So "Izzy" or Isn't He?

A week or so ago I wrote about Izzy's dramatically changing coat color. In that post I posited that he might have the cream dilution gene. Several people wrote to me privately expressing their doubts about that theory. Instead of a genetic cause, it was suggested, and not for the first time, that Izzy might have some mineral deficiencies, specifically copper and zinc. So it seems that there are three possible explanations.

From this color in April ...

 First, it just might be how he is. He's dark in the winter and fades in the summer. Gray horses undergo coat color changes all the time. What do they say about Occam's razor? The simplest explanation is most likely the right one. But not always. 

Second, he might have the cream dilution gene. In Izzy's pedigree, neither the Thoroughbred side nor the Oldenburg/Anglo-Arabian side recognize the color "buckskin." Instead, the Jockey Club recognizes Thoroughbreds as being either bay, black, chestnut, dark bay/brown, gray/roan, palomino (which carries two copies of the cream gene) or white. The Oldenburg Registry of North America recognizes brown, black, chestnut, gray, and bay horses. My research, limited as it was, says that on a black or dark bay/brown horse, the cream dilution gene can produce a buckskin, a sooty black, or simply a lighter brown horse with black points. In other words, without a genetic test, you can't tell just by "looking."

To this color in August.

That leaves the third option; Izzy might have a copper and zinc deficiency. Again, my research consisted of skimming articles found by doing a Google search. What I saw was that zinc deficiencies are rare. Over consumption on the other hand can decrease copper absorption. Some of the processes that copper is required for are energy production, iron metabolism, connective tissue formation, central nervous system function, and melanin production. Coat color is determined by the presence and proportion of melanin pigments.

Most of the articles I read warned against supplementing just with copper and zinc as that combination can negatively interact with other minerals in the body. Instead, it was recommended that horses with suspected copper and zinc deficiencies be fed a commercially fortified feed or a good mineral supplement. I've done both (Platinum Performance and Horse Guard) over the years for long stretches of time, but Izzy's coat still changes colors. He either doesn't have a zinc and copper deficiency, or, the supplements weren't enough to overcome the deficiency.

Izzy's Genetic Test

I am not worried about a copper and zinc deficiency, and it doesn't matter whether Izzy does or doesn't have the cream dilution gene, but I decided to find out for sure. UC Davis has a Veterinary Genetics Lab that is "open" to the public. They offer a long list of genetic tests, most of which seemed quite cheap. You can check for just about anything. For $25, I will know definitively if Izzy has the cream dilution gene or not. 

Earlier this week, I pulled the requisite mane hairs, ensuring that the root bulbs were attached. I taped them to the form as directed and dropped the whole thing in Monday's mail. The results should be back in a week or two. Either way, I know I should put both horses back on the Horse Guard Vitamin and Mineral Supplement. It won't hurt, and it probably helps their overall health.

Every time I try to keep things simple, I add in yet another thing.