Horse Exertional Rhabdomyolysis: Welfare and Prevention

Exertional rhabdomyolysis (tying-up) causes acute muscle pain and damage in exercised horses, with prevention requiring management of dietary, genetic, and training factors.

Key Facts

Rhabdomyolysis involves acute muscle fiber breakdown during or after exercise, causing severe pain and stiffness
Affected horses show stiffness, reluctance to move, muscle trembling, sweating, and dark urine from myoglobin
Two main syndromes are recurrent exertional rhabdomyolysis (RER) in Thoroughbreds and PSSM in draft breeds
PSSM is caused by abnormal glycogen storage and is managed with diet modification and regular exercise
RER appears to involve calcium dysregulation in muscle and is worsened by electrolyte imbalance and stress
Treatment requires rest, pain relief, IV fluids, and nutritional management; severe cases require hospitalization

Welfare Considerations

Acute rhabdomyolysis episodes cause severe muscle pain that is acutely distressing for affected horses. Horses attempting to move despite pain risk worsening muscle damage and kidney injury from myoglobin excretion. Recurrent episodes in susceptible horses represent repeated welfare compromises that require active management rather than hoping episodes will resolve. Identifying the specific syndrome (RER vs PSSM) enables targeted dietary and management interventions that substantially reduce recurrence rates and improve long-term welfare.

What You Can Do

Stop exercise immediately and call a vet if your horse shows stiffness, sweating, or reluctance to move after work
Never force a horse with suspected rhabdomyolysis to walk if it is in severe distress
Work with an equine nutritionist to formulate a diet appropriate for your horse's specific syndrome type
Maintain consistent daily exercise to prevent the dietary carbohydrate loading that worsens PSSM episodes
Genetic testing for PSSM1 is available and recommended for draft breeds with recurrent tying-up