Horse Nutritional Myodegeneration and Vitamin E

Vitamin E and selenium deficiencies cause serious muscle disease in horses, with particular risks for foals and horses on certain diets.

Key Facts

Nutritional myodegeneration (white muscle disease) results from selenium and/or vitamin E deficiency
It primarily affects foals but can occur in adult horses, particularly those on hay-only diets
Selenium-deficient pastures are common in many parts of the UK, Europe, North America, and Australasia
Clinical signs include muscle stiffness, reluctance to move, difficulty suckling in foals, and myoglobinuria
Treatment involves selenium and vitamin E supplementation; severe cases require supportive care
Routine supplementation of mares in deficient areas prevents foal disease effectively

Welfare Considerations

Nutritional myodegeneration causes severe muscle pain equivalent to whole-body cramping. Affected foals cannot suckle effectively, may become recumbent, and suffer from profound weakness and pain. The condition is entirely preventable through appropriate maternal supplementation during pregnancy in selenium-deficient areas. Adult horses on restricted diets or in selenium-poor areas may develop milder but still welfare-significant muscle disease causing stiffness, poor performance, and pain. Regional soil selenium maps allow targeted supplementation programs that prevent deficiency disease. Veterinary guidance is essential as selenium has a narrow therapeutic window - over-supplementation causes toxicity that is as serious as deficiency.

What You Can Do

Consult your veterinarian about selenium status in your region and whether supplementation is indicated
Supplement broodmares with selenium and vitamin E in selenium-deficient areas before and during pregnancy
Do not supplement with selenium without veterinary guidance - toxicity is as dangerous as deficiency
Provide access to quality hay and appropriate vitamin E supplementation for horses on hay-only diets
Recognize white muscle disease signs in foals: weakness, stiffness, reluctance to nurse - seek vet care promptly
Test blood selenium levels in horses in high-risk areas to guide targeted supplementation