Vitamin E Deficiency Causes Rare Neurological Disorder

Grazing is a great preventive, but horses on hay-only diets may be at risk of Equine Motor Neuron Disease, or EMND.

Horse specialists at Casenovia College in New York are urging horse owners to have their hay analyzed for vitamin E content as well as other essential nutrients. The college lost a horse to a rare disorder called Equine Motor Neuron Disease (EMND) caused by a lack of vitamin E in the diet. When the college herd was tested, low blood levels of vitamin E were noted among the 70 horses.

EMND was first diagnosed in 1990. Classified as an “oxidative disorder,” it affects motor neurons in the spinal cord and impacts the horse’s nervous and muscular systems. Symptoms often mirror other neurological diseases such as West Nile virus, equine protozoal myelitis (EPM) and equine encephalitis. Symptoms may include:

• Incoordination
• Rapid weight loss (often despite a hearty appetite)
• Muscle wasting, weakness and trembling
• A tendency to lie down frequently
• Constant weight-shifting from one hind limb to the other
• Inability to carry the head and neck in a normal position

More than 10 years after the disease was discovered, researchers at Cornell University were able to link the disorder to vitamin E deficiency. Almost all the affected horses in the Cornell study had been off pasture for extended periods.

While fresh forage is generally high in vitamin E, hay may lose a certain percentage of this highly effective antioxidant dur- ing harvest and storage.

In many horsekeeping environments, hay, rather than pasture, tends to be the dominant component of the equine diet. The only way to ensure the nutritional value of that hay is to have it tested.

While most labs routinely evaluate hay for fiber, protein and minerals, Carol Buckhout, a Casenovia College assistant professor of equine business management, says owners should request specific testing to include vitamin E. This option is available through Equi-analytical Laboratories, which the college uses. By identifying a deficiency, the horse’s ration can be balanced and supplemented as needed.

In the case of vitamin E, an ounce of prevention is worth more than a pound of cure. Once damage has occurred to the horse’s nervous and muscular systems, complete recovery is unlikely-even when dietary balance is restored. So, if you are still feeding hay that has been stored over the winter, it would be wise to have it tested. And as you begin to purchase new hay this summer and fall, be sure to have that tested as well. For more information, log on to

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