Alleviation and mitigation of fescue toxicosis

Abstract Text:

Tall fescue (Lolium arundinaceum L.) is a cool-season perennial grass that is utilized as a forage on approximately 16 million hectares of the USA, primarily in the transition zone between the temperate northeast and subtropical southeast.  A fungal endophyte (Epicloë coenophialia) that infects most plants of the most widely grown cultivar, Kentucky 31, produces alkaloids that impart the plant with tolerances to environmental stresses, but also produces ergot alkaloids that causes a toxicosis.  The signs of “fescue toxicosis” include maintaining rough hair coats during the summer, elevated body temperature, labored respiration, and decreased prolactin concentrations.  Ergot alkaloids bind alpha adrenergic receptors in peripheral vasculature of ruminants that disrupts thermoregulation and makes them vulnerable to severe heat stress at onset of moderate air temperatures.  Calf weight gain can be very low on toxic tall fescue, which has limited the use of fescue for stocker production.  Although the grass is primarily used for cow-calf production, calving percentages, milk yields, and weaning weights can be reduced on toxic endophyte-infected tall fescue.  Non-toxic endophyte tall fescues have been commercially released that demonstrate to alleviate fescue toxicosis.  Other technologies, such as chemical seedhead suppression, feeding soy hulls, and overseeding with red clover also have shown to mitigate fescue toxicosis.  Evaluations of the efficacy of these new technologies in enhancing cattle performance and well-being on toxic endophyte-infected tall fescue will be presented and discussed. 

Keywords: endophytes,Epicloë coenophialia, fescue toxicosis, Lolium arundinaceum, tall fescue