Field Studies on Etiology and Control of Fescue Toxicosis 1

An outbreak of fescue toxicosis occurred in cattle in the southern part of Mississippi in 1969–70. A survey of veterinarians and county agents revealed that fescue toxicosis occurred in 15 Mississippi counties, with general distribution across the state. Field investigations were conducted to gain additional information on the role of fungi in the etiology of fescue toxicosis and to determine if an antifungal agent would be beneficial in controlling the disease. Thiabendazole [2-(4-Thiazolyl)-benzimidazole], a drug with known anthelmintic and antifungal properties, was found to be of benefit in preventing symptoms of fescue toxicosis when administered periodically to cattle before and during grazing on known toxic fescue pastures. Thiabendazole was effective when administered orally immediately before the animals were put on toxic fescue and at 7-day intervals at a dosage of 5.0 g/45.5 kg body weight, but it was not effective at a dosage of 1.0 g/45.5 kg body weight administered in the same way. The symptoms of fescue toxicosis occurred more often after or during rainy, overcast weather.