Exploring the “Speed Gene” in Racing Arabians

With the recent explosion in research over the past decade, genes that contribute to health, disease, training, and performance are being uncovered quickly. Genes professed to dictate speed, agility, ideal racing distance, trainability, ease with which a horse can transition between gaits, and many others have all been described. One of the latest to join the parade is the ACTN3 gene, touted by some as a true “speed gene.”

“ACTN3 codes for a protein in skeletal muscle that plays a key role in muscle contraction. That protein, called α-actinin-3, reportedly affects energy production in the muscle, which can dictate fast- versus slow-twitch muscle fiber function. In essence, this means that the ACTN3 gene could help horsemen devise training regimes appropriate for either endurance or sprinting,” explained Laura Petroski-Rose, B.V.M.S, a Kentucky Equine Research veterinarian.

To explore the role of ACTN3 in racing Arabians, DNA was collected from the gluteus medius muscle of 15 purebred Arabian horses. The expression of the gene and sequence of the gene, were analyzed in each horse before and after training.

The researchers found:

• A significant decrease in ACTN3 expression in the skeletal muscle of Arabian horses while training for flat racing. Specifically, as training increased, the amount of ACTN3 expressed decreased;
• Confirming those findings, the highest amount of mRNA—which acts as a liaison between the gene and protein—was detected in the muscle of untrained horses. The lowest expression was identified at the end of the racing season when horses had fully adapted to the physical effort of training;
• Analysis of the ACTN3 gene sequence identified 14 differences, called polymorphisms; and
• Two of those polymorphisms were proposed as the causative mutations that might affect gene expression.

Based on those findings, the researchers concluded, “The presented gene expression analyses indicated the significant role of the ACTN3 gene in adaptation to physiological effort in horses. Due to previous reports and our findings, further studies should be conducted to verify the usage of the ACTN3 gene as a potential genetic marker for determining exercise performance in Arabian horses and other horse breeds.”

“Genetic analysis is definitely nosing its way into the equine industry, helping owners and trainers during the prepurchase, training, and competition phases of their careers. Another aspect to consider while training young horses is bone health,” Petroski-Rose noted.

She added, “Kentucky Equine Research recommends supporting bone health in these animals with Triacton—a triple-action supplement designed to improve bone density and support digestive health in horses. This product contains an array of highly bioavailable minerals and vitamins essential for sound skeletal development and maintenance, including magnesium, boron, silicone, iodine, zinc, manganese, as well as vitamins A, C, D, and K.”

*Ropka-Molik, K., M. Stefaniuk-Szmukier, A.D. Musiał, et al. 2018. Sequence analysis and expression profiling of the equine ACTN3 gene during exercise in Arabian horses. Gene. 685:149-155.