The color of the horse has been a topic of controversy and misunderstanding for as long as we have tried to put labels on colors. I have heard things from “It’s not black if it fades in the sun”, “palomino and flaxen chestnut are the same thing”, to “Pink skin and light blue eyes means albino”. Of course all of these statements are false and in this and the next few articles, I will discuss why.
With DNA color testing we can know for certainty what color our horse is. It is relatively cost effective and takes all the guess work out of labeling the color. But do we really need to test to know if our red horse is chestnut or our black horse is really black? Well yes, sometimes we really do.
There are only two colors of horses; red and black (red being chestnut). Every other color that you see horses come in is a result of another gene or group of genes being added to the base color. The bay gene (agouti) restricts black pigment to the points, making the bay color. There are actually three types of agouti. One produces the brown color, one the bay color and the last and the rarest is the wild bay. Sometimes the seal brown horse is so dark that when we look at it, it looks black. This is where a DNA test will show the presence of the agouti. For those of you who are unfamiliar with the term ‘wild bay’, wild bay is when the black pigment on the legs does not come above the knee/hock but only comes just above the fetlock. A horse can carry no agouti, one agouti or two agoutis, either the same or different (stating this in a simplified manner). This applies to chestnut horses as well. When you get a bay foal out of a chestnut mare bred to a black stallion, you know that the mare carries at least one agouti. Some black horses fade in the sun, and some black horses don’t fade in the sun. They are referred simply as fading and non-fading blacks. They don’t have to have an agouti to fade in the sun, but the seal brown horse definitely sun fades and shows more brown in the summer.
The chestnut horse is one of the most interesting. There are many genes added to the color that really shows up on chestnut that you don’t see on the black-based horse. The sooty gene darkens the mane and tail and the flaxen gene lightens the mane and tail. Of course the horse can have both genes. That’s an interesting look! UC Davis and other labs have done research on the flaxen gene but to my knowledge, we still can’t test for the sooty gene. The liver chestnut is also thought to be caused by a different gene. The chestnut horse can be so dark that it looks black, or so light that it looks orange. Genetically fascinating to me!
Morgan horses come in a variety of colors. Once it was thought that if it wasn’t black, bay or chestnut, it wasn’t a Morgan, some people still subscribe to this belief. While in the early years, Figure bred mares of all shapes and colors to produce what we all know to be the Morgan horse. I do believe that some of the colors were lost through selective breeding. The reintroduction of some of these colors was brought about by an outcross. A lot of these descendents still qualify as foundation bred. Some of these colors were never lost, they were just so rare that they were overlooked or thought to be something else. So in short, if they pass the DNA parentage test to be registered, they are indeed a Morgan.
In the next issues, I will discuss more of the dilution and modifying genes, dominant & recessive genes, heterozygous & homozygous genes and white markings and pinto patterns. I welcome all comments and questions. I hope to hear from you.