Clara Mason, DVM

44 Cloverleaf Street
Winfield, WV 25213


Vitamin E supplementation in Horses deficient in Vitamin E 

Vitamin E is absolutely necessary in the horse.  It is a FAT soluble vitamin typically found in green forage.  Since it is a fat soluble vitamin vs a water soluble vitamin (Vitamin B, C) vitamin E can be over-dosed.  It is important that you follow a few guidelines to adequately and safely supplement your horse with vitamin E.
1.  What does Vitamin E do in the body?
Vitamin E is necessary for the well-being of the reproductive, neuromuscular, ocular (eyes) systems of the body and more importantly, it is a powerful antioxidant.  Deficiencies in young horses causes nervous system disorders.  In older horses, a deficiency of Vitamin E causes reproductive and muscular issues.
2.. Where do horses obtain Vitamin E naturally?
Vitamin E is found in very green grass.  Horses that are allowed to graze on green pastures will take in vitamin E daily.  Since Vitamin E is stored in the liver, most horses will make it through the winter without supplementation with this vitamin. It will take more than a year for the liver to exhaust its stored supply of Vitamin E.
3. What is a normal level of Vitamin E in the horse and how do you assay deficient Vitamin E levels in the horse?
Unfortunately, Vitamin E deficiency is not determined by one blood test.  Instead, to accurately determine if your horse is deficient, you must measure a few parameters including a serum test, a muscle biopsy and a clinical examination to determine if the horse is showing symptoms.  Normal serum levels in the horse is 2ug/ml.  (4ug/ml can be too high)
 4. How do I supplement Vitamin E in horses?
Vitamin E is supplied in two ways: natural and synthetic.  Natural comes in powder and liquid forms with the powder form more stable with a longer shelf-life, but is not absorbed as well as the liquid.  To determine if your Vitamin E is in the natural form, the label will list the vitamin as RRR alpha tocopherol. The synthetic form is not absorbed very well.  Therefore, using the NATURAL or RRR liquid form is preferred.
5.  Problems with supplementing Vitamin E
Not all horses respond to Vitamin E even if supplemented in the proper dose and RRR form.  The estimate is that only 60% of the horses will respond to the supplemented Vitamin E.  Injectable Vitamin E/selenium does not elevate the Vitamin E levels to acceptable doses due to absorption.
Supplement Vitamin E only if you have a deficiency that requires daily administration of Vitamin E and under the guidance of a veterinarian.  The best way to provide adequate levels of Vitamin E for horses is to allow grazing of green grass most of the year.