Vitamin E and selenium are nutrients that work as partners to help keep your horse healthy and in tiptop shape. Together they form part of the enzyme glutathione peroxidase, working to help immune function and destroy or damage free radicals. This enzyme is also important in maintaining muscle health. If you need to supplement selenium, you should usually use vitamin E with it.
VITAMIN E. Vitamin E is a fat-soluble vitamin. Generally, you need to be more careful feeding fat-soluble vitamins than water-soluble vitamins. With water-soluble vitamins, any excess eaten is simply urinated out. Fat-soluble vitamins can build up in your horse's body and cause toxicity. While the fat-soluble vitamins A and D have been shown to cause toxicity in the horse, vitamin E has not.
Vitamin E is found naturally in your horse's diet in fresh pasture. There will be some vitamin E in cut hay, but the amount degrades over time. Many grain mixes have at least some vitamin E added.
Most nutrition experts suggest that horses do best with about 1 IU of vitamin E per pound of feed. On the other hand, the NRC (National Research Council) suggests 1 IU per kg of body weight for maintenance. that's about half what many nutritionists suggest.
The exact amount of vitamin E your horse needs will vary with how hard he is working, if she is pregnant, if he has any injuries etc. There is no one-fits-all recommendation for vitamin E supplements.
Two neuromuscular disease problems can show up in horses that are vitamin E deficient. These are EDM or equine degenerative myeloencephalopathy and EMND or equine motor neuron disease.
You may hear EDM referred to as ?white muscle disease.? This tends to show up in young horses or foals and affect their heart and skeletal muscle. Supplementing vitamin E and selenium can help to prevent and treat this problem.
EMND tends to show up in horses over two years of age. These horses may tremble, shift weight when standing and develop muscle wasting. Supplementation is used as part of therapy.
Horses with illnesses such as EPM (equine protozoal myelitis) and horses that ?tie up? with exertional rhabdomyolysis sometimes benefit from some extra vitamin E in their diets (see April 2012, EPM). You can also use vitamin E topically on wounds and proud flesh.
Vitamin E can be supplemented in two forms. The natural form is d-alpha-tocopherol. This is the most helpful to your horse, but it does have a short shelf life. The synthetic form is dl-apha-tocopherol. This is more stable but you may need to supplement it at a higher rate (up to one third higher) to compensate for the lower activity.
SELENIUM. Selenium is the trickier half of the partnership. it's? also involved in thyroid function, helping with the production of T3.
Selenium content varies greatly in regions and soils across North America. If you live in an area with selenium-deficient soil, the forage and grain you feed your horse will tend to be low in this mineral. On the other hand, too much selenium can definitely be toxic.
The case a few years ago of the 20 polo ponies that died in Florida was due to a supplement that was incorrectly compounded and resulted in selenium toxicity. Too much selenium can cause colic, diarrhea, ?blind staggers? with horses appearing to be blind and increases in both the heart rate and the respiratory rate. Death can result.
Mild selenium toxicity can cause ?alkali disease.? You may notice your horse has hooves cracking along the coronary band or is losing hair in his mane and tail. The excess selenium switches in for sulfur, so the keratin that is produced is of inferior quality. This problem will resolve when the diet is adjusted.
In general, horses should get about 1 to 3 mg of selenium per day. Hard-working horses (racehorses, endurance horses) may go as high as 5 mg. The tricky part is that you must look at all sources of selenium, including his hay, pasture, grains and supplements.
Selenium deficiency can lead to ?white muscle disease,? just as vitamin E can. There is an excellent map of selenium levels in soil in North America at http://www.ansci.cornell.edu/plants/toxicagents/selenium_map.html. The main areas for deficient soil include the Northeast, the Ohio Valley, northwestern US and some areas of the Southeast.
If you live in a selenium-deficient area, ask your vet about supplementing selenium for any pregnant mares to help prevent white-muscle disease in your foals and for hard-working horses.
Ideally, you should do a feed analysis, including selenium content, each year. On a drought year, selenium-deficient areas may have more selenium than usual in their plants as the roots go down deeper into the soil.
Many feed companies offer forage analysis at discounted rates. You can also contact your local Cooperative Extension about having your feeds analyzed. Commercially, you can contact Equi Analytical (www.equi-analytical.com, 877-819-4110), Litchfield Labs (www.litchlab.com, 517-542-2915), or Uckele (www.uckele.com, 800-248-0330). Prices run about $40 to $60. So, while tHere's some cost involved, it's better that than ill horses, which get really expensive, really quickly!
BOTTOM LINE. Vitamin E and selenium are important for your horse's muscle and overall health. Getting the dietary balance perfect may take some tweaking on your part. You also need to be careful since so many supplements automatically add both selenium and vitamin E. If your horse just needs more vitamin E, you need to find a supplement that just adds that. See recommended vitamin e and selenium products.
Article by Contributing Veterinary Editor Deb Eldredge, DVM.