Vitamin E is an important part of Equine nutrition, it is an essential vitamin and most horses are deficient in vitamin E because most horses don't have access to good pasture for 8+ hours daily and vitamin E in hay declines very quickly after drying (1-2 days).
Vitamin E in the ORGANIC form is better absorbed than in-organic. I give my horse Natural E Human capsules, the capsules also have soybean oil as a carrier which is GOOD because vitamin e is a fat soluable vitamin meaning it has to have a fat sourse to be absorbed fully. VERY CONVENIENT.
My horse who has no neuro issues that I know of gets 3-5 1000iu capsules daily. For a horse with EPM, he should be getting 12-20 1000 iu capsules daily.
Vitamin E deficiency has been shown to increase the chance of neurological disorders as EPM.
Good luck! :)
Edited to add: my horse now eats the capsules right from my hand! Which is even more convenient.