Q. My horse has developed white pigmentation around one of his eyes. A friend mentioned that this might be due to a copper deficiency. Is that true?
A. Vitiligo is a skin condition that’s essentially cosmetic in horses. It occurs in other mammals, including dogs, pigs, and people, and is an autoimmune condition that targets and kills the melanocytes in the skin.
Melanocytes are the skin’s pigment-forming cells, so when they die the skin becomes white or unpigmented. Although first described about 3,500 years ago in people, vitiligo wasn’t mentioned in scientific literature about horses until 1931, and multiple scientific reports didn’t occur until the 1960s.
The condition occurs in several horse breeds and is thought to be particularly common in Arabians. In fact, it is referred to as “Arabian fading syndrome” or “pinky syndrome” in that breed. However, with limited published literature on the condition, it’s possible that vitiligo is just as prevalent in other breeds but not formally recognized. The depigmented areas might not be permanent, and in some horses vitiligo comes and goes. Stress might trigger its appearance.
Doctors have tried a number of treatments for people with vitiligo with varying results, but researchers have not tested most of these treatments for efficacy in horses. Very limited studies in horses (11 horses total) have indicated nutritional changes might help. Supplementing vitamins A, D, E, and B12 caused complete repigmentation in one horse, while in another report supplementing with high levels of chelated copper helped. However, when the supplemental copper was reduced after five months, the vitiligo returned. After copper was again increased, depigmentation was reduced. It’s possible that in this case the issue was a copper deficiency not autoimmune-induced vitiligo.
While diet might not be implicated in your horse’s case, exploring possible nutritional deficiencies and correcting them will support his overall health and well-being. Copper is a mineral often lacking in forage-based diets. So, if your horse is only consuming pasture or hay, he is likely deficient in copper as well as other important nutrients such as zinc. He might also be deficient in copper if you’re giving unfortified supplemental feed (such as grains, hay pellets, and/or beet pulp rather than concentrates or complete feeds).
Giving your horse fortified feeds and following feeding directions by measuring the correct amount for your horse’s body weight and work level will ensure he gets the nutrition he needs. Commercially fortified feeds should also provide supportive amounts of vitamins, although possibly not enough vitamin E—meeting your horse’s vitamin E needs might require additional supplementation.
If the depigmented skin remains, protect it from excessive sun exposure, as depigmented skin can burn. Use a good barrier sunscreen and a UV-protectant fly mask.