A Diet-Related Condition of Livestock

A former professor at Oregon State University, Doctor A. Morrie Craig performed research on livestock diseases. One area of focus for Dr. A. Morrie Craig was tall fescue toxicosis, which can impact the growth and development of animals such as cattle, horses, and sheep.

Tall fescue, a cool-season perennial grass, is adaptable to diverse environments and is the most common pasture grass in the central and eastern United States. Tall fescue toxicosis results from ergot alkaloids such as ergovaline, which the endophyte fungus produces in tall fescue grass.

In livestock, clinical signs typically begin with lameness in one or both of the hind feet and may progress to necrosis in the affected limb. Gangrene also may occur in the tail and ears. An arched back and weight loss are additional signs of the disease.

While the toxic substance associated with fescue lameness is similar to ergot poisoning, the conditions are distinct. Ergotism typically occurs in the late summer when grass seed heads mature, while fescue toxicosis tends to occur in late fall and winter.

Controlling outbreaks of the disease begins with the removal of all infected forage. Other preventive measures include refraining from the use of pastures when the weather is hot and planting legumes to dilute tall fescue pastures.