Exertional rhabdomyolysis, otherwise known as "tying up," is a term used to describe a variety of muscle disorders in the equine athlete. Horses affected by tying up have varying degrees of muscle cramping or muscle soreness, with the more severe cases accompanied by elevated respiratory and heart rates, dark colored urine, and reluctance to move or stand.

A balanced diet, including vitamins and minerals, is just one factor in the treatment and prevention of tying up. Here are some ways that two specific nutrients, selenium and vitamin E, can help prevent or alleviate symptoms of tying up:

• Selenium: During exercise several chemical processes occur, allowing the horse's muscle to utilize energy. However, those same processes produce oxidation-induced damage by free radicals. Selenium is a vital part of glutathione peroxidase--an enzyme that prevents free radicals from causing cellular damage. Deficiencies in selenium will directly relate to a decreased ability to rid the muscle of these detrimental substances.
• Vitamin E (alpha-tocopherol): Most commonly found in green growing forage, vegetable oils, and synthetically in grains and supplements, vitamin E works in cooperation with selenium as a part of glutathione peroxidase. In addition, vitamin E is thought to play a role in cellular defense of free radicals by incorporating in cell membranes and preventing lipid peroxidation.
• Selenium and vitamin E work together, and one cannot replace the other. Studies have shown that if there is a selenium deficiency, higher levels of vitamin E are needed. Conversely, if there is a vitamin E deficiency, more selenium will be needed. The optimum amounts of selenium and vitamin E required in this type of situation is significantly greater to prevent signs of damage.

Work with a veterinarian or equine nutritionist to ensure each horse is consuming adequate selenium and vitamin E in its diet. In the event a horse is deficient in either nutrient, work with a professional to select a supplement that provides the required vitamin E and selenium levels to keep the animal healthy.

Take Home Message

Selenium and vitamin E work together to prevent tissue damage from free radicals produced during exercise by the enzyme glutathione peroxidase and cellular membrane components. It's important to ensure the diet of performance horses is balanced for both vitamin E and selenium.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.