Tocopherols including Vitamin E

The Tocopherols are a class of fat soluble antioxidants, four of which, along with four tocotrienols make up Vitamin E. These eight different physical forms (d and l stereoisomers) are designated alpha, beta, delta, and gamma which have differing degrees of biological activity. The naturally occurring form, technically RRR d alpha- tocopherol has the highest activity as measured by International Units (IU) and in horses is approximately 3.4 times more potent than the synthetic dl form of alpha tocopherol.

Note. The International Unit I.U. for Vitamin E is a measure of biological activity, not weight.

1 I.U. = 1mg standard dl alpha tocopherol acetate (the synthetic form). The natural d form is more biologically potent and 1mg d alpha tocopherol = 1.36 I.U. but bioactivity varies between different species.

Vitamin E is the most important fat soluble antioxidant which works with antioxidant enzymes to preserve and protect lipid cell membranes by neutralizing Reactive Oxygen Species ROS. It is able to be recharged by Vitamin C and continue its anti-oxidant function and is also important in regulating cell division and reproduction.

Most feeds naturally contain some vitamin E, but the levels are highly variable and subject to deterioration by oxidation after harvesting. Good levels may be present in fresh forage, but these fall markedly and are often low in hay.

Requirements have been estimated for all classes of horses (NRC 2007) and these rise with the intensity of exercise. Studies on racehorses have demonstrated improved athletic performance when horses received 1000 mg/day supplemental Vitamin E in addition to their normal ration. Intake in the range 1.5mg to 5mg/kg bodyweight are required to maintain vitamin E status in horses in work (equivalent to 750mg to 2,500mg/day for a 500kg horse). Supplementing horses in hard work with between 500mg and 2500mg Vitamin E per day is therefore appropriate.

Deficiency disease: Nutritional Myopathy or White Muscle Disease in foals is linked to both Vitamin E and Selenium deficiency and the treatment is supplementation with both selenium and vitamin E in high doses. The activity of some biochemical reactions of Vitamin E requires the presence of Selenium as a co factor, hence the two are interdependent to some extent.

There is little evidence that Vitamin E is involved in other muscle diseases like Tying Up or P.S.S.M. and it is unlikely that the vitamin will prevent either, though affected horses may benefit from supplementation for the antioxidant effects.

See also Selenium Se

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