The Irony with Gray Horses

27 February 2012
Posted in Articles

With horse people and non-horse people alike, gray is one of the most popular coat colors. Perhaps this is because it seems to hide conformational faults and can make a plain head appear beautiful. The irony is that gray is often an undesirable gene for breeders of white-patterned horses because the contrasting darker color gradually fades away. Because the gray (G) gene is dominant over all the genes discussed so far, it will eventually turn all other coat colors—dun, roan, bay, black, buck- skin, champagne, dun, palomino, roan and sorrel—white.

However, the gray gene does not affect the white hair on the horse’s body that is created by Paint Horse pattern genes, such as tobiano or overo, or white that occurs as a blaze, stocking or other mark- ing. These white markings remain visible even as the gray horse becomes whiter- looking with age.

Because gray horses do become whiter with age, they are sometimes confused with the white horse. The difference is that a mature gray horse may appear white, but has dark eyes and dark skin. A white horse also has dark eyes but has pink skin.

Gray horses are born with a colored coat such as black, bay, sorrel, dun, etc. Their foal coat typically reflects the base coat color, which the gray gene eventually turns white. A gray foal can sometimes be determined by white rings in their hair coats and around their eyes. This is often the beginning of the graying process, which varies from horse to horse. The graying process may occur over several years or a lifetime. The tail of a gray horse may also become whiter or remain dark.

In addition to its variable process, the gray gene creates many shades and patterns, including primitive markings, dapples (round, shaded spots) and “fleabitten” coats (flecks of color dispersed throughout the body). It is still unknown which genes control the shades and patterns of grays and the speed of the graying process. Therefore, the idea that a homozygous gray (GG) will turn white faster than a heterozygous gray (Gg) is unproven.

What is known is that homozygous grays do exist and they produce gray offspring 100 percent of the time. Heterozygous grays produce gray foals 50 percent of the time.

Unfortunately, both homozygous and heterozygous grays are prone to melanomas (skin tumors). These tumors commonly occur beneath a gray horse’s tail and around its ears. Fortunately, though they can be unsightly and disfiguring, only about 5 percent of these melanomas are malignant.

White Horses
In most breeds, including Paint Horses, true white horses are rare. Keeping this in mind, it may seem unusual to learn that the white gene (W) is dominant over all other coat colors, including gray. This means that any foal receiving one dominant white gene will be white.

White foals are born white and have dark eyes and pink skin, which eventually distin- guish them from a gray horse. If they have a Paint Horse coat pattern, it is not identifiable because the markings blend in with their hair coat, unlike perlinos and cremellos, which have visible patterns and blue eyes.

APHA has included the white color on its registration form for some time. ApHC and the Jockey Club also list white as a registerable color, but it is extremely rare in both breeds.