Environmental zinc and cadmium pollution associated with generalized osteochondrosis, osteoporosis, and nephrocalcinosis in horses.

Several suspect causes of chronic zinc/cadmium toxicosis in horses near a zinc smelter were investigated following observations of lameness, swollen joints, and unthriftiness, particularly in foals. Two foals born and raised near the smelter were lame and had joint swellings that were attributable to severe generalized osteochondrosis. Zinc and cadmium concentrations were markedly increased in the pancreas, liver, and kidney. The serum of 1 foal, zinc and potassium concentrations were high, whereas calcium and magnesium concentrations were low. Marked nephrocalcinosis and osteoporosis were observed in this foal. Nephrocalcinosis also was observed in his dam, who died of a punctured lung following rib fractures, though there was no history of trauma. The joint cartilage lesions were similar to those induced experimentally in animals fed high-zinc diets and may have been the result of zin-induced abnormality of copper metabolism. The osteoporosis and nephrocalcinosis were consistent with chronic cadmium toxicosis.