Exertional Rhabdomyolysis in Horses: Welfare and Prevention

Tying-up (exertional rhabdomyolysis) causes severe muscle pain and damage in exercising horses — prevention through diet and conditioning significantly reduces welfare harm.

Key Facts

• ER causes rapid-onset severe muscle pain and stiffness during or after exercise
• Mares, thoroughbreds, and horses with certain genetic conditions (RER, PSSM) are predisposed
• Affected horses show sweating, muscle trembling, reluctance to move, and hard painful muscles
• Urine may turn red-brown from myoglobin released from damaged muscle
• Prevention through carbohydrate restriction, conditioning, and electrolyte management reduces recurrence

Welfare Considerations

Exertional rhabdomyolysis causes acute severe welfare suffering — the muscle breakdown releases myoglobin and inflammatory mediators that cause intense muscle pain, stiffness, and the distress of being unable to move normally. Horses with ER stand anxiously, tremble, and resist movement. The myoglobinuria (red-brown urine) indicates massive muscle damage and kidney injury risk. Management requires immediate rest, pain control, fluid therapy to protect the kidneys, and investigation of predisposing factors. Horses with recurrent ER benefit from veterinary workup to identify the specific form — RER (thoroughbred-type) or PSSM — and implement targeted dietary and exercise protocols that dramatically reduce recurrence and ongoing welfare burden.

What You Can Do

• Stop exercise immediately and call your veterinarian for any horse showing stiffness and reluctance to move during work
• Never attempt to walk a tying-up horse to 'walk it off' — movement worsens muscle damage
• Request muscle enzyme testing (CK, AST) to quantify damage and guide management
• Investigate predisposing form (RER vs PSSM) through muscle biopsy or genetic testing
• Implement a low-carbohydrate diet and structured conditioning program for chronically affected horses