The myostatin gene (MSTN) has attracted the attention of many racehorse breeders for its association with racing performance. But new research has revealed that this muscle-fiber-building gene could also impact performance in other breeds. In fact, it might even affect gaited horses’ ability to perform the very gaits they’re known for.

“It requires a lot of strength and stamina to carry a heavy rider while simultaneously presenting a nice form on a breeding field test (for gaited horses),” said Liesbeth François, a visiting PhD student from the KU Leuven Livestock Genetics research group, in Belgium. “As such, by influencing the type of muscle fibers, MSTN likely supports a horse’s ability to perform gaits of a certain quality.”

For example, the Icelandic horse’s famous four-beat tölt might benefit from the right kinds of muscle fibers as determined by MSTN, said François. While researchers have recently identified the “gaitkeeper” gene as being primarily responsible for a horse’s ability to tölt, François said MSTN also appears to play a role—probably in the way it affects a horse’s muscular ability to carry out such a physically demanding movement.

In their study, François and colleagues genotyped three segments of the MSTN gene in 195 Icelandic horses. The horses were mainly from Iceland and born between 1968 and 2006. They had all undergone breeding evaluations, in which breed experts judged their morphology and gaits