Vitamin E

What it does

Vitamin E and selenium together prevent nutritional muscular dystrophy, equine degenerative myeloencephalopathy and equine motor neuron disease ^[1].

Who is at risk

Deficiency is most likely in foals nursing mares on dry winter pasture, and in horses fed low-quality hay without supplements ^[1]. Horses in prolonged aerobic work, or on rations above 5% fat, may need more ^[1].

Excess

The MSD Veterinary Manual advises avoiding very high daily intakes in healthy horses ^[1].

Natural and synthetic forms

Natural vitamin E is more bioavailable than synthetic. One IU of natural vitamin E corresponds to about 0.67 mg of alpha-tocopherol, and one IU of synthetic to about 0.45 mg ^[1].

Reading it on a label

Labels may state vitamin E in IU or in mg. To convert mg to IU you need to know the form, because the factor differs between natural and synthetic vitamin E ^[1].

See also selenium, crude fat, reading feed labels.