Reduce the risk of myositis with the right diet 

According to the U.S. National Library of Medicine (2016) “A metabolic disorder occurs when abnormal chemical reactions in your body disrupt this process [metabolism].”
Recurrent Exertional Rhabdomyolysis (RER) is a “syndrome of muscle pain and cramping associated with exercise” (Valberg, 2020). And literally means that the muscle cells are dying (dissolving) with exercise.

Diagnostic to confirm RER starts with a physical exam, even though “A diagnosis of rhabdomyolysis is usually made by measuring the activity of the enzymes creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate transaminase (AST) in serum.” (Valberg, 2002). Based on clinical signs (among other signs), genetic testing can be done to check for Polysaccharide Storage Myopathy (PSSM) or Glycogen branching enzyme deficiency (GBED). A muscle biopsy can also be done to diagnose the causes of the horse’s rhabdomyolysis. (Valberg, 2020)

Even though there are several forms of RER, this disorder has been linked to diet and exercise, some diet manipulation can be applied to lower the risks.
The carbohydrate amount of the diet should be lowered. High fat, low carbohydrate (with quality fiber) diets have shown a reduction of the horse’s heart rate and a pack cell volume that reveal a more relaxed state, and that implies a lower risk of RER, while being able to meet energy demands. (MacLeay et al., 1999)

Electrolyte deficiencies are usually due to high cereal, low forage diet, especially regarding to potassium (K) levels (Pagan, 2009), sodium (Na) supplementation have been shown to reduce RER symptoms occurrence, sodium chloride (NaCl) and calcium (Ca) supplementation have given really good results. (Harris & Snow, 1991)
Chromium (Cr) supplementation have been said to reduce nervousness and improves glucose storage and utilisation and thus can be beneficial to RER horses. (Pagan, 2009)

  • Make sure that the horse does not carry any genes predisposing to myositis
  • Limit the amount of starch in the diet (carbohydrates)
  • Choose a high-fat, high-fibre diet
  • Check electrolyte levels
  • Provide a salt lick (if possible, preferably classic white)



Harris, P.A. and Snow, D.H. (1991) “Role or electrolyte imbalances in the Pathophysiology of the equine Rhabdomyolysis Syndrome.,” in Equine Exercise Physiology. S.G.B. Lindholm, A.F. Jeffcott J.R.: Ed. Person, pp. 435–442.

MacLeay, J.M. et al. (1999) “Effect of diet on thoroughbred horses with recurrent exertional rhabdomyolysis performing a standardised exercise test,” Equine Veterinary Journal [Preprint]. Available at:

Pagan, J.D. (2009) Advances in equine nutrition IV. Thrumpton, UK: Nottingham University Press.

U.S. National Library of Medicine (2016) Metabolic disordersMedlinePlus. U.S. National Library of Medicine. Available at: (Accessed: December 16, 2022). 

Valberg, S. (2002) “A Review of the Diagnosis and Treatment of Rhabdomyolysis in Foals,” AAEP PROCEEDINGS, Vol. 48, pp. 117–121. 

Valberg, S. (2020) Exertional rhabdomyolysis (ER)The College of Veterinary Medicine at Michigan State University. Available at: (Accessed: December 16, 2022). Valberg, S. (2020) Recommended diagnostic work-up for MyopathiesThe College of Veterinary Medicine at Michigan State University. Available at: (Accessed: December 16, 2022).

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