EFFECTS ON SHEEP OF THE MILKWEEDS ASCLEPIAS-ERIOCARPA AND ASCLEPIAS-LABRIFORMIS AND OF CARDIAC GLYCOSIDE-CONTAINING DERIVATIVE MATERIAL

J. M. Benson, J. N. Seiber, C. V. Bagley, R. F. Keeler, A. E. Johnson and S. Young. Effects on sheep of the milkweeds Asclepias eriocarpa and A. labriformis and of cardiac glycoside-containing derivative material. Toxicon 17, 155-165, 1979.-Some milkweeds native to the western United States are extremely toxic to range animals. As little as 0·05 and 0·25% of an animal's weight of Asclepias labriformis and Asclepias eriocarpa, respectively, may be lethal (Kingsbury, 1964). Cardiac glycosides (cardenolides) in these species have been implicated as toxic principles. In experiments conducted to verify this toxicity, four preparations were tested on sheep: dried, ground A. labriformis and A. eriocarpa plants, a crude ethanolic A. eriocarpa extract, and a partially purified extract from which pigments and fats had been removed. In addition, labriformin (a purified cardenolide present in A. labriformis and A. eriocarpa), and digitoxin (a clinically important cardenolide) were administered. Toxic symptoms and gross and histopathological lesions were qualitatively similar regardless of whether plants, extracts, labriformin or digitoxin were administered. Results of these experiments strongly suggest that cardenolides found in A. labriformis and A. eriocarpa account for the effects of these plants on sheep. © 1979.