Horses require vitamin E in their diets for many biological functions. One of vitamin E’s most well-known roles is as a powerful antioxidant that promotes health of muscle and nerve cells. Because it is fat-soluble, vitamin E must be consumed with dietary fat in order to be properly absorbed in the body. Sources of vitamin E include fresh pasture, good-quality hay, and fortified concentrates.
Forms of Vitamin E
Not all vitamin E is the same. There are several forms, or isomers, of vitamin E, but only natural vitamin E contains a form known as d-alpha-tocopherol. A recent study suggested that natural vitamin E may be superior to synthetic versions in mitigating oxidative and muscle cell damage in exercising horses compared to the synthetic version*.
Numerous vitamin E supplements are available, but differences in their bioavailability have been noted by researchers. Natural vitamin E, or d-alpha-tocopherol, has been scientifically proven to be the most bioavailable form. Synthetic vitamin E, or dl-alpha-tocopherol, contains a mixture of several isomers of vitamin E, not all of which are readily absorbed, hence it is less bioavailable. Water-dispersible, natural d-alpha-tocopherol increased serum concentration of vitamin E within one week, compared to a powdered form that took seven weeks to reach a comparable concentration in horses with low vitamin E status**.
According to Nutrient Requirements of Horses (NRC, 2007), an 1100-lb (500-kg) horse in light to moderate exercise requires 800-900 IU of vitamin E per day. This is often achieved with a balanced diet of good-quality hay or pasture. However, the vitamin E content of hay begins to decline as soon as it is harvested and stored. Vitamin E losses can be as high as 50% after one month of storage+. Vitamin E content of pasture can also vary by day, species, and season. Horses on low- or no-grain diets may therefore benefit from vitamin E supplementation if pasture or hay is of low quality (or if hay has been stored for several months).
Vitamin E does not appear to be toxic to horses, although the NRC sets a safe upper limit at 1,000 IU per kilogram of dry matter fed. A Brooks Feeds nutrition advisor can make a recommendation for the appropriate amount to supplement your individual horse.
Vitamin E incorporates into cell membranes, where it can protect the cell against damage by free radicals. Horses on hay- or pasture-only diets, those with muscle injuries or neurological concerns, and those in moderate to heavy work could benefit from a consistent, high-quality natural vitamin E supplement such as Nano•E.
*Fagan, M.M., R. Pazdro, J.A. Call, A. Abrams, P. Harris, A.D. Krotky, and K.J. Duberstein. 2017. Assessment of oxidative stress and muscle damage in exercising horses in response to level and form of vitamin E. Journal of Equine Veterinary Science. 52:80-81.
**Brown, J.C, S.J. Valberg, M. Hogg, and D.J. Finno. 2017. Effects of feeding two RRR-alpha-tocopherol formulations on serum, cerebrospinal fluid and muscle alpha-tocopherol concentrations in horses with subclinical vitamin E deficiency. Equine Veterinary Journal. DOI: 10.1111/evj.12692.
+McDowell, L.R. 1989. Vitamin E. In: McDowell, L.R. ed. Vitamins in Animal Nutrition. San Diego, CA: Academic Press, Inc.; pp. 93-131.