Ergotism and fescue toxicosis are clinically similar syndromes caused by consuming plants containing ergot alkaloids. The toxic effects and mechanisms of action are similar in both syndromes although the alkaloids are produced by different species of fungi. Ergot is a fungus that grows on the seed head of cereal grains and grasses. The term “ergot” is used in general as a common name for the Claviceps fungi or it may be used more specifically when referring to the ergot body of Claviceps purpurea when present on rye. These fungi parasitize the ovary of the developing grass flower and prevent development of the seed by sending fungal filaments throughout the tissue. From the tips of these fungal filaments, spores are formed and shed in drops of a sticky sweet matrix known as “honeydew.” Insects feed on the sticky droplets and spread fungal spores to additional grass heads. The filaments ultimately harden into structures which replace the grain or grass seed. This new, hard structure is called a “sclerotium” or “ergot body” and is the poisonous stage of the Claviceps life cycle for livestock. The ergot bodies are either harvested with the seed head or drop off and overwinter in the field to produce spores the following spring. Claviceps purpurea grows on rye, wheat, barley, triticale, oats, and various grasses. Rye and triticale are more susceptible than other grains because they require a longer period of pollination. Grasses potentially infected include tall fescue, bluegrass, brome, canarygrass, quackgrass, timothy, wild barley, and annual and perennial ryegrass. Shallow cultivation, no-till farming, and lack of crop rotation increase the likelihood of infection of crops. Environmental conditions of a cool, wet spring followed by hot early summer temperatures are ideal for the fungus to grow.

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This is part of the Forage-Related Cattle Disorders series.