Vitamin E is unique. It is pivotal in the proper functioning for most systems of the horse's body. The reproductive, muscular, nervous, circulatory and immune systems all rely on vitamin E to some extent. It is in every cell and is distinctive in its supportive role within the spinal cord, brain, liver, eyes, heart, skin and joints. Fats, which are an integral part of all cell membranes, are vulnerable to damage through lipid peroxidation by free radicals. As the major fat-soluble antioxidant, vitamin E utilizes its lipophilic nature by incorporating itself into cell membranes where it protects unsaturated lipids and other susceptible membrane components against oxidative damage. Vitamin E is uniquely suited to intercept peroxyl radicals and thus prevent a chain reaction of lipid oxidation.

Vitamin E is actually made up of two classes of molecules: tocopherols (saturated) and tocotrienols (unsaturated). Although both are available in the diet in several forms, alpha-tocopherol is the form most often found and preferentially absorbed in the body. For other vitamins, a synthetic source is basically identical to the natural source for both efficacy and structure, but this is not the case for vitamin E. The natural source of alpha-tocopherol is clearly preferred biologically in several ways. It is recognized to have significantly higher biological activity, is transported more quickly and stays in the tissues twice as long when compared to the synthetic version. When natural vitamin E is used in feeds and supplements, it is usually labeled as "natural" or "d" (for example, d-alpha-tocopherol or d-alpha-tocopheryl acetate, the esterified and stabilized form).

As it is not synthesized within the horse, vitamin E is considered an essential nutrient, and therefore daily consumption is required to maintain adequate blood and tissue levels for cell protection. Fresh, green pasture grass, particularly alfalfa, is an excellent source of natural vitamin E. However, the levels of vitamin E plummet a staggering 86 percent when it is cut, dried and baled for hay. Other factors, such as maturity of pasture and length of storage time once baled dramatically diminish the quantity of vitamin E, with levels being seen to dive tenfold below that of fresh forage.

For all horses that have limited or no access to quality pasture grass, supplemental vitamin E is necessary. This is especially critical management information for newborn foals and growing horses, gestating and lactating mares and performance horses that are being fed stored hay and kept stalled. As the vitamin E requirement is greater for these classes of horses, consuming hay only and being kept in confinement would make them more susceptible to vitamin E deficiency.

Chronic suboptimal vitamin E consumption may result in poor stress tolerance, subpar athletic performance, poor wound healing, muscle weakness and general suppressed immune function. Although most horses with a vitamin E deficiency may not show symptoms, true vitamin E deficiency is linked to several disease states, including several neuromuscular diseases. In young horses, these diseases include nutritional myodegeneration, neuroaxonal dystrophy and equine degenerative myeloencephalopathy. Adult horses may develop vitamin E deficient myopathy or equine motor neuron disease. The symptoms of severe vitamin E deficiency include ataxia, peripheral neuropathy, muscle weakness and fasciculations and damage to the retina of the eye. Measuring blood serum or plasma alpha-tocopherol concentrations is the easiest way to discern if the horse has adequate vitamin E levels. Adequate alpha-tocopherol concentrations are considered to be more than 2 ug/ml, marginal ranges are from 1.5 to 2 ug/ml and a concentration below 1.5 ug/ml is considered deficient. Click here for the rest of the article.