Tetany associated with magnesium deficiency in suckling beef calves.

Sudden death losses occurred in 4-month-old beef calves with clinical signs of muscular dysfunction, including tetanic spasms. Gross lesions were not diagnostic. Microscopic lesions consisted of deposition of calcium salts in the elastic fibers of the arteries in the heart, lungs, and spleen and in the trabeculae of the spleen. Focal areas of interstitial nephritis were characterized by infiltration of lymphocytes and plasma cells. Samples of hay and silage that the cattle were consuming were low in magnesium. Calves with spasms responded to magnesium salts given intravenously, and losses ceased after a magnesium-containing supplement was fed free choice to the calves and cows.