An outbreak of Vicia villosa (hairy vetch) poisoning in grazing Aberdeen Angus bulls in Argentina.

Vicia villosa (hairy vetch) is used as a forage source in some cattle-producing areas in Argentina. The plant had no previous reports of toxicity in this country. A herd of 33 Aberdeen Angus bulls grazed during 20 days in October on a pasture composed mainly of hairy vetch. Eight animals developed conjunctivitis, rinitis, dermatitis, loss of hair and fever. All of them died within 15 d after the development of signs with a marked loss of body condition. No more animals became sick 5 d after the removal of the herd from the pasture. Serum parameters tested (calcium, phosphorus, magnesium, GOT, alfa-GT and bilirubin) enlarged liver and spleen, generalized hemorrhage in the abomasum, dilated kidneys and multiple pale areas on the heart. Severe necrotizing granulomatous myocarditis, interstitial nephritis, and necrotizing cholangitis were the most striking microscopic changes. Close observation of animals feeding on pastures in which V villosa is dominant is the only prevention.