Fescue toxicity (fescue foot and summer slump syn-drome) is a non-infectious disease occasionally seen in cattle grazing tall fescue pastures. Fescue foot is more often seen in cold weather in thin cattle grazing stockpiled forage. Although the incidence of fescue foot in a herd can be very high, the total number of cattle affected each year is quite low compared to the numbers of cattle grazing fescue. The outward signs vary in severity, and some animals may suffer reduced performance without showing visible symptoms.
This fact sheet will examine symptoms, possible causes, conditions, which tend to promote fescue foot, and methods to reduce potential for the disease.
Symptoms of Fescue Foot
Toxicity symptoms may occur as early as eight days to as long as eight months after cattle have been placed on fescue pasture. Symptoms vary in severity and include:
• Poor gain.
• Dull appearance.
• Slight to rapid loss of body weight.
• Arched back.
• Partial to complete loss of hair from the end of the tail.
• Dry gangrene of the extremities which can lead to loss of the tail switch, ear tips, and, in severe cases, the feet.
• Eruptions and lesions on the legs.
• Redness of the coronary band (top of hooves).
• Elevated body temperature (up to 106°F).
• Elevated respiratory rates (to over 100/minute). It is likely that only a part of the herd will show symptoms.
However, cattle showing initial signs of fescue foot should be immediately removed from the fescue pasture. Early signs would include lameness in one or both rear feet; rough haircoat; shifting weight from one rear foot to the other; soreness in rear legs, many times the left hind leg; flexing of the pastern joint; and loose stools.
Fescue foot is easy to confuse with other conditions such as foot rot or foot injury. Cattle with severe damage, sloughing hooves or deep lesions should be slaughtered.
Excessive weight loss (emaciation) is common in cattle with severe cases. Cattle on fescue should be observed daily. If possible, observation should be early in the morning before cattle have a chance to walk off minor soreness. A veterinarian should be consulted if toxicity is suspected.
What Causes Fescue Foot?
Researchers thought for many years that an alkaloid produced by the fescue plant itself was the culprit. However, it is now suspected that a fungus living in or on the plant produces the toxin. Several species of fungus capable of causing the disease have been isolated, and researchers have speculated that the fungi produce detrimental metabolites, possibly in the rumen.
Managing Pastures and Cattle to Prevent Fescue Toxicity
Whatever the chemical cause, fescue foot seems to occur most frequently under certain circumstances:
• Pure stands of fescue. Forage stockpiled for a season is more likely to be toxic than new regrowth of closely grazed or mowed pastures. Forage accumulated for more than one year is even more likely to be toxic. Fescue stockpiled after mid-summer may be less dangerous than fescue accumulated from the previous spring.
• Fescue baled when toxic will remain toxic.
• Fescue hay of high quality that was baled during the early dough to boot stage is likely to be safe. Hay cut in fall may be dangerous. A pasture that produces fescue foot one year may not be toxic in subsequent years.
• Thin cattle are more easily affected than cattle in good flesh.
• Cattle fed one to two pounds of supplement while on fescue are less susceptible than unsupplemented cattle. Energy may be more important than protein.
• The first lameness often appears after the first cold “spell” and during snow or ice cover.
• Mixtures of fescue with clover, ryegrass, or warm season grasses -such as bermuda are less prone to cause fescue foot than are pure stands of fescue.
• Heavy nitrogen fertilization (over 200 pounds of actual nitrogen per acre each year) may increase the chances of toxicity. Reports of greater incidences of toxicity in fescue that was drought-stressed in summer and fall may be related to nitrogen built up in the soil since slow growing forage will not use up the soil nitrogen.
•Feeding some good quality (non-toxic) hay to cattle grazing fescue pasture may reduce the chances for toxicity by diluting the amount of toxic fescue consumed.
• The toxic condition is thought to be carried in the seed. Researchers report that seed which is at least one year old does not contain live fungus. So one should try to plant seed with good germination that is at least one year old.
Scientists will probably find a way to remove the toxic factor or factors from fescue. However, until that is accomplished, cattlemen will have to rely on good forage management, proper cattle nutrition, and careful detection of early symptoms of fescue foot. Fescue fills a critical gap in winter forage production in eastern Oklahoma. Properly managed it is an excellent forage for stockers and cows.
Source: Glenn Selk / Kent Barnes, Oklahoma State University