Horses – DNA test by range of gaits on Icelandic horses can quest to fix human spine injuries.
Researchers have discovered a mutation in a single gene in horses that is critical for the ability to perform ambling gaits, for pacing and that has a major effect on performance in harness racing. The study, which is published in Nature today, is a breakthrough for our understanding of spinal cord neuronal circuitry and its control of locomotion in vertebrates.
Scientists said they had identified a genetic variant that influences gait in horses, a potential boon for breeders but also for the quest to fix human spine injuries.
A patented DNA test will become available from Thursday, enabling horse buyers to spot an animal with a higher genetic chance of success at harness racing, they said.
Reporting in the journal Nature, researchers in Sweden said the telltale gene had been unearthed in the Icelandic Horse, a breed that famously likes to “pace.”
Pacing is a peculiar kind of equine gait, in which the legs on one side of the animal move forward at the same time.
It is particularly prominent among Icelandic horses, descendants of horses introduced to Iceland by the Vikings and recognized as a purebred strain that gives a smooth, sure-footed ride.
Building on earlier work on lab mice, a team led by Leif Andersson at Uppsala University and the Swedish University of Agricultural Sciences compared the genetic code of 70 horses — 40 that could pace and 30 that could not.What emerged starkly was that in the 40 pacing horses, there was a tiny change, of just one letter in the code, in a key gene known as DMRT3.
DMRT3 controls a protein in nerve cells in the spinal cord that, Andersson believes, is crucial in the coordination of leg movements in vertebrates.
Just as surprising, said Andersson, was to find that the mutation also occurs strongly among trotters, or breeds that are used for harness racing, in which the horse pulls a two-wheeled buggy called a sulky.
Trotters have a gait that is diagonal, meaning that the rear leg and foreleg that are diagonally opposite to each other move at the same time.
In trotting races, a horse is not allowed to gallop, otherwise it is disqualified.
“What we think this mutation is doing is that it inhibits the transition to the gallop,” Andersson said. “That has some obvious applications in horse breeding.”
The genetic variant is widely spread among a breed called the American Trotter, but is found far less frequently among a rival called the French Trotter, he said.
“French Trotters are famous for being often very strong, but they are also famous for sometimes having problems in keeping the trot. They don’t keep a clean trot as much as American Trotters do, and we think the reason is that the breed does not have as high a frequency of the mutation.”
The team have patented the discovery and, from Thursday, licensed laboratories will be able carry out a test to scan a trotter’s genome for the DMRT3 variant.
Andersson said it was likely that further work would turn up other variants that influence horses’ gait, but for pacing and trotting horses, the DMRT3 mutation was clearly of enormous importance.
“It’s an important discovery also for human medicine,” Andersson said, referring to fundamental research into paralysis. “It is a really critical discovery because we have found new basic knowledge about how the spinal cord controls the movement of the legs.”
The Icelandic horses
The Icelandic horses is a breed of horse developed in Iceland. Although the horses are small, at times pony-sized, most registries for the Icelandic refer to it as a horse. Icelandic horses are long-lived and hardy. In their native country they have few diseases; Icelandic law prevents horses from being imported into the country and exported animals are not allowed to return. The Icelandic displays two gaits in addition to the typical walk, trot, and canter/gallop commonly displayed by other breeds. The only breed of horse in Iceland, they are also popular internationally, and sizable populations exist in Europe and North America. The breed is still used for traditional farm work in its native country, as well as for leisure, showing, and racing.
Developed from ponies taken to Iceland by Scandinavian settlers in the 9th and 10th centuries, the breed is mentioned in literature and historical records throughout Icelandic history; the first reference to a named horse appears in the 12th century. Horses were venerated in Norse mythology, a custom brought to Iceland by the country’s earliest settlers. Selective breeding over the centuries has developed the breed into its current form. Natural selection has also played a role, as the harsh Icelandic climate eliminated many horses through cold and starvation. In the 1780s, much of the breed was wiped out in the aftermath of a volcanic eruption. The first breed society for the Icelandic horse was created in Iceland in 1904, and today the breed is represented by organizations in 19 different nations, organized under a parent association, the International Federation of Icelandic Horse Associations.
The Icelandic horses is a “five-gaited” breed, known for its sure-footedness and ability to cross rough terrain. As well as the typical gaits of walk, trot, and canter/gallop, the breed is noted for its ability to perform two additional gaits. Although most horse experts consider the canter and gallop to be separate gaits, on the basis of a small variation in the footfall pattern,Icelandic breed registries consider the canter and gallop one gait, hence the term “five-gaited”.
The first additional gait is a four-beat lateral ambling gait known as the tölt. This is known for its explosive acceleration and speed; it is also comfortable and ground-covering. There is considerable variation in style within the gait, and thus the tölt is variously compared to similar lateral gaits such as the rack of the Saddlebred, the largo of the Paso Fino, or the running walk of the Tennessee Walking Horse. Like all lateral ambling gaits, the footfall pattern is the same as the walk (left hind, left front, right hind, right front), but differs from the walk in that it can be performed at a range of speeds, from the speed of a typical fast walk up to the speed of a normal canter. Some Icelandic horses prefer to tölt, while others horses prefer to trot; correct training can improve weak gaits, but the tölt is a natural gait present from birth. There are two varieties of the tölt that are considered incorrect by breeders. The first is an uneven gait called a “Pig’s Pace” or “Piggy-pace” that is closer to a two-beat pace than a four-beat amble. The second is called a Valhopp and is a tölt and canter combination most often seen in untrained young horses or horses that mix their gaits. Both varieties are normally uncomfortable to ride.
The breed also performs a pace called a skeið, flugskeið or “flying pace”. It is used in pacing races, and is fast and smooth,with some horses able to reach up to 30 miles per hour (48 km/h).Not all Icelandic horses can perform this gait; animals that perform both the tölt and the flying pace in addition to the traditional gaits are considered the best of the breed. The flying pace is a two-beat lateral gait with a moment of suspension between footfalls; each side has both feet land almost simultaneously (left hind and left front, suspension, right hind and right front). It is meant to be performed by well-trained and balanced horses with skilled riders. It is not a gait used for long-distance travel. A slow pace is uncomfortable for the rider and is not encouraged when training the horse to perform the gait. Although most pacing horses are raced in harness using sulkies, in Iceland horses are raced while ridden.
Please enjoy the video below which shows these range of gaits by Icelandic horses.
You can read about the DNA test from here