The Genetic Basics of Gait

A study was conducted that analyzed horses to determine whether there was a genetic variation with those that were known to exhibit intermediate gaits and those that did not. The conclusion was made that there is a mutation of the DMRT3 gene in horses that causes a horse to exhibit different ambling gaits. This mutation, when genetically tested, is denoted as an “A” when it appeared in the allele. Alleles that do not have this mutation are denoted as a “C.” Each horse inherits one of these alleles from each parent. A horse tested as “CC” (no mutation) does not have any copy of the genetic mutation, therefore their gaits are only Walk, Trot, Canter (WTC). A horse tested as “CA” (heterozygous) only has one copy of the mutation for ambling gaits. A horse tested as “AA” (homozygous) has two copies of the mutation.

So, what does this translate to when it comes to the horse exhibiting gait? Knowing these genetics only guarantees one thing- whether that mutation will or will not be passed on to offspring. There is a wide variation of type, speed, and quality of gait amongst those tested as heterozygous and homozygous. Some heterozygous horses could be more naturally “gaited” than a homozygous, and vice-versa. However, your best option if you want a naturally gaited horse will be to choose one that is tested as “AA,” but the eye test is as important as knowing the genetics of the horse.

What does this mean for a breeder? Breeders like us at Mary Mel Morgans who want gaited offspring will try to breed only “AA” horses. Of course, many other considerations are taken when we select breeding prospects such as overall conformation and whether the horse favors the trot or pace and pairing them up accordingly. But to put it simply, we strive to only breed “AA” horses to give a better probability that the horse will exhibit quality ambling gaits, as the offspring will always be “AA.”