Interest in using grass seed production residues in cattle rations has been increasing in Manitoba. In other areas where turf-type perennial ryegrass and tall fescue residues have been fed, livestock disorders have been observed, according to Glenn Friesen, a forage specialist with Manitoba Agriculture.
These disorders, commonly called fescue foot or ryegrass staggers, have been attributed to fungal organisms called endophytes that live within the grass plant.
An 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 where insect and disease pressure can damage stands.
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However, these toxins have also been linked with health disorders in livestock. Caution should be exercised if turf-type tall fescue or perennial ryegrass residues are used in rations for ruminants and horses.
Endophyte fungi are transmitted only by seed and the entire life cycle takes place inside the plant tissues. An individual plant will not become infected by neighbouring plants.
Different species of endophytes 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.
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 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 hoofs to detach.
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 feed containing the toxin.
A study showed that endophyte-infected straw decreased forage intake, but could be offset by supplementing with alternate non-infected sources of forage.
This study used clover and wheat straw as sources of non-infected forage.
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 the Endophyte Service Laboratory at the College of Agricultural Sciences at Oregon State University in Corvallis, Oregon.
The costs of the tests are $40 US 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. 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 kept out of direct sunlight.
