Ministry of Agriculture
Tall Fescue and Endophytes
- What is Endophyte?
- Disease Symptoms in Livestock
- Avoiding Endophyte Toxins
Two articles appeared in The Western Producer in September 1999 that may be causing concern and confusion for livestock producers who grow and feed tall fescue. The first, entitled "Tall fescue deadly for some Alberta cattle" ran in the Sept. 2, 1999 issue. It told of several Peace River producers who had to shoot cattle that lost feet or went lame after eating tall fescue seed screenings and hay (presumably the aftermath from seed fields). What the article failed to point out was that there are two distinct types of tall fescue - turf and forage. In recent years, seed production of turf-type tall fescue has increased in the Peace and it is the screenings and aftermath from this crop that have caused the livestock problems.
The second article appeared in the Sept. 23, 1999 issue and was entitled "Lawn-type fescue not suited for pasture". It quotes Todd Hyra, manager of crop development with Proven Seed, as saying that farmers need to make sure they don't buy turf-type tall fescue for hay or silage production.
What is the difference between these two types of fescue? The following information, taken from an Oregon State University Extension Service factsheet, addresses this issue.
"Both grass seed growers and livestock producers can benefit by grazing animals on grass seed fields and feeding grass seed straw. However, problems can develop if livestock consume turf varieties of tall fescue and perennial ryegrass. Some turf varieties are infected with high levels of endophyte, which produces toxins harmful to livestock.
Endophyte is a fungus that lives inside the grass plant. The relationship between grass and endophyte is symbiotic, that is, they both benefit. Although endophyte does not harm grass, it produces toxins that are harmful to livestock. Since it does not affect the appearance of the grass plant, its presence can be detected only by laboratory analysis.
Some grass varieties grown for turf seed have high levels of endophyte. The reason is that infected plants can have increased growth, increased drought tolerance, and resistance to certain insects - qualities for which plant breeders select.
All of the forage varieties of tall fescue and perennial ryegrass produced in Oregon, however, are endophyte-free or have very low levels of endophyte. Breeders of forage varieties have been selecting out infected fields since the 1970s, when the connection between endophyte in tall fescue and a livestock disease called fescue toxicity was discovered.
Endophyte is transmitted only by seed, and its entire life cycle takes place inside plant tissues. A plant does not become infected from its neighbours. Therefore, a stand of a non-infected variety will remain non-infected. If it is over-seeded with an infected variety, only the new plants will be infected. A stand of an infected variety cannot be cured with an application of fungicide.
Tall Fescue Toxicity is caused by the toxin ergovaline. The effects on livestock include hyperthermia (elevated body temperature), lower feed intake and weight loss, lower pregnancy rates, and decreased milk production. These clinical signs, although more apparent during hot weather, can occur at anytime of the year. Horses are especially prone to developing serious reproductive problems - abortions, difficult births, and foal deaths.
Another disease condition, fescue foot, is more apparent in the winter. Animals with this condition have swelling in the legs and restricted blood flow to the feet, which causes tissue to die and hooves to detach from the feet. Tissue death because of restricted blood flow also can occur at the tip of the tail and ears.
Fields planted with certified seed of zero- or low-endophyte forage varieties of tall fescue or ryegrass should be safe to graze or cut for hay. To keep them endophyte-free, livestock producers should not over-seed with infected turf varieties.
Ergovaline, the toxin produced by the tall fescue endophyte, is concentrated in the reproductive parts of the grass plant, especially the seedheads (and seed screenings). Toxicity is not reduced by pelleting the screenings. Therefore, feeding seed screenings from unknown grass seed fields is risky.
In both tall fescue and perennial ryegrass, the endophyte fungus loses viability in seed that is stored 18 months or more, especially if it is stored at high temperature and high moisture levels. The percent of infection in old seed and in plants grown from old seed is reduced.
Ergovaline, however, is still present after several years of storage. Storing infected grass seed straw or screenings doesn't make them safer to feed. Also, making silage does not reduce toxicity, although ammoniating straw does.
Ergovaline levels may vary among different fields of the same grass variety with the same level of endophyte infection. Also, ergovaline levels in the same field may vary at different times of the year and in different years.
New leaf growth in the fall following seed harvest has more ergovaline than leaves at other times of the year. Increased nitrogen fertilization can increase the ergovaline level. Therefore, testing for the toxin is the best way to decide how (or whether) a feedstuff should be used in a livestock diet.
Oregon State University can test straw, seed screenings, or pasture grass for ergovaline. The cost is US$35 per sample.
It is important to take a representative sample. To sample straw, take core samples from at least 20 randomly selected bales in a lot. To sample a pasture, take grass plants from at least 20 locations. Air dry the grass, not in direct sunlight.
Seal samples in a polyethylene freezer bag and label them with your name, phone number, and a sample identification. Send them, along with your payment, to the address below:
Veterinary Diagnostic Laboratory
PO Box 429
Corvallis OR 97339 USA
Tel. (541) 737-6541
In summary, livestock producers in the Peace should avoid feeding seed screenings and forage aftermath from turf-type tall fescue fields. All livestock producers in the province growing or thinking of growing tall fescue for forage should plant only a zero- or low-endophyte forage-type variety. Currently, such varieties being sold in BC include Atlas, AU Triumph, Barcel, Courtenay, Dovey, Festorina, Fuego, Maximize, Montebello, Seine and Stef. Finally, dairy producers at the coast have been growing and feeding forage-type tall fescues for over ten years with no livestock problems.