In a recent article in The Practitioner, Drs. Carrie Finno and Stephanie Valberg discussed the disorders that are related to a deficiency of vitamin E in the horse. The article reviewed the role that vitamin E plays in the equine body (antioxidant and other yet-to-be-determined activities) to maintain normal neuromuscular function. If the horse is deficient in vitamin E, several specific equine diseases can develop. These include nutritional myodegeneration, neuroaxonal dystrophy, and equine degenerative myeloencephalopathy in young animals. Reference ranges were given for serum/plasma samples. Vitamin E deficiency can exist in an entire herd of horses, yet only a few may show clinical symptoms as development of the disease may depend on the age of the animal when the deficiency develops, the duration of the deficiency, the genetic make-up of the individual and any other dietary deficiencies/excesses that may also be present.
The article then reviewed the different diseases and ended with a discussion of vitamin E supplementation. It was emphasized that “the absorption and metabolism of vitamin E in healthy horses may differ from horses with vitamin E deficiency.” Which vitamin E supplement is chosen should differ depending on whether a maintenance supplement is needed for a horse with a normal α-tocopherol (the form of vitamin E that is measured in the blood sample) or a horse that is in need of a supplement to provide a rapid rise of α-tocopherol due to low blood levels and clinical symptoms of a deficiency. In healthy horses, the NRC daily recommendation for vitamin E is 1-2 IU/kg of body weight, but these recommendations do not consider what type of vitamin E is being fed. The NRC has also set an upper limit for vitamin E at 20 IU/kg body weight based on the potency of a synthetic vitamin E. Feeding above these levels (10,000 IU/day/500 kg horse) can result in coagulopathy (a condition in which the blood’s ability to clot is impaired) and impaired bone mineralization.
Article: Finno, CJ, Valberg, SJ. Disorders Related To Vitamin E Deficiency. The Practitioner, issue 4, 2015, pp 7-10.