When shopping for equine supplements, don’t forget about good ol’ Vitamin E! The darling of nutritionists and the cosmetic industry, this plant-derived vitamin is essential for the working equine, as well.

As savvy horse owners know, Vitamin E is abundant in fresh, green pasture. But why is this vitamin so important? Does turnout provide enough of it? And if not, does it really matter where your horse gets it?

Let’s start with the reasons your horse needs Vitamin E. According to equine nutritionist Katie Young, Ph.D., it “plays an important role in nerve and muscle function, working as part of the nonenzymatic defense system of the body.” So if you want to maintain normal muscle function in your horse and help prevent muscle disorders, get on that Vitamin E train! You see, Vitamin E functions as a primary antioxidant in horses, especially during exercise. Although oxidation is a normal metabolic process, it produces free radicals, which, as Young explained, are compounds that can be damaging to cells. Working or performance horses “may experience muscle soreness or stiffness following exercise—and longer recovery periods, if natural antioxidant stores are inadequate,” she said. The good news: “Supplementation of antioxidants, such as vitamin E, can help in reducing the potential damage caused by free radicals in exercising horses.”

But let’s face it: Most working horses don’t have 24/7 access to pasture, and even for those that do, the quality of pasture varies considerably with the location, the season and other factors. Of course, the same goes for hay, which loses Vitamin E activity within months of cutting.

Bioavailable or Bust

That’s where oral supplements come in. “Sure,” you might say. “My supplement contains Vitamin E.” But is it bioavailable (meaning absorbable in a form that can be readily metabolized)? Your horse’s ability to absorb this vital antioxidant depends in part on its source.

According to Young, powdered synthetic vitamin E, the most common form in many feeds and supplements, is a mixture of vitamin isomers, “some of which are more bioavailable than others.” By contrast, she said, “Natural vitamin E contains only the form d-alpha-tocopherol, which is highly bioavailable (the most biologically active form of vitamin E).” Further, she explained, researchers have suggested that natural vitamin E outperforms synthetic vitamin E when it comes to minimizing oxidative and muscle cell damage in exercising horses.

In addition, research points to a water-dispersible, natural form of Vitamin E reaching serum concentration (therapeutically active levels in the blood) much faster than the powdered form.

Amounts Count

So your horse is getting natural Vitamin E—that’s great. But is he getting enough? The amounts of Vitamin E in most commercial feeds are varied, and “rarely in quantities that will meet a horse’s total requirement alone, especially for working horses,” Young maintained.

At present, the National Research Council recommendations to meet daily minimum maintenance requirements are 500 IU of Vitamin E per day for an 1,100 lb (500 kg) horse, and 800-1000 IU per day for a working horse. From additional sources*, vitamin E recommendations include supplementing 3,000-5,000 IU per 1,100 lb (500 kg) horse six to 12 hours prior to competition or a stressful event, 5,000 IU/day to support horses diagnosed with EPM, and 2,000-3,000 IU/day for horses with muscle myopathies. 

Because NRC recommendations don’t discriminate between natural and synthetic sources of Vitamin E, it’s up to you to be a shrewd consumer. Given the many ways the vitamin is listed on feed and supplement labels, it can be tricky to figure out which is which. So don’t be afraid to do your research, read the product literature and ask questions of the manufacturer.

Remember, your horse’s health is at stake—and Vitamin E from the best sources, in a readily available form and in appropriate amounts can help maintain that health.

*Additional sources include: Kentucky Equine Research, publications authored by Dr. Stephanie Valberg, and Geor, Harris and Coenen Equine Applied and Clinical Nutrition

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