Tall Fescue (Lolium arundinaceum (Schreb.)) is cool-season perennial grass found in pastures throughout the Eastern US, most commonly in the transition zone. It’s tolerance to extreme temperatures, drought, poor soil fertility, heavy grazing, and pests have made it a reliable forage base for livestock pastures. Released in 1943, ‘KY-31’ tall fescue was quickly adopted by cattle producers and now inhabits an estimated 40 million acres in the US.
Soon after its adoption, cattle producers began to notice a reduction in animal performance and signs that animals were heat stressed following tall fescue consumption. These symptoms were an indication of an animal disorder that would later be called “fescue toxicosis” by scientists and producers. In the late 1970s, it was discovered that the cattle health issues with tall fescue were actually caused by a fungus (Neotyphodium coenophialum) living within some plants, which produced a toxic class of compounds termed ergot alkaloids. We refer to these tall fescue plants that contain this fungus as being endophyte infected (E+) and those that do not as being endophyte free (E-)