Vitamin E for Neurologic Disease in Horses (AAEP 2010)

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."

Vitamin E deficiency has been linked to equine degenerative myeloencephalopathy (EDM) and equine motor neuron disease (EMND). Also, Kane noted that possibly due to underlying oxidant damage from their neurologic disease, affected horses might have greater need for vitamin E than unaffected horses. Thus, promoting high enough levels of alpha-tocopherol (a specific form of vitamin E) in a horse's blood and cerebrospinal fluid (CSF, the fluid around the brain and spinal cord) is important for preventing and treating these neurologic diseases and potentially others.

"It's highly recommended that young horses at risk for these neurologic diseases, or mature horses with neurologic disease, be supplemented with vitamin E," said Kane. "Supplementing stallions might help their foals, too (this practice reduced EDM incidence by 75% in one study he referenced)."

He discussed two studies of water-soluble vitamin E supplementation in horses (completed at UC Davis School of Veterinary Medicine); in the first study researchers found that giving horses 10,000 IU (international units) of natural micellized (processed for greater bioavailability) vitamin E compared to 1,000 IU unsurprisingly resulted in higher concentrations of vitamin E in both blood and cerebrospinal fluid. However, the 10x dose did not give 10 times the serum/CSF concentrations of vitamin E; the increase in E concentration in each horse was 1.3-3.4-fold across both groups.

In the second study investigators evaluated natural micellized vs. synthetic vitamin E use by comparing blood serum and CSF levels of alpha-tocopherol before and during 14 days of supplementation with 10,000 IU of natural vitamin E, 10,000 units of synthetic vitamin E, or 5,000 IU of natural vitamin E daily. The natural vitamin E came out on top, yielding higher levels of alpha-tocopherol in study horses' blood and CSF even when given at half the synthetic dose. Indeed, the synthetic form did not even significantly raise alpha-tocopherol levels in CSF above baseline at the 14-day mark.

"Supplementation of a water-soluble natural micellized alpha-tocopherol should be used instead of synthetic vitamin E when treating horses with neurologic disorders," Kane concluded. "Consider giving this to horses with neurologic disease at 5-10 IU/lb, to reach serum alpha-tocopherol levels greater than 6 µg/mL."

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