In regions of low soil selenium, white muscle disease (WMD) is one of the most common causes of acute skeletal and/or heart muscle disease in foals. The disease should be suspected in foals born dead, have signs of muscle stiffness or profound weakness, and abnormal elevation in serum CK and AST activities. The cause is a dietary deficiency of selenium and/or vitamin E in gestating mares. This article discusses the symptoms, diagnosis, treatment, prognosis, and prevention of this disease.

White muscle disease (nutritional myodegeneration) of foals is a peracute to subacute degenertive disease affecting skeletal and cardiac muscle. It is caused by a dietary deficiency of selenium and vitamin E, usually in association with predisposing factors such as a high intake of dietary unsaturated fats or unaccustomed exercise.

White muscle disease has been observed in foals from birth to one year of age, particularly those foals born to dams fed selenium-deficient diets, during gestation. The disease in foals may present as a rapidly fatal disease or a chronic syndrome characterized by profound muscular weakness. Failure of passive transfer, aspiration pneumonia, and stunting are frequent complications.

Common findings are firm painful hind limb, lumbar, and neck muscles with progressive muscular weakness, stiffness, trembling, and recumbency. Pneumonia as a result of immunosuppression from the nutritional deficiency, difficult swallowing (dysphagia) from muscle dysfunction, and the resulting aspiration is a frequent complication. In some foals, dysphagia may be the only initial presenting sign. A rapid, irregular heartbeat, profound weakness, recumbency, and sudden death occur when cardiac muscle is involved.