Management Decisions Affect Muscle Health in Racehorses

Muscle problems, especially different forms of tying-up, can significantly, and sometimes permanently, sideline racehorses. Though the prevalence of recurrent exertional rhabdomyolysis (RER) has been studied in different parts of the world, researchers in New Zealand set out to determine feeding and management strategies for racehorses with RER.*

A hundred Thoroughbred and Standardbred trainers were surveyed and the following information collected: number of horses in full work, number of horses identified with RER, types of feed, feeding rates, and turnout time.

Prevalence of RER in the racehorse population was found to be 8.4%, with 8.8% of Thoroughbred horses and 7.9% of Standardbred horses showing clinical signs of the muscle disease. The greatest prevalence was found among Standardbred fillies, Thoroughbred fillies, and Thoroughbred mares.

One strategy employed by trainers to combat RER revolves around nutrition, particularly concentrate intake. Thoroughbred trainers, for example, fed an average of 14.3 lb (6.5 kg) feed per day to those horses without RER, while horses diagnosed with RER were fed an average of 12.3 lb (5.6 kg), which is nearly 14% less feed per day. Standardbred trainers had a far greater disparity: horses without RER were fed an average of 15.2 lb (6.9 kg), while those with RER were fed an average of 9.2 lb (4.2 kg), a 39% difference.

A second management strategy involves turnout time. Both Thoroughbred and Standardbred trainers gave RER horses more free exercise than those without muscle problems.

Nutritional management of horses with RER may include the following suggestions, some of which were used by trainers in the aforementioned study:

  • Replacing much of the grain in the diet with a low-starch, high-fat feed such as Re-Leve.

  • Increasing dietary fat as an energy source, which serves a dual purpose of providing energy for high-performance horses, like racehorses, and calming fractious or nervous horses.

  • Verifying vitamin E and selenium intake is adequate, as both act as antioxidants and can each offset a deficiency of the other. Choose a natural, water-soluble vitamin E product like Nano-E for optimal delivery of this nutrient.

  • Maximizing turnout, often with a compatible companion.

“Over the last 20 years, researchers have made great leaps in understanding how best to feed horses with RER and other muscle problems, sometimes to the point of completely eradicating clinical signs of the disease and allowing the horse to perform normally,” said Catherine Whitehouse, M.S., a nutrition advisor for Kentucky Equine Research.

Learn more about managing metabolic diseases in Nutritional Management of Metabolic Diseases, a booklet developed by Kentucky Equine Research.

More questions? Would you like one-on-one assistance? Contact a Kentucky Equine Research nutrition advisor today.

*Wood, L.J., and C.W. Rogers. 2018. A comparison of feeding and management practices associated with Thoroughbred and Standardbred race horses displaying clinical signs of recurrent exertional rhabdomyolysis. In: Proc. Australasian Equine Science Symposium 7:12.