Perennial Ryegrass: Endophyte Feeding Concerns

There have been reports of high levels of endophytes in perennial ryegrass this fall. Endophytes are fungal growths that are mainly found in ‘turf-type’ tall fescue and perennial ryegrass varieties. Endophytes (endo = inside, phyte = plant) produce toxins that are harmful to livestock if consumed in high enough concentrations. Ergovaline is the main toxin found in infected tall fescue and lolitrem B is the main toxin found in infected perennial ryegrass.

The toxin ergovaline 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. Animals can become lame, the tips of tails and ears may fall off or the sloughing of hooves can occur. This can look similar to the disease commonly called “ergotism” with similar toxins produced by another fungus species Claviceps which can occur in small grains and forage plants such as bromes, bluegrasses, and ryegrasses.

Ryegrass staggers, is caused by the toxin lolitrem B, which can 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 uncoordination and falling down may occur. Livestock would need to be fed infected perennial ryegrass for seven to fourteen days for symptoms to occur. The signs would disappear two to three days after the feed was removed, although they may last as long as two weeks.

The threshold levels of ergovaline that can be included in beef cattle rations is 400 to 750 parts per billion (ppb) and 1800 to 2000 ppb for lolitrem B toxin. Since the toxin level within endophyte-infected forage is highly variable, feed testing is the best way to decide how the feed should be used. Once the endophyte levels are known, endophyte-free feed can be mixed to dilute the toxin to a safe level.

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