The Importance of Vitamin E in Your Horse's Diet

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Question: My 19-year-old, 1000-pound gelding is showing occasional awkwardness in his left hind leg. My vet terms this ataxia due to probable equine degenerative myeioencephalopathy (EDM). I am located in north-central Florida--he is never stalled and has plenty of good forage on coastal bermuda grass. However, I have read that EDM can be due to a vitamin E deficiency in forage. If vitamin E therapy will improve this condition, I want to do it. How effective would that be? How much should be given? Most vitamin E supplements I find in equine supply catalogs are combined with selenium, which supposedly makes the E more effective. But I've heard that selenium is quite toxic if given in excess. Should I look for a supplement that contains E only?

Lush pastures. Courtesy KHP

Horses with limited access to fresh greens can become deficient in vitamin E.

Answer: Vitamin E is an important fat soluble nutrient for horses. The need for it has been traditionally connected to its relationship with selenium and muscle problems such as tying up. The main research published over the years has pertained to this use of vitamin E. However, research done mostly in non-equines, has shown that vitamin E is an extremely important nutrient for many body functions.

Vitamin E is one of the most important antioxidants, which are nutrients that protect the body from free radicals. To understand the role of antioxidants, think about rust. A piece of metal rusts and becomes less strong over time. Rust is oxidation. If parts of the body "rust" or oxidize they become less healthy, and we require compounds that are antioxidants to fix them. So vitamin E helps keep many parts of the body functioning optimally.

Vitamin E plays an important role in the immune system, reduces cellular aging, keeps the blood flowing well, helps protect lung tissue against air pollution, protects the nervous system, helps lower the risk of some cancers, helps heart function and is especially important in reproduction and fertility. And this is just a partial list.

Horses can easily become deficient in vitamin E because one of its main sources in the equine diet is fresh greens (grass, weeds, etc). Many horses eat stored, dried greens such as hay. Much of the vitamin E content is destroyed as the hay is stored, especially because hay lofts tend to be very hot environments. Horses in northern climates are even more likely to be deficient due to the short growing season and long hay feeding season.

Several diseases besides tying up are linked to vitamin E deficiency: the EDM your vet has mentioned, Equine Motor Neuron Disease (EMND) and white muscle disease of foals. All of these are relatively uncommon diseases in their full-blown state, but may exist in a mild form in more horses than we think.

Vitamin E supplementation is easy and very safe to do. You are correct in your concern about the selenium content of most supplements. If you need to supplement vitamin E, you want to use pure vitamin E. The levels for correcting a deficiency or treating a condition range from 1000 IU to 10,000 IU. In many cases, I use about 8,000 IU to correct a problem, then drop the dose down to 1,000-5,000 depending on the horse.

Also important is the type of vitamin E: It is much better to use the natural form, listed as d-alpha tocopherol, while synthetic E is dl-alpha tocopherol. The natural form is absorbed significantly better by the body and is used in all biochemical pathways, while the synthetic is less well-absorbed and is not used as completely. There are some equine supplement companies that use the natural form (Advanced Biological Concepts, SmartPak, Kentucky Equine Research are a few). Human health food stores can be a great source. Do not buy the cheapest you can find as Vitamin E is a sensitive nutrient and is easily damaged by poor quality control.

However, after all this talk about vitamin E, there are also a couple other things to check out in a 19-year-old horse that may help his ataxia. He may have fallen or mildly injured his back. This is a very common cause of hind limb weakness or ataxia. A trained veterinary chiropractor can help diagnose this type of condition. Some horses become weak behind as they age and will benefit from acupuncture, even if they have a bit of neurological deficits from some other disease (Alternative Healthcare Organization Links).

Dr. Joyce Harman is a veterinarian and respected saddle-fitting expert certified in veterinary acupuncture and veterinary chiropractic; she is also trained in homeopathy and herbal medicine. Her Harmany Equine Clinic is in northern Virginia. Visit her online shop, blog and Facebook page.