Vitamins and minerals are the building blocks of healthy bones, muscles, and nerves, and deficiencies can compromise a variety of important bodily functions. For example, researchers know that an α-tocopherol (a component of vitamin E) deficiency can lead to significant neurologic problems. But they’ve also recently confirmed it can lead to issues in the horse’s eye, specifically the retina (the light-sensitive layer at the back of the eyeball that essentially connects the optic nerve to the brain, where a visual image is formed).

Prolonged α-tocopherol shortages contribute to the development of neuroaxonal dystrophy/equine degenerative myeloencephalopathy (NAD/EDM) and equine motor neuron disease (EMND). The former condition affects young horses and most commonly manifests as incoordination. On the other hand, EMND affects older horses and signs of disease include motor weakness (muscle wasting, trembling, and lying down more than normal).

“As veterinarians, we were always trained that these were two distinct diseases,” said Carrie Finno, DVM, PhD, Dipl. ACVIM, assistant professor and researcher of Population Health and Reproduction at the University of California, Davis, School of Veterinary Medicine.

However, results from a recent study by Finno and colleagues indicate these two maladies are likely connected, and affected horses require higher than normal amounts of