DIETARY CONTROL OF EXERTIONAL RHABDOMYOLYSIS IN HORSES

Objective-To determine whether feeding a low-carbohydrate, high-fat di et would decrease severity of exercise-induced muscle injury in horses with exertional rhabdomyolysis. Animals-19 horses with a history of e xertional rhabdomyolysis. Design-Case series. Procedure-Specimens of t he semitendinosus or semimembranosus muscle were obtained for histolog ic examination, and serum creatine kinase (CK) and aspartate transamin ase (AST) activities 4 hours after exercise were determined. Horses we re then fed a low-carbohydrate, high-fat diet, and serum CK and AST ac tivities 4 hours after exercise were reevaluated at approximately mont hly intervals for 3 to 6 months. Results-Serum CK and AST activities 4 hours after exercise were high before any change in diet. All 19 hors es had evidence of chronic myopathic change and abnormal glycogen accu mulation in muscle biopsy specimens; ii horses also had evidence of co mplex polysaccharide accumulation. Adaptation to diet change required approximately 3 to 6 months. Sixteen horses did not have any episodes of exertional rhabdomyolysis after 3 to 6 months of diet change, and 3 horses had mild episodes of exertional rhabdomyolysis following eithe r a reduction in dietary fat intake or restriction in exercise. Postex ercise serum CK and AST activities 3 to 6 months after the change in d iet were significantly less than initial values. Clinical implications -Results indicated that exertional rhabdomyolysis may be a result of a bnormal carbohydrate metabolism in some horses. Feeding a diet with lo w carbohydrate and high fat content may reduce severity of exercise-in duced injury in some horses with exertional rhabdomyolysis.