By recognizing and selecting for these genes, breeders could fine-tune their production techniques, which could lead to fewer unsuccessful racehorses that often end up removed from the racing industry. “Although slower than environmental interventions (such as changes in management and training), genetic changes are known to accumulate over generations and, thus, genetic research provides an avenue for more permanent change,” said Brandon Velie, BSc, MSc, PhD, of the Equine Genetics and Genomics Group at the University of Sydney.
Finding the Right Genes That Make the Right Proteins
Researchers had already narrowed their list to six genes they thought might contribute to Arabian racing success, Velie said. In the end, though, it seemed clear that one gene—SLC16A1—was strongly associated with racing success. And two other genes—ACOX1 and ACTN3—seemed very likely to be related.
Like all genes, these three code for protein production, meaning they have their own “recipe” for making proteins. Each one is only slightly different from the corresponding three genes in other (nonracing) Arabians, but the slight change in “recipe” could make all the difference, even if it only switches out a single “ingredient.” Depending on how it’s made, a protein can have a very different effect on the way the body functions—enough to distinguish the horses who win from those who don’t, Velie said.
In their study, Velie and his fellow researchers ran genotyping on 287 purebred Arabian horses born in Poland and having competed in a gallop (nonendurance) race at least once. They specifically analyzed the six genes that had been previously identified as possibly affecting performance, and they compared the genetic findings to racing data for each horse.
While three candidate genes (PLN, SH3RF2, and GPX1) didn’t seem to have any associations with racing performance, the other three clearly did, the researchers said.
SLC16A1, ACOX1, and ACTN3: Names To Remember for Racing Arabian Breeders
The clearest association between genes and racing performance came from the SLC16A1 gene, Velie said. The protein it codes for affects lactate production. Lactate accumulation is a byproduct of creating energy without oxygen (which complements energy created with the use of oxygen to give fast bursts of energy for short, intense exercise). But lactate that lingers in the muscle cells causes soreness and fatigue, leading to reduced performance over long distances and sometimes longer recovery times after training. What’s great about the SCL16A1 gene in horses is it spares muscles from fatigue by redirecting the lactate into the skeletal muscle cells, where it gets used as a sort of “respiratory fuel” to help ensure more effective metabolism over longer distances. Similar variations in genes of the SCL family are associated with better performance in endurance racing as well, he adds. Among the Arabians in Velie’s study, those that had inherited the SCL16A1 variant from at least one parent had more starts, higher earnings, greater earnings per start, and proportionally more wins than those that had not.
The scientists also noted a slightly less significant association between ACOX1 and ACTN3 and racing performance, said Velie.
ACOX1 slows the use of fatty acids to generate energy, making the process more efficient and providing energy over a longer period. Scientists had already suspected that this gene improved performance in Thoroughbred racehorses, and now it seems to be useful in Arabian racehorses as well, Velie said. Horses in his study that inherited a copy of the gene variant from one parent had higher earnings per start than those without it.
As for ACTN3, it codes for a protein that anchors filaments in the muscles, making sure they contract like they should during exercise. Horses that had inherited the gene variant from both parents performed best in longer-distance races.
Because they didn’t find enough cases of horses having these variants (one or both copies inherited from the parents), more studies are needed to understand the connection, he added.
Racing Arabians and Thoroughbreds: A Shared Gene?
The connection with Thoroughbreds, which also perform better with the ACOX1 gene, doesn’t necessarily mean these Arabian horses descended from Thoroughbred lines, Velie cautioned. It’s possible that the breeds both ended up with the same genes due to similar origins. “There is unquestionably a genetic link between Thoroughbreds and Arabians,” he said. “One need look no further than the geographic locations in which their foundation animals were sourced to see the shared history of the two breeds. However, the specific nature of their shared history has recently come under scrutiny.”
In the current study, none of the horses had any known Thoroughbred influence, said co-author Monika Stefaniuk-Szmukier, PhD, of the Department of Animal Reproduction, Anatomy and Genomics at the University of Agriculture in Krakow, Poland.
Finding Factors Affecting Performance
“The aim of the current study was not to identify ‘new’ genes associated with gallop racing performance, but instead to further investigate genes previously suggested as important for gallop racing,” Velie explained. “The results of the study did ultimately provide additional support and evidence for the involvement of three genes in relation to gallop racing performance. However, we are still investigating the specific nature of these associations (such as what biological pathways/mechanisms are affected by these genes and how this specifically alters racing ability/performance).”
Genetics are just one factor in performance, however, Velie added. Management and training are also important in getting a well-bred horse to the winner’s circle, he said.
Although the study focused specifically on Arabians racing in the gallop industry, many of these horses go on to have second careers as endurance racing horses, Velie said.