Horses on fresh pasture have plenty of vitamin E intake, but not when the grasses die in the fall and winter.

EMND, or equine motor neuron disease, is a progressive degeneration of the nerves supplying muscle. It can result in mild elevations of muscle enzymes, progressive muscle atrophy with gait changes, weakness, tremors, severe weight loss and eventual euthanasia in horses. Some horses show at least a partial or temporary response to high-dose vitamin E supplementation and low vitamin E levels are commonly found. Until now, it was not clear if the vitamin E levels were an actual cause or a response to some other factor that increased the horse’s requirements for vitamin E.

A study just published in Acta Vet Scandinavia put 11 horses on a vitamin E-deficient diet. The intake levels of other antioxidant vitamins and enzyme systems in the blood were monitored. Control horses received the same diet and management, but with adequate vitamin E. By 44 months into the study, 10 of 11 horses had developed vitamin E deficiency by blood levels and EMND. None of the controls developed EMND. This study proved for the first time that vitamin E deficiency is a specific risk factor for the development of EMND.

Horses on pasture have adequate vitamin E for maintenance, but levels in hay and grain are very low. Many commercial grains have some E fortification, but often at levels too low to meet actual requirements. We recommend your horse receive 1250 to 1500 IU/day vitamin E for maintenance and at least 2000 IU/day for exercised horses not on pasture.