Vitamin E is a group of eight fat soluble compounds consisting of tocopherols and tocotrienols. They are essential for a variety of processes including energy metabolism, breeding & reproduction, support for the neuromuscular system & for protection against oxidative damage by free radicals.
Horses’ primary source of Vitamin E is leafy green forage, as d-α (alpha) tocopherol. This is not always sufficient and has be to supplemented in winter, for breeding, performance, & to support horses suffering from Cushings’ disease, polysaccharide storage myopathy & other nerve system disorders.
The most common form of vitamin E added to animal feeds is synthetic dl-α-tocopherol acetate. This consists of the d-form (isomer) and l-form in equal proportion. The molecular structure of these is such that they are mirror images. The l-isomer is not used at all & rapidly excreted. Trials have shown that the natural form is used more efficiently than the synthetic, with results varying from as much as x2 to x5 more effective.
A more recent development has been the introduction of a water-dispersible form of pure vitamin E, which has no other molecules. e.g. acetate attached. Whilst much more expensive, it is reported to be more effective for severer PSSM cases than the acetate form – see Pagan et.al. below.
Considerable research has been done around the world, in particular in the U.S.A at MSU—Michigan State University – & K.E.R – Kentucky Equine Research Institute. In a paper by its president, J.D. Pagan, plus M. Lennox, L. Perry, L. Wood, L.J. Martin, C. Whitehouse and J. Lange it was stated: “Natural-source water-dispersible forms of vitamin E were 5-6 times more bioavailable than synthetic vitamin E acetate, and a 5000-IU dose more than doubled serum vitamin E levels within 12 hr. These forms of vitamin E should be beneficial when a rapid increase in vitamin E is warranted such as during periods of oxidative stress (exercise or parturition) or for horses at risk of certain types of neurological disease.”
On the other hand in an article on September 5, 2019 By Stephanie Valberg, D.V.M., Ph.D., and Carrie Finno, D.V.M., Ph.D. they stated that natural vitamin E is largely twice as effective as synthetic.
They also added a note of caution: whilst an excessive level of vitamin E is not toxic (10 times the National Research Council recommendation), it is potentially detrimental to beta-carotene ( Vitamin A) absorption, and this high dose was not recommended.
For practical purposes it can be taken that the natural powder form is at least twice as effective as the synthetic, & the water-dispersed liquid perhaps twice that.
See Gravenhorse Feeds for supplies.
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