This study by Kentucky Equine Research was designed to determine the effects of three rations (low grain, fat, high grain) on plasma creatine kinase (CK) activity and lactate concentration in Thoroughbred horses with recurrent exertional rhabdomyolysis (RER).

The study used five Thoroughbreds with RER and three healthy Thoroughbreds (control horses). Rations were formulated to meet (low-grain and fat rations) or exceed (high-grain ration) daily energy requirements. Each ration was fed to horses in a crossover design for three weeks. Horses were exercised on a treadmill Monday through Friday; maximum speed on Monday and Friday was 11 m/s (6% slope), on Tuesday and Thursday was 9 m/s, and on Wednesday was 4.5 m/s. Plasma CK activity and lactate concentration were determined before and after exercise.

Horses with RER fed the high-grain ration had significantly greater CK activity and change in CK activity four hours after exercise compared with those fed the low-grain ration. Horses with RER exercised at the trot or canter had significantly greater increases in CK activity compared with those exercised at the gallop. Plasma lactate concentrations after exercise were similar in control and affected horses. Lactate concentration and CK activity were not correlated in horses with RER.

Rations high in grain and formulated to exceed daily energy requirements may increase episodes of rhabdomyolysis in Thoroughbred horses susceptible to RER.

This report of KER’s 2000 research was published in American Journal of Veterinary Research.

Read the entire research paper, titled Effect of Ration and Exercise on Plasma Creatine Kinase Activity and Lactate Concentration in Thoroughbred Horses with Recurrent Exertional Rhabdomyolysis.

Visit Kentucky Equine Research at ker.com.