14. ERGOT

Claviceps purpurea

(fungus)

TOXICITY RATING: Moderate. While ergot itself is extremely dangerous, modern feed production practices are vigilant in not allowing ergot into grain mixtures. Pasture poisoning remains the most likely source for toxicosis.

ANIMALS AFFECTED: Any animal consuming affected grain or grass seed heads: primarily swine, cattle, sheep, and goats. Poultry and horses may also be affected.

DANGEROUS PARTS OF PLANTS: Fungal bodies in the seed heads of grains and grasses.

CLASS OF SIGNS: Behavioral changes, lameness, abortions, convulsions, gangrene, death.

PLANT DESCRIPTION: Ergot (fig. 14) is a fungus parasite of the heads of grasses. In mid- to late-summer, entire grains are replaced by the black, hardened bodies of the fungus. Each body is up to 1 inch long, larger than the normal grain, and protrudes conspicuously from the head. One to a half dozen ergot bodies may develop on one head of grass. Ergots on wheat are straight. On rye they usually are curved. Ergot is found wherever its host plants grow. Rye is the most frequently attacked grain. Other grain, hay, turf, and weedy grasses may be affected, including wheat, oats, wild rice, Kentucky bluegrass, perennial ryegrass, redtop, smooth brome, orchardgrass, quackgrass, reed canarygrass, etc. When grain or hay is harvested, ergot bodies may fall to the ground and be left behind to infect the next season's crop.

SIGNS: The amines and the alkaloids in ergot (ergotamine being one of the major alkaloids) produce a number of clinical signs relating primarily to vasoconstriction and psychoactive effects. The ergot toxins are very similar structurally to lysergic acid (LSD). Wheat and rye contaminated with ergot has affected humans, and the resulting disorder is called St. Anthony's Fire. It is also believed that the one of the reasons for the Salem witch trials was due to the abnormal behavior of persons affected with ergot toxicosis from contaminated rye flour. Ergot has been used in herbal medicine to control hemorrhage during childbirth, and is used currently as a drug to help control migraines.

Animals may be affected by ergot from eating small amounts over a long period of time, or eating greater quantities in a short period of time. Chronic toxicity is more common, with signs manifesting within several weeks of ergot consumption, and field exposure to ergot is more common than processed feed or flour exposure.

The clinical signs can vary, but often begins with swelling of and pain in the extremities, especially the hind legs, due to the constriction of blood vessels. Later, sensation is lost in the affected areas, and dry gangrene can develop. Eventually, the affected areas may slough ("fall off"), with typical losses including claws, hooves, teats, ears, or tail. In addition to the vascular effects, neurologic signs are often seen, such as apprehension, nervousness, and convulsions. Some animals may show signs of depression. Death can occur, but only with significant quantities ingested. In sublethal cases, once the source of ergot is removed, recovery from neurologic signs is likely, but recovery from the vascular effects and gangrene is not likely. Ergot poisoning has been implicated in cases of abortion in large animals.

FIRST AID: Remove animals from the source of ergot, whether in feed or pasture. Call a veterinarian if nervous signs are present. In cases of dry gangrene, the affected portion will be likely to spontaneously amputate. A veterinarian can advise and assist. Always exercise caution when working around animals that have nervous and behavioral changes to prevent human injury.

SAFETY IN PREPARED FEEDS: Ergot remains toxic in feed and should never be fed. Most feed producers are aware of ergot, so it is rare to have it contaminate commercially prepared feeds.

PREVENTION: Screen grains carefully prior to feeding or planting. Affected pastures may produce ergot each year under the right environmental circumstances (typically after wet, cool spring growing seasons). Commercially prepared feeds will not contain ergot. Pasture managers need to be able to identify ergot and limit animal access to affected fields. Keeping the pasture grasses mowed to prevent seed head formation will greatly decrease the presence of the ergot fungus. The fungus is likely to be present in the pasture, so infestations may occur in any year with the right environmental conditions.