The Importance of Vitamin E


The Northwest and the Northeast are both areas that have soil deficient in vitamin E and selenium. This means that everything grown in the region is deficient as well. Broodmares, breeding stallions, newborns, growing horses, horses in training/work and older/retired horses have all been shown to have problems when vitamin E is not adequate – this is essentially all horses! When caught early a vitamin E deficiency can absolutely be corrected with proper supplementation. However, the deficiency can cause irreversible damage to foals (from deficient mares) and growing horses. And, adult horses can reach a “point of no return” when no amount of supplementation can reverse the clinical signs.

What does vitamin E do?

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Dr. Elizabeth Carothers

Vitamin E is a non-toxic fat soluble vitamin that acts as an antioxidant and free radical scavenger. This means that it decreases the damage caused by inflammation or stress to the tissues. These stressors can be as minor as sun exposure or as intense as an endurance competition. In the body’s daily war to maintain health and decrease the effects of these stressors, antioxidants like vitamin E are an important ground troop. Vitamin E is critical for a functioning immune system, nervous system, muscular system (skeletal and cardiac) and even the reproductive system. Vitamin E has separate but overlapping roles with selenium, although this article will just focus on vitamin E.



Where do horses get vitamin E?

The main source of vitamin E for many horses is green pasture. For horses that do not have grass turn out, or for the horses living in a deficient region like ours, this is a problem. Alfalfa hay and good quality grass hays can also be sources of vitamin E. However, vitamin E degrades quickly and has been shown to decrease by 30-80% just by the act of cutting and baling the hay! Even more vitamin E is lost during storage of the hay. Many supplements and feeds have low levels of vitamin E added because it is an expensive ingredient and because it is assumed that horses are getting vitamin E from their other food sources. So, you can see how a deficiency could happen!

How much vitamin E do horses need?

Recent research has indicated that horses need more vitamin E than we used to think. A general rule of thumb for maintenance is 1500IU a day for a 500 pound pony and 3000IU a day for a 1000 pound horse.

How do you know if vitamin E is low?

The effect of a low vitamin E depends on the age of the horse and other predisposing factors like genetics. But, some of the most common clinical signs are:

  • Lack of endurance
  • Poor performance
  • Muscle weakness – especially in the hind end  
  • Difficulty going up or down hill
  • Avoidance of work requiring hind end impulsion
  • Dry skin and hair coat
  • Frequent Illnesses
  • Decreased muscling
  • Cardiac abnormalities (especially in foals)
  • Stumbling, tripping or scuffing of the hooves
  • Reluctance to "square up"
  • ETC!

We can look for some of these signs on clinical exam – many of you have probably have seen Dr. DeWard or I checking hind end strength and tail tone for example. As the owner you can also provide critical information about their performance under saddle. However, all horses have a different way of manifesting a low vitamin E and checking blood levels by performing a vitamin/mineral panel can be key. In addition to vitamin E, a vitamin/mineral panel will also give values for selenium, calcium, phosphorus, magnesium, iron, zinc and copper. This can allow us to evaluate the diet more specifically and monitor change over time.

What happens if they do have a low vitamin E level?

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DRY LOT (no vitamin E)
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Dry Lot with vitamin E supplemented
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If we determine that a horse has a low vitamin E we will prescribe a course at a higher level of supplementation for 4-6 months before decreasing to a maintenance level. As a fat soluble vitamin it takes longer to increase and replenish the body’s stores. We will also monitor their clinical signs and titrate the supplement level to each horse.

What supplement should I use?

When choosing a supplement, look for one that is all (or mostly) a natural source of vitamin E which will be labeled as “d-alpha tocopherol”. Horses do not absorb the synthetic source well which will be labeled as “dl-alpha tocopherol”. Supplements we recommend commonly are Elevate WS (Kentucky Performance Products), E5000 (VitaFlex), Ultra Cruz natural vitamin E(Santa Cruz) or even the human capsules which can be squeezed on the feed or fed whole if the horse will eat them that way. There are many others though so definitely feel free to ask us to evaluate the labels for you. The world of horse supplements is a confusing one!

If you think any of these symptoms sound like your horse or if you have questions about your horse’s diet or supplements please call or discuss this at your next appointment. We want all our equine friends to be as happy and healthy as possible and vitamin E as part of a balanced diet is a critical part of that!

Article courtesy of Dr. Elizabeth Carothers