Explanation: Ergotism or Ergot Poisoning

By Kimberly S. Graetz

At the industry-wide meeting on Thursday, May 10, Dr. Steve Jackson, an equine nutrition consultant and owner of Bluegrass Equine Nutrition, and Dr. Jimmy Henning, an extension forage specialist at the University of Kentucky's College of Agriculture, both mentioned that ergot or alkaloid types of toxins were being sought in the testing of pastures. In discussing the situation further with Jackson on May 11, he said that Merck's Veterinary Manual had a good explanation of ergotism in other livestock.

Following is, in part, what Merck's Manual says about ergotism: "A worldwide disease of farm animals that results from continued ingestion of sclerotia of the parasitic fungus Claviceps purpurea, which replaces the grain or seed of rye and other small grains or forage plants, such as the bromes, bluegrasses, and ryegrasses. The hard, black, elongated sclerotia may contain varying quantities of ergot alkaloids of which the levoratatory alkaloids, ergotamine and ergonovine (ergometrine), are pharmacologically most important. Cattle, pigs, sheep, and poultry are involved in sporadic outbreaks, and most species are susceptible.

"Ergot causes vasoconstriction by direct action on the muscles of the arterioles, and repeated dosages injure the vascular endothelium. These actions initially result in reduced blood flow and, eventually, complete stasis with terminal necrosis of the extremities due to thrombosis. (Editor's note: In cattle, for instance, their tails might fall off.) A cold environment predisposes the extremities to gangrene. In addition, ergot has a potent oxytocic action and also causes stimulation of the CNS, followed by depression.

"Cattle may be affected by eating ergotized hay or grain or occasionally by grazing seeded pastures that are infested with ergot. Lameness, the first sign, may appear two to six weeks or more after initial ingestion, depending on the concentration of alkaloids in the ergot and the quantity of ergot in the feed...Body temperature and pulse and respiration are increased."

Merck's Manual goes on to say that ingestion of ergot-infested grains in pigs may result in reduced feed intakes and reduced weight gains. "If fed to pregnant sows, ergotized grains result in lack of udder development with agalactia at parturition and the birth of small litters of weak, undersized piglets of which few survive."

In sheep, signs are similar to cattle, and the mouth may be ulcerated.
"Diagnosis is based on finding the causative fungus in the grains, hay, or pastures. Ergotism can be controlled by an immediate change to an ergot-free diet. Under pasture feeding conditions, frequent grazing or topping of pastures prone to ergot infestation during the summer months reduces flower-head production and helps to control the disease. Grain that contains even small amounts of ergot should not be fed to pregnant or lactating sows."