Imagine the scenario: A horse owner breeds her bright bay mare to a dark bay stallion, hoping for another flashy bay to shine in the show ring. Instead, out pops a chestnut foal. The owner wonders, ‘How did this happen?’ The answer lies in coat color genetics.

At the 2013 University of Kentucky (UK) Equine Showcase, held Jan. 18 in Lexington, Ky., Kathryn Graves, PhD, the director of the UK Animal Genetic Testing and Research Laboratory, reviewed the basics of equine coat color genetics.

Why should the average horse owner care about the genetics behind their horse’s coat color? Graves explained that some breed registries are either based on horses’ coat colors or have color restrictions. For instance, The American Paint Horse Association, the Appaloosa Horse Club, and the International Buckskin Horse Association, among others, are all color breed organizations, she said. On the other end of the spectrum, some groups like the Friesian Horse Association of North America and the Kentucky Mountain Saddle Horse Association won’t allow horses to be registered if they have certain amounts of white patches, she said. Graves also said that some horsemen believe horses of certain coat colors are easier to market and sell than others. Some owners even opt to have genetic tests run on horses to identify their genotypes (the genetic makeup of a given physical trait), especially if the animals will be used for breeding.

The completion of the equine genome in 2007 opened a door for geneticists to identify mutations for the basic coat colors, as well as modifying genes for other coat colors and spotting patterns, Graves said. In some c