Why Your Horse Needs Vitamin E

Did you know that many of the horses in Alberta are deficient in Vitamin E?

The major dietary source of Vitamin E for horses is forage, and more specifically, pasture.  But did you know that vitamin E starts to oxidize as soon as hay is cut?  This means that many horses are not getting an adequate amount of vitamin E from hay alone.  In order to get adequate vitamin E, most horses need to be grazing for 12 hours per day at least 6 months out of the year.  For many horses in our area, this isn’t an option as they are either stalled or there isn’t an adequate amount of pasture for them to graze on for this long.

Why is Vitamin E important for my horse?

While it has a role in many functions in the body, Vitamin E is especially important for keeping a horse’s muscles and nerves working properly.  Inadequate levels can have profound effects on a horse’s neuromuscular system and can have varying effects depending on the age of the horses and the length of time they have been eating a diet deficient in Vitamin E.  In middle aged horses, a lack of vitamin E can contribute to the development of Vitamin E deficient myopathies (a disease that affects muscles that control movement resulting in weakness and muscle malfunction).  Younger horses that are raised in a Vitamin E deficient environment or who are born to mares fed a diet deficient in vitamin E are prone to Equine Neuroaxonal Dystrophy (eNAD) or Equine Degenerative Myopathies (EDM), which are a result of severe abnormalities of neurons in the brain and spinal cord.  Older horses that have been deficient in Vitamin E for some time can develop Equine Motor Neuron Disease (EMND), a disease that causes weakness and muscle loss due to dysfunction of the nerves that supply muscles throughout the body.  In performance horses, we can see subtle performance deficits (like trouble with lead changes for example) or concerns with poor performance as the earliest indicator of muscle dysfunction from a lack of Vitamin E.  

How do I know if my horse has adequate vitamin E levels?

Testing Vitamin E is relatively simple and requires one blood draw that your veterinarian sends to the lab for analysis.  The test is quite economical and provides you with valuable information about your horse’s health.  Horses are considered deficient in Vitamin E if their serum concentration is less than 2ug/mL.

What can I do about it if my horse is deficient in Vitamin E?

Depending on how severe the deficiency is, horses are either started on liquid or powdered form of natural vitamin E (alpha-tocopherol).  Synthetic vitamin E is not as bioavailable to horses (meaning they can’t absorb it well), which makes it a poor choice for horses.  Unfortunately, this is commonly found in many supplements on the shelf because it is cheaper, so it’s important that you know what you are looking for.  Your veterinarian can help you choose which product is most appropriate for your horse based on their test results.

Give us a call if you’d like to find out your horse’s vitamin E levels!

***This information is a summary of the 2024 AAEP Convention presentation by Dr. Carrie Finno, DVM, PhD, DACVIM who is a professor at the Davis School of Veterinary Medicine at the University of California.