Vitamin E and Vitamin E-Responsive Myopathy

Vitamin E is a fat-soluble vitamin and an important antioxidant for horses. It helps maintain a healthy immune system and supports normal nerve and muscle function.

Horses cannot synthesize vitamin E in their body. It’s found in fresh, green grasses and forage. Horses on lush pasture often get enough vitamin E by grazing fresh grass. Cutting grasses and forages to harvest hay causes the vitamin E to quickly degrade which continues as the hay is stored. Hay stored for longer periods of time or poor-quality hay will have lower vitamin E content. If your horse is fed mostly hay, they likely have low vitamin E intake.

Vitamin E deficiency can cause your horse to be more likely to tie-up after exercise or to become sick with frequent coughs and to recover slowly. It can also make some equine neurological disorders worse. Long-term vitamin E deficiency will cause oxidative damage to the nerves that transmit motor movements to muscles.

Chronically deficient horses may experience weight loss, muscle atrophy, a dry, stiff coat and decreased performance. They may begin to spend more time lying down, have muscle tremors or hind limb stiffness, drag their toes or a low head carriage.

There are several diseases associated with Vitamin E deficiency. One example is Vitamin E-responsive myopathy which been identified in horses that show clinical signs of equine motor neuron disease (EMND) such as weakness, muscle loss, and weight loss but do not have the microscopic changes in tailhead muscle that are seen with EMND.

Your Vet can test for serum and muscle concentrations of vitamin E. Some horses have normal to high levels in their serum but low levels in the muscle. Horses with vitamin E-responsive myopathy may have abnormal staining for mitochondrial function. Horses affected by Vitamin E responsive myopathy respond well to supplementation and can make a complete recovery.

Every horse is unique and will metabolize Vitamin E differently. Nutritionists recommend having your Vet test Vitamin E levels 1-2 times per year, so that you can supplement only if it’s needed.

Natural forms of Vitamin E can be used more readily by the horse’s tissues. Natural forms are typically listed with a “d” prefix, like d-alpha-tocopherol, d-alpha tocopheryl acetate or d-alpha tocopheryl succinate. Synthetic vitamin E supplements will have “dl” as the prefix, such as dl-alpha tocopherol.

While the risk of toxicity from high-dose vitamin E supplementation is considered low in horses, some issues can arise if it’s over fed including problems with blood clotting, bone mineralization and can affect beta-carotene absorption.

Vitamin E provides critical protection for your horse’s neuromuscular system. With proper forage, good quality hay, and supplements if necessary, you can be sure your horse has enough vitamin E and will maintain good health for a long, productive life.

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