Nutritional myopathy associated with selenium and copper deficiency in beef cattle in Argentina.

Nutritional myopathy (NM) is a sporadic disease of growing cattle, mostly associated with selenium (Se) deficiency, and characterized by necrosis of striated muscle. There is scant literature about NM in adult cattle. We describe 2 clusters of gastrocnemius and serratus ventralis NM associated with Se and copper (Cu) deficiency in adult beef cattle in Argentina. Cluster 1 included bilateral dropped hocks in 5 cows. Grossly, the gastrocnemius muscles of both hindlimbs had symmetrical hemorrhagic foci surrounded by pale-yellow areas. Cluster 2 included bilateral dorsal scapular displacement in a cow and a heifer. The animals of cluster 2 had diffusely elongated and pale-white serratus ventralis muscles. Microscopically, the affected muscles of all of the animals in the 2 clusters had polyphasic degeneration and necrosis. We observed below-normal blood glutathione peroxidase activity and plasma Cu concentrations in affected and unaffected animals of both clusters. Liver and kidney Se concentrations were normal, likely because the animals had been supplemented with this mineral soon before death. Liver Cu was below the normal range in all autopsied animals. Cu deficiency could favor oxidative damage produced by Se deficiency and interfere with collagen synthesis in the epimysium, predisposing the animal to muscle injuries. Although NM is more frequent in growing cattle, it should also be considered among the differential diagnoses for lameness in adult cattle.