Horse Nutritional Myopathy: Welfare and Prevention

Nutritional myopathy from selenium and vitamin E deficiency causes muscle damage in horses, creating preventable welfare harm particularly in foals.

Key Facts

Nutritional myopathy (white muscle disease) is caused by deficiency of selenium and/or vitamin E
UK soils are often selenium-deficient, particularly in Scotland, the South West and Wales
Foals are most susceptible and can die from cardiac and respiratory muscle damage
Adult horses may show muscle stiffness, weakness and difficulty swallowing in severe cases
Selenium toxicity from over-supplementation is also possible and can cause hair loss and lameness
Blood selenium levels can be tested to identify deficient horses before clinical signs develop
Selenium-rich forages from selenium-adequate soils can meet requirements without supplementation
Vitamin E from fresh grass is rapidly lost in preserved hay and haylage

Welfare Considerations

Nutritional myopathy in foals causes severe suffering and death from muscle breakdown affecting the heart and respiratory muscles. Prevention through appropriate selenium and vitamin E supplementation is straightforward once deficiency is identified. The condition is entirely preventable with appropriate nutritional management yet continues to cause suffering on premises where testing is not performed. Welfare-centred equine management includes routine selenium testing of soil, forage and blood, with supplementation calibrated to avoid both deficiency and toxicity.

What You Can Do

Test your horses' blood selenium levels annually, especially in regions with low-selenium soils
Have forage analysed for selenium content to calibrate supplementation accurately
Seek veterinary advice before supplementing selenium - toxicity risk is real with over-supplementation
Provide vitamin E supplementation when horses are on hay or haylage without access to fresh grass
Contact your vet immediately if a foal shows weakness, difficulty nursing or abnormal breathing