You might already know that vitamin E is a powerful antioxidant that helps protect cell membranes and tissues from damage by reactive free radical molecules. You might even know that it's been recommended to help treat several neurologic diseases in horses. But did you also know that just feeding vitamin E might not be enough, and that having the right source of that vitamin E is also key?

During the 2010 American Association of Equine Practitioners convention, held Dec. 4-8 in Baltimore, Md., Ed Kane, PhD, a researcher and consultant in animal nutrition, presented a review of literature on vitamin E and its effects on horses with neurologic disease.

"Horses on pasture or those that have access to fresh green forage get enough vitamin E," he began. "But most horses these days are fed stored forages and grains, and they might not get enough. Confined horses, or those on poor or winter pasture, often need vitamin E supplementation.

"All sources of vitamin E are not the same," he went on. "Natural and synthetic forms have chemically different structures. Synthetic vitamin E contains equal amounts of eight stereiosomers (different chemical structures) of vitamin E, of which only one is identical to the natural RRR-isomer. The body preferentially transports and incorporates the natural isomer, thereby making the bioavailability of natural vitamin E greater than an equal quantity of synthetic vitamin E