Gene Mutation: No Performance Effect in Coldblooded Trotters

Gene Mutation: No Performance Effect in Coldblooded Trotters

The coldblooded trotter is truly a heavy horse. It’s one of two remaining breeds descending from the historic North-Swedish horse.

Photo: Courtesy Robert Fegraeus

The “Gaitkeeper” gene mutation might make a Standardbred more likely to win a trot race. But new study results have revealed that it doesn’t have the same effect on coldblooded trotters.

And that’s good news for an industry in which only 12% of the horses carry both copies of the DMRT3 (Gaitkeeper) gene, said Kim Jäderkvist Fegraeus, PhD, of the Swedish University of Agricultural Sciences’ Department of Animal Breeding and Genetics, in Uppsala.

Most successful Standardbred racehorses are homozygous, or “AA”—meaning they received a copy of the Gaitkeeper gene from both parents, compared to the heterozygous “CA” (only one copy) or “CC” (no copies), Fegraeus said. Coldblooded trotters, however, comprise a minority representation of AA horses.

Coldblooded AA horses in their study did appear to be faster in their early careers, while CC horses had a harder time keeping a clean trot, she said. But the AA horses had fewer starts and raced less frequently than CC and CA horses.

“If AA coldblooded trotters were truly ‘better’ racehorses, we probably would have observed a bigger difference between the genotypes for the various performance traits we investigated,” said Fegraeus. “For example, when looking at earnings, the CA horses actually earned more money on average than the AA horses. We would also expect the frequency of the AA genotype in the population to be higher, given the selection for performance.”

In their study, Fegraeus and her fellow researchers genotyped 769 coldblooded trotters (485 raced and 284 unraced) for the DMRT3 mutation. They then investigated 13 performance traits (related to rankings, racing times, earnings, disqualifications, and estimated breeding values) at three age intervals: 3 years old, 3 to 6 years old, and 7 to 10 years old.

Their statistical analyses revealed few significant associations between the Gaitkeeper gene and performance at a young age, Fegraeus said. In fact, very few of the AA horses (which made up 12% of the total study population) raced at all.

“It’s possible that the AA coldblooded trotters show early potential and are pushed too hard too soon, thus resulting in injuries,” she said. “However, it is also possible that AA coldblooded trotters prefer to pace, which would be detrimental to their harness racing career. At this time we really don´t know but we are currently investigating this further.”

Ultimately, Fegraeus said, “this is good news for the coldblooded trotter breed. As our results indicate that CA horses overall perform the best, this means that both CC and AA horses are needed for breeding. This decreases the risk for very intensive selection of a specific genotype. Too intensive selection for just one genotype can lead to an increase in inbreeding and lower genetic variation.

“Also, the study shows that all coldblooded trotters, regardless of DMRT3 genotype, can potentially become elite horses given an ideal environment,” she continued.

Unlike the Standardbred, the coldblooded trotter is truly a heavy horse, Fegraeus explained. It’s one of two remaining breeds descending from the historic North-Swedish horse.

“Coldblooded trotters are actually more genetically similar to the North-Swedish draught horse than they are to Standardbreds,” she said. “So coldblooded trotters and Standardbreds look rather different. Unlike many other racing breeds, the breeding goals of coldblooded trotters highly emphasize maintaining ‘type’ as well as improved performance.”

The study, “Lack of significant associations with early career performance suggest no link between the DMRT3 ‘Gait Keeper’ mutation and precocity in Coldblooded trotters,” was published in PLoS One

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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