Scientists in Sweden announced an important discovery that helps explain how some horses are limited to “natural” gaits, while others are capable of additional gaits.

Nearly all horses use “natural” gaits (walk, trot, canter and gallop) without special training. Additional “ambling” gaits may occur naturally in some individuals, but usually only in certain breeds.

Researchers have identified a single gene mutation that enables horses to perform gaits such as running walk and pacing. The pace is a lateral two-beat gait; the two legs on the same side of the horse move forward together, unlike the trot, in which the two legs diagonally opposite each other move forward together. Not only does the mutation play a crucial role in the horse’s ability to perform “ambling” gaits, it also affects performance in harness racing. A report of the work has been published in the journal Nature.

Leif Andersson and his research team  in the Department of Animal Breeding and Genetics, at the Swedish University of Agricultural Science were looking for a genetic basis for gaits in horses. Only some horses can pace, and they wanted to find out why.

They studied the genomes of 70 Icelandic horses that could perform extra gaits — 40 could pace and 30 could perform other alternate gaits. They found that a single mutation in a gene called DMRT3 was strongly associated with the ability to pace. The mutation resulted in the production of a shortened form of the DMRT3 protein. Both copies of the gene were mutated in the pacing horses.

Andersson explained that horses without this mutation cannot move their right hindleg and right foreleg forward at the same time. But with the mutation the movement is not regulated so strictly and becomes more flexible. 

“We suspected a strong genetic component, but were almost shocked when we discovered that a single gene, DMRT3, largely explained the genetic difference between pacers and non-pacers,”  says Lisa Andersson, one of the Ph.D. students involved in the project.

The researchers developed a diagnostic test and found that the mutation is widespread among horses that show alternate gaits such as the Tennessee Walking Horse from the United States and the Paso Fino from South America.