Nutritional Myodegeneration
Learn what the condition is, how it may be detected early, how it is treated or managed, and which breeds or species are linked to it.
Condition snapshot
A concise guide to the condition’s pattern, detection, management and urgency.
This snapshot is a general guide, not a diagnosis or treatment plan. New, severe or worsening signs require veterinary assessment.
About the condition
Nutritional myodegeneration is oxidative damage and necrosis of skeletal or cardiac muscle associated principally with inadequate selenium and vitamin E. It most often affects rapidly growing foals whose dams consumed selenium-deficient diets during late pregnancy. Selenium and vitamin E support complementary antioxidant systems that protect cell membranes from normal metabolic free radicals.
Skeletal-muscle disease causes weakness, stiffness, trembling, firm painful muscles, difficulty rising, poor suckling and trouble chewing or swallowing. Damaged muscle can release myoglobin, turning urine dark. Aspiration pneumonia is common when swallowing fails. Cardiac involvement produces rapid or irregular heartbeats, breathing difficulty, collapse and sudden death, sometimes before marked limb signs are recognised. Adult horses can rarely develop selenium-associated masseter muscle disease or non-exertional rhabdomyolysis.
The condition is sometimes called white muscle disease because affected tissue can appear pale, but this gross description is neither an ante-mortem test nor unique to nutrient deficiency. Infectious disease, botulism, congenital heart disease, electrolyte disturbance and other myopathies can resemble it. A deficient pasture or dam does not prove the foal’s weakness has this cause.
Geographic soil selenium varies dramatically, and commercial feeds may already be fortified. Blind supplementation is hazardous because the safety margin for selenium is narrow; excess can cause acute death or chronic mane, tail and hoof damage. Prevention therefore requires analysis of the complete ration and regional veterinary advice. Prognosis is reasonable for skeletal disease treated before severe aspiration, but guarded to poor when cardiac muscle is substantially affected.
Vitamin E and selenium protect muscle membranes from oxidative injury. Deficiency can produce weak, recumbent foals, dysphagia, respiratory compromise or sudden death, while adults may show stiffness and poor performance. Selenium has a narrow safety margin, so supplementation without measuring the whole ration can replace deficiency with potentially fatal toxicity.
Screening & Early Detection
A weak, stiff or dysphagic foal receives urgent examination of heart rhythm, breathing, swallowing and ability to stand. Serum CK and AST document muscle injury; CK rises rapidly, while AST can remain elevated longer. Electrolytes, kidney values, urinalysis and cardiac troponin or ECG help grade systemic and myocardial involvement.
Whole-blood selenium and plasma or serum alpha-tocopherol are measured with appropriate sample handling. Selenium-dependent glutathione peroxidase reflects longer-term status because it is incorporated during red-cell production. Both foal and dam may be tested, and the mare’s complete diet, pasture, hay and fortified feeds are audited. Tissue analysis can confirm disease after death.
Low vitamin E or selenium alone must be connected to compatible muscle damage; several neonatal infections and neuromuscular diseases produce weakness. Swallowing assessment and thoracic imaging identify aspiration pneumonia. On a property with one case, other late-pregnant mares and foals should have rations reviewed and, where indicated, measured rather than receiving an uncalculated group injection.
Urine and kidney values are checked when extensive muscle injury could release nephrotoxic myoglobin.
Treatment & Management
Veterinary treatment replaces selenium and vitamin E at a carefully calculated dose and route. Injectable selenium can correct deficiency quickly but overdose may be fatal, so product concentration and the selenium already supplied by feed must be checked. Vitamin E formulation affects absorption, and repeated supplementation is guided by blood values and clinical response.
Supportive care is intensive for weak foals. Fluids and electrolytes maintain circulation, while nutritional support is provided through a safe route when suckling or swallowing is impaired. Oxygen may be needed for respiratory or cardiac involvement. Aspiration pneumonia receives appropriate antimicrobials and airway care. Recumbent foals require deep bedding, regular repositioning and assistance to stand without exhausting damaged muscle.
The dam’s ration and the entire property programme are corrected with a veterinarian or equine nutritionist. Forage and soil region, commercial feed labels, salt and all supplements are included to prevent both deficiency and toxicity. Pregnant mares need adequate intake before foaling because treating the neonate after damage has occurred is less effective. Recovery is monitored with CK, selenium, vitamin E, heart rhythm, swallowing and strength. Sudden arrhythmia, progressive respiratory failure or inability to protect the airway carries a grave prognosis.
Breeds or species affected
Akhal-Teke
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Anglo-Arabian
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Arabian
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Barb
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Caspian
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Kathiawari
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Marwari
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Shagya Arabian
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Thoroughbred
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American Quarter Horse
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American Paint Horse
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Appaloosa
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Australian Stock Horse
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Brumby
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Waler
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Morgan
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Standardbred
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American Saddlebred
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Tennessee Walking Horse
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Missouri Fox Trotter
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Rocky Mountain Horse
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Peruvian Paso
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Criollo
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Mustang
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Canadian Horse
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Andalusian
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Lusitano
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Lipizzaner
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Friesian
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Dutch Warmblood
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Hanoverian
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Holsteiner
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Oldenburg
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Westphalian
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Trakehner
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Selle Français
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Belgian Warmblood
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Danish Warmblood
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Swedish Warmblood
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Swiss Warmblood
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Australian Warmblood
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Irish Sport Horse
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Cleveland Bay
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Württemberger
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Zangersheide
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Knabstrupper
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Orlov Trotter
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Camargue
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Icelandic Horse
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Pony of the Americas
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Quarter Pony
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Miniature Horse
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Clydesdale
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Shire
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Percheron
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Belgian Draft
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Suffolk Punch
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American Cream Draft
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Ardennes
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Breton
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Boulonnais
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Comtois
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Dutch Draft
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North Swedish Horse
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Norwegian Fjord
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Haflinger
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Gypsy Cob
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Irish Draught
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Welsh Pony and Cob
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Connemara Pony
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New Forest Pony
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Dartmoor Pony
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Exmoor Pony
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Shetland Pony
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Highland Pony
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Fell Pony
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Dales Pony
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Australian Pony
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Finnhorse
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Black Forest Horse
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