Endophytes in Perennial Ryegrass and Tall Fescue Straw (Nutrition Update, Volume 11)

The use of turf-type perennial ryegrass and tall fescue in livestock feed can present significant health risks. While endophytes (symbiotic fungi living within plant tissues) enhance stress tolerance and persistence in these grasses, they may also produce toxic alkaloids that are harmful to livestock when infected straw, screenings, or pasture are consumed.

The two primary toxins of concern are:

Ergovaline – associated with tall fescue endophytes, is a vaso-constrictor, it constricts the blood vessels and reduces blood circulation to the outer parts of the animal’s body.

Animals that have consumed a toxic dose of ergovaline will have difficulty regulating body temperature. The constriction of blood flow also can cause "fescue foot". Fescue foot is characterized by gangrene or tissue death in the legs, ears and tails.

Lolitrem B – associated with perennial ryegrass endophytes

result in muscle tremors, muscle weakness and spasms. You may not see any symptoms of toxicity until the animal becomes excited or stressed. When the animal tries to run, trembling to severe un-coordination and falling down may occur.

These compounds can cause disorders such as fescue foot (fescue toxicosis) and ryegrass staggers, affecting cattle, sheep, and horses.

Straw from seed production should be tested for toxin levels before feeding.
Recommendation: Use forage-type tall fescue or perennial ryegrass for hay or pasture.

Safe Feeding Levels of Endophyte Toxins

Based on Oregon State University research

Species	Ergovaline (ppb)	Lolitrem B (ppb)
Horses	300–500	Not determined
Cattle	400–750	1800–2000
Sheep	800–1200	1800–2000

To feed test for ergovaline and lolitrem B, samples can be sent to:

139 Oak Creek Building
Endophyte Service Laboratory
College of Agriculture Sciences
Oregon State University
Corvallis, Oregon 97331 USA

Ph: 541-737-2872
Fax: 541-737-8160