Why vitamin E is critical for horses

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Why vitamin E is critical for horses
Peach (left) passed away unexpectedly as a result of vitamin E deficiency.

You’ve checked to make sure your horse is getting enough protein, fiber and fat in her diet – but what about vitamin E? Here’s why this micronutrient is so important.

My family learned through tragedy that many equine diets are lacking a basic nutrient: vitamin E. In the spring of 2016, one of our Quarter Horse mares had a filly named Peach. Although she appeared normal at birth, her neurologic health rapidly deteriorated. Veterinary diagnostics did not provide an answer, and no treatment options were discovered. The neurologic deficits quickly worsened, and it seemed there was nothing we could do to help. Peach was so unbalanced that she could barely trot or take a single step backwards.

Prior to Peach’s birth, an older horse on our farm had begun exhibiting muscle wasting and trembling. She was diagnosed with a ‘typical’ vitamin E deficiency and supplementation was recommended by the veterinarian. Unfortunately, due to differing symptoms, we did not make a connection between her diagnosis and Peach’s condition.

In our final, desperate, attempt to help Peach, we found research conducted by Dr. Carrie Finno at UC Davis. Due to her expertise in diagnosing and treating equine neurologic disease, she agreed to travel to our farm and conduct examinations.

She recommended serum vitamin E assessments, and the results were staggering. “A serum vitamin E assessments is a blood test that determines if a horse has low levels of serum alpha-tocopherol (vitamin E),” explains Dr. Finno. “Deficient horses are at risk for developing several neurodegenerative conditions, including equine neuroaxonal dystrophy (eNAD).” To our surprise, nearly every horse on our farm was critically low.

These horses were being fed high quality hay in combination with a fortified grain. But according to Dr. Finno, there’s no substitute for fresh green pasture, which is a primary source of vitamin E. Since vitamin E oxidizes once grass is baled into hay, it’s not a suitable substitute.

We immediately began supplementing all of our horses with natural vitamin E, but Dr. Finno thought that Peach might have eNAD. Unfortunately, post-mortem examination of the central nervous system would be the only way to know for sure. “eNAD develops in genetically predisposed horses that do not receive adequate dietary vitamin E during the first few years of life,” says Dr. Finno. “Peach’s clinical signs of ataxia (incoordination) were consistent with this signs associated with this disease. Additionally, Peach’s serum vitamin E concentration was low.”

We tried feeding Peach high doses of vitamin E, but her disease had progressed beyond repair. The only option was euthanasia. Necropsy at UC Davis confirmed that Peach had, in fact, suffered from eNAD. This disease could have been prevented by ensuring that Peach received adequate vitamin E throughout gestation and after birth. Her specific genetic predisposition, combined with a severe vitamin E deficiency early in life, meant she never had a chance. By the time we figured out what was wrong, all the supplements in the world couldn’t save her.

The older horse that was diagnosed with vitamin E deficient myopathy has made a full recovery. All the other deficient horses are also better than ever – lucky, considering every single one of them was at risk of severe health problems despite having no clinical signs. Horses that we (and our veterinarians) thought were 100% healthy, have better muscle condition and coat quality than ever before in their lives.

It just goes to show how unique every horse is, and how differently each individual body responds to adversity. It also drives home the fact that even horses without clinical signs may be severely deficient in this key nutrient.

“It is important to learn to recognize the signs of neurologic disease in horses,” says Dr. Finno. “These may include stumbling, incoordination, abnormally dull mentation, and a base-wide stance. A veterinarian should examine any horse demonstrating these clinical signs. Additionally, assessment of serum vitamin E concentrations is especially important in pregnant mares during late-term pregnancy and foals during the first year of life. If warranted, supplementation should be instituted.”

In memory of Peach, my family has made it our mission to spread vitamin E deficiency awareness. Consider working with your veterinarian to send a sample of your horse’s blood for analysis!