Endophytes in Perennial Ryegrass and Tall Fescue Straw

Interest in using grass seed production residues as a part of cattle rations has been increasing in recent times in Manitoba. In other areas where turf-type perennial ryegrass and tall fescue residues have been fed, livestock disorders have been observed. These disorders, commonly called fescue foot or ryegrass staggers, have been attributed to fungal organisms called endophytes that live within the grass plant.

Endophyte is a fungus that lives symbiotically within the grass plant and produces toxins that confer disease and insect resistance to the grass. These traits are beneficial for turf-type fescues and ryegrasses which will be grown in areas where insect and disease pressure can damage turf stands. However, these toxins have also been linked with health disorders in livestock. For this reason, caution should be exercised if turf-type tall fescue or perennial ryegrass residues are to be used in rations for ruminants and horses.

Endophyte fungi are transmitted only by seed and its entire life cycle takes place inside the plant tissues. An individual plant will not become infected by neighboring plants. Different species of endophyte infect tall fescue and perennial ryegrass, producing different toxins. Acremonium coenophialum infects tall fescue, producing ergovaline as the major toxin. Ergovaline is concentrated in the reproductive parts of the grass plant, especially in the seed heads and seed screenings. Toxicity will not be reduced by pelleting the screenings. Acremonium lolii infects perennial ryegrass, and the major toxin produced is Lolitrem B. Ergovaline is typically only a problem in tall fescue and Lolitrem B is typically only a problem in perennial ryegrass.

Each type of endophyte produces different clinical symptoms. The symptoms of ergovaline poisoning in livestock include hyperthermia (elevated body temperature), lower feed intake, weight loss, lower pregnancy rates and decreased milk production. Horses are particularly sensitive to ergovaline and are prone to developing reproductive problems including abortions, difficult births and foal deaths. Fescue foot is also associated with ergovaline and is most apparent in winter months. Animals with this condition will develop swelling in the legs and restricted blood flow to the feet, causing tissue to die and hooves to detach from the feet.

Ryegrass staggers is caused by the toxin Lolitrem B. This condition can result in animals experiencing problems that range from tremors to severe unco-ordination and falling down. This condition requires a seven- to 14-day exposure period and clinical signs usually disappear in two to three days if animals are removed from toxin containing feed.

Table 1. Threshold levels of ergovaline and Lolitrem B in the diet that produce clinical disease.

Ergovaline parts per billion (ppb) Lolitrem B parts per billion (ppb)
Horses 300 – 500 not determined
Cattle 400 – 750 1800 – 2000
Sheep 800 – 1200 1800 – 2000
Recommendations developed by Oregon State University, College of Veterinary Medicine (Aldrich-Markham and Pirelli, 1995)

The recommended maximum restrictions were confirmed from work by Goetsch et. al. This 1987 study showed that endophyte infected straw decreased forage intake, but could be offset by supplementing with alternate noninfected sources of forage. This study used clover and wheat straw as sources of non-infected forage. Later work (Stamm et. al., 1994) where properly supplemented low quality straws containing up to 475 ppb ergovaline were fed to steers, showed no deleterious effects on animal health, nutrition, or performance.

Testing for Endophytes

Endophyte levels can vary between varieties, between fields of the same variety, and with the time of year, so the only way to be certain of toxin levels is to have the straw tested. Perennial ryegrass and tall fescue can be tested for ergovaline and Lolitrem B contents by sending samples to:

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

Phone: 541-737-2872
Fax: 541-737-8160

The costs of the tests are $40.00 USD each for the ergovaline test, which takes three to four weeks, and the Lolitrem B test, which takes two to three weeks. The samples can be sent by Canada Post or Purolator. Currently there is no permit or prior notice form required to send these samples; however, they are subject to inspection at the border so clearly label the envelope "Perennial Ryegrass Straw" or "Tall Fescue Straw."

Randomly collected samples can be made by collecting core samples from at least 20 bales. It is important that samples are air dried to avoid spoilage and are kept out of direct sunlight. Samples that are sealed in plastic freezer bags can be sent to the above address with appropriate contact information and payment. For further details phone the Oregon State University testing lab at 541-737-2872.

Table 2. Ergovaline levels for straw, straw/chaff and chaff samples of tall fescue seed production in the central region of Manitoba in 2000.

Tall Fescue Ergovaline levels (ppb)
Straw Straw/Chaff Chaff
<10 10 15
<10 <10 18

Table 3. Lolitrem B levels for straw, straw and chaff, and chaff samples of perennial ryegrass seed production in the Central Region of Manitoba in 2000.

Perennial Ryegrass Lolitrem B levels (ppb)
Straw Straw and Chaff Chaff
2418 3276 2882
4888 6650 4908

Endophyte levels are high enough in some of these samples to warrant mixing of non- endophyte containing feeds.

Feeding Recommendations

  1. Seed forage-type varieties of tall fescue and perennial ryegrass, with low or no endophytes, if seed production residues are to be used as animal feed.
  2. Since toxins are concentrated in the seeds, screenings from perennial ryegrass and tall fescue should never be fed to livestock.
  3. Test turf-type tall fescue and perennial ryegrass straw for ergovaline and Lolitrem B levels to determine the risk potential.
  4. Do not feed infected plants to pregnant or lactating animals. Pregnant mares are particularly at risk.
  5. Mix non-endophyte containing forages with endophyte infected straw to reduce toxin levels in the total ration. Tub grinding and limited feeding of the infected forage are two options to consider.
  6. Animals fed a poor diet are more susceptible to toxicity. Ensure rations are properly balanced for energy, protein, minerals and vitamins.
  7. The threshold levels for ergovaline and Lolitrem B, shown in this factsheet, can be affected by stress and environment. All animals fed endophyte-containing forages should be watched closely and the contaminated feed removed immediately if toxic symptoms are observed.
  8. Ammoniation of the straw has been shown to reduce toxicity.
  9. Use a chaff spreader to reduce the chaff content of straw since the endophyte content of chaff is usually higher than straw.


Aldrich-Markham, S. and Pirelli, G. 1995. Endophyte Toxins in Grass Seed Fields and Straw – Effects on Livestock. Oregon State University Extension Service Publication.

Goetsch, A.L.; Jones, A.L.; Stokes, S.R.; Beers, K.W.; Piper, E.L. 1987. Intake, digestion, passage rate and serum prolactin, in growing dairy steers fed endophyte-infected fescue with non-infected fescue, clover, or wheat straw. J. Anim. Sci. 64:1759-1768.

Stamm, M.M.; DelCurto, T.; Horney, M.R.; Brandyberry, S.D.; Barton, R.K. 1994. Influence of tall fescue straw on the nutrition, physiology, and subsequent performance of beef steers. J. Anim. Sci. 72:1068 –1075.