Vitamin E In Horses
Vitamin E functions as a biological antioxidant that serves to maintain normal neuromuscular function. Equine diseases that develop in the face of vitamin E deficiency in young animals include nutritional myodegeneration in conjuction with selenium deficiency, equine neuroaxonal dystrophy (eNAD), and equine degenerative myeloencephalopathy (EDM). Adult horses deficient in vitamin E may develop a vitamin E deficient myopathy or equine motor neuron disease (EMND).
Naturally, horses obtain sufficient amounts of vitamin E through lush green pasture. However, this is not a realistic option for all horse owners. Another option to increase vitamin E levels in a deficit animal is through supplementation. Most vitamin E supplements consist of natural forms of alpha-tocopherol because alpha-tocopherol is the most biologically available and well researched isoform of vitamin E. The most efficient way to rapidly increase levels is to administer a natural water-soluble Emcell Stuart Product supplement (Elevate W.S. or Nano-e). Powdered options are widely available and increase levels over a longer period of time. It is important to periodically check serum alpha-tocopherol concentrations and, if an adequate response to supplementation does not occur, the dose or formulation of alpha-tocopherol should be modified.
When a sample is evaluated, it is the concentration of alpha-tocopherol that is being measured. A blood sample using serum or plasma is the most readily available option for determination of α-tocopherol deficiency. Normal reference range concentrations of alpha-tocopherol in horse plasma and serum are:
>2 μg/mL Adequate
1.5-2 μg/mL Marginal
Only certain animals demonstrate clinical signs of neuromuscular disease even if the alpha-tocopherol deficiency exists in an entire herd of horses. Development of neuromuscular disease appears to depend upon the age of the animal when deficiency develops, the duration of alpha-tocopherol deficiency, the genetic make-up of the individual and other concurrent dietary deficiencies or excesses. In many horses, there are no apparent ill effects of an alpha-tocopherol deficiency. Therefore, a neuromuscular disorder requires signs of alpha-tocopherol deficiency and elimination of other possible diseases.
Current National Research Council (NRC) daily recommendations for vitamin E in horses are 1 -2 IU/kg body weight, however, these NRC recommendations do not discriminate between natural or synthetic sources. The NRC has set the upper safe diet concentration at 20 IU/kg BW based on biopotency of synthetic vitamin E (10,000 IU/500 kg horse). Above this level, coagulopathy and impaired bone mineralization have been reported. Furthermore, in healthy exercising horses, high dosage of vitamin E supplementation (10x NRC requirements) was shown to be potentially detrimental to absorption of certain nutrients and thus, is not recommended. Research-based evidence for the need for additional alpha-tocopherol supplementation above 500 IU/day is lacking in healthy young and middle-aged horses receiving adequate dietary vitamin E intake.
1. NRC. Nutrient Requirements of horses. 6 ed. Washington, D.C.: National Research Council, 2007.
2. Williams CA, Carlucci SA. Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses. Equine Vet J Suppl 2006:617-621.