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Fescue Toxicity Pros and Cons – Part I

by Wyoming Livestock Roundup

By Anowar Islam

Tall fescue is a cool-season perennial grass. It is the most important cultivated pasture grass in the U.S. grown on more than 35 million acres. This grass is an important component of the pasture systems in about half of the U.S., especially in the southeastern part. 

Tall fescue was introduced to the U.S. from Europe in the 1800s, however it was not widely planted until late 1930s. Acceptance of this grass started to increase sharply because of its many positive attributes. These included easy establishment, tolerance to environmental stresses, disease and pest resistance, high productivity and quality and long grazing season.

Forage nutritive value or forage quality and productivity of tall fescue are relatively high. These attributes make the grass a potential highly productive and nutritious forage for improved animal performance. 

Unfortunately, this grass can cause serious toxicity problems in livestock resulting in a reputation of poor animal gains and reproduction. Grazing tall fescue could result in abortion, production of dead foals, having foaling difficulties or even reduction or failing of milk production to mares or cows.

Fescue toxicity in cattle

There are three prominent syndromes associated with fescue toxicity. These include fescue foot, bovine fat necrosis and fescue toxicity or summer slump.

The typical syndromes or signs for fescue foot include high respiration rate, vasoconstriction – the decrease in the diameter of blood vessels – tenderness of legs and gangrene. Gangrene can result in loss of hooves and/or portion of ears or tails.

Bovine fat necrosis is characterized by the presence of hard masses of fat in the adipose tissue. This is primarily found in the abdominal cavity. Necrotic fat lesions can be observed in intestinal tract all the way to the rectum.

The signs of fescue toxicity or summer slump include poor animal gains, reduced conception rates, intolerance to heat, failure to shed the winter hair coat and high body temperature. These symptoms are typically visible in warmer areas, but can be evident in all tall fescue growing regions. 

In the northern tall fescue growing areas, it is referred to as summer slump, as it is mostly noticeable in the summer. Fescue toxicity is most common and economically important sign in cattle grazing tall fescue.

I will continue discussion on fescue toxicity in livestock, so please keep an eye on my future writings.

Anowar Islam is a professor and University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or

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