Toxic factors in tall fescue.

Tall fescue ( Festuca arundinacea Schreb .), a well adapted perennial grass grown in the transition zone of the U.S., frequently produces toxic symptoms and(or) reduced animal performance. Specific syndromes associated with tall fescue include fescue foot, summer syndrome and fat necrosis. Summer syndrome is related to high environmental temperatures rather than an increase of toxic compound(s) during the summer months. Recent studies have related the summer syndrome to the presence of an endophytic fungus. The fungus has been identified as Epichlo ë typhina or Acremonium coenophialum Morgan-Jones and Gams by different research groups. Only one fungus is probably involved and it is only the identification that is questioned. The toxic compound(s) involved in fescue toxicity syndromes has not been identified, however, several alkaloids have been associated with depressed animal performance. Other evidence indicates that compounds other than alkaloids may be involved. The depressed prolactin levels associated with fescue toxicosis may provide a technique to aid in the identification of the toxic compound. The development of an enzyme-linked immunosorbant assay for the detection of the fungus should prove an effective tool to identify and thus select fungus free tall fescue seed.