adaptable, and palatable pasture crop. In the mid-1970s, the negative effects caused by consuming tall fescue were termed fescue toxicosis. The source of fescue toxicosis was not identified until Charles Bacon first reported evidence of an endophytic fungus in tall fescue. The endophytic fungus, later identified as Neotyphodium coenophialum, has a symbiotic relationship with tall fescue. Tall fescue provides nutrients for the endophyte, while Neotyphodium coenophialum produces toxic alkaloids that protect the plant from herbivory, diseases, and gives the plant its tolerance of many environmental stresses, including drought. The three main classes of alkaloids that potentially cause fescue toxicosis are ergot, pyrrolizidine (lolines), and pyrrolopyrazine (peramine) alkaloids (Schultz). Ergot alkaloids are made up of three families: ergopeptines, ergolines, and clavines. Ergovaline, an ergopeptine, is the primary alkaloid toxin affecting grazing mammals. Neotyphodium coenophialum does not change the appearance of the plant. Therefore, the endophyte is only detected by laboratory analysis. Endophyte-infected tall fescue spreads solely by seed. Due to the vast acreage of tall fescue, fescue toxicosis is the top toxicity problem of large animals in the United States
