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Vitamin E Deficiency in the Horse and Choosing a Vitamin E Supplement for Your Horse

Toby Pinn, DVM, DACVIM

                Low vitamin E levels in our equine patients often result in poor muscle development, muscle weakness, or a more severe neurologic condition called Equine Motor Neuron Disease (EMND).  Because our horses are intended to be athletes, we often monitor serum vitamin E levels and supplement where necessary to maintain and improve performance levels. In addition, vitamin E is an important anti-oxidant, and its supplementation is often recommended in our geriatric horses. Green forage such as fresh green grass, is the best natural source of vitamin E. Due to the shortened grazing season in our northern practice area, even those horses with access to unlimited pasture can become deficient in Vitamin E.  Although most grain is supplemented with vitamin E, the grain may contain less than the NRC daily requirements or may be fed at a decreased volume. Some horses are ‘easy keepers’ or have conditions that warrant limited access to green grass and grain (such as laminitis, Cushing’s Disease or Equine Metabolic Syndrome). These horses might be at higher risk for developing vitamin E deficiency if supplementation is not provided.

                The recommended daily amount of vitamin E consumed by your horse should be around 1000 international units (iu). When a horse is diagnosed as deficient based on a blood sample, we will often recommend very high daily levels, up to 10,000 iu daily to restore normal levels quickly. It often takes weeks to months after initiating supplementation to bring a deficient horse’s vitamin E levels back into the normal range.   Here is where things get a little complicated…

 As I’m sure most horse owners know, there is an overwhelming number of vitamin E supplements available through various catalogues and online distributers. When selecting a vitamin E supplement for your horse it is most important to try to select a product containing NATURAL vitamin E. Natural vitamin E is best absorbed and most effective. Here is the ‘need to know’ information:

  1. Make sure the supplement you choose is NATURAL vitamin E and not labeled as ‘synthetic ‘ or vitamin E ‘complex’.   Vitamin E ‘complex’ may contain only a small part natural vitamin E, and the rest synthetic. In addition, when a product is labeled as natural, be sure to look closely at the label, as this product still can contain some portion synthetic vitamin E. Tricky!!
  2. Look at the ingredient label, the chemical name for natural vitamin E is d-alpha-tocopheryl  or d-alpha-tocopherol.  Synthetic vitamin E has the letters ‘dl’ in front of the chemical name dl-alpha-tocopheryl or dl-alpha-tocopherol. 
  3. Human-grade vitamin E gel capsules are an inexpensive source of vitamin E, but are often low cost because they contain synthetic vitamin E. These human-grade supplements are not the best choice for your horse despite the low cost.

If you have questions regarding vitamin E deficiency in your horse, or regarding vitamin E supplementation in your horse, please contact the VLAC veterinarians.