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Vitamin E and the Neurologic Horse

Vit EFat soluble vitamins are important in equine nutrition, vitamins in this group are M, A, D, and E.  Fat soluble vitamins are important in cell membrane functions and immunity.  Vitamin E, also called alpha-tocopherol,  is unique because it isn’t involved in specific metabolic functions but it is the body’s major fat soluble antioxidant.  The action of the anti-oxidant vitamin is to prevent free radicals from destroying (though oxidation) fats in the body.

Vitamin E  is found in green grass, horses that are on pasture will get plenty of vitamin E in their diet. Because horses don’t make this vitamin it is called an essential daily nutrient.  Horses that may need supplementation include pregnant mares, mares with foals, young growing horses, and performance horses that do not have access to green pastures. Horses that are restricted from eating lush grass, horses with metabolic syndrome, are also at risk for inadequate levels. Vitamin E is a treatment for Equine Motor Neuron Disease (EMD) but has no effect in horses with Equine Degenerative Myeloencephalopathy (EDM).  Vitamin E is often suggested to enhance recovery of horses with Equine Protozoal Myeloencephalitis (EPM) although there are no studies to support this recommendation. You can read a little more about these rare diseases, EMD/EDM/EPM at

There are no cost-effective means of rapidly increasing serum and cerebrospinal fluid levels of alpha-tocopherol and then sustaining the concentrations; a recent report recommends a water-dispersible formulation followed by a gradual transition to the acetate form of Vitamin E over a 7 week period. This study also highlights the need for periodic evaluation of Vitamin E concentrations because responses vary among individuals.  There are plenty of reviews of supplements and amounts to use in each type of deficiency; the need for supplementation should be discussed with your veterinarian. Remember, supplements are not without risk, especially supplementing fat soluble vitamins. How much is too much and what does Vitamin E toxicity look like? In people an overdose can cause muscular weakness, fatigue, diarrhea and bleeding.  The possibility of bleeding is of the most concern in supplemented horses.

The good news is that Vitamin E is easily  measured in the blood.  The alpha-tocopherol levels are reported as micrograms per ml (µg/ml).  If a horse has more than 2 µg/ml the level is adequate.  If the range is between 1.5 –2 µg/ml the levels are marginal and if the levels are less than 1.5 µg/ml the horse is deficient. A blood level should be taken before supplementation, after 30 days and prior to discontinuing therapy.  If desired levels aren’t attained after 30 days a different formulation may work. Testing is less expensive that maintaining a horse on a needless supplement or overdosing a horse.

2 µg/ml Adequate, no supplementation needed
1.5 –2 µg/ml Marginal
<1.5 µg/ml Deficient

Pathogenes no longer offers testing Vitamin E levels in serum and CSF.