Horse Speed Gene Identified; Commercial Testing Available

Irish researchers have found that horses with a specific mutation in the gene called myostatin (MSTN) have improved athletic performance.

"A variety of mammalian species with specific MSTN variants have characteristics of increased muscle mass," explained lead researcher Emmeline Hill, PhD, from the Animal Genomics Laboratory at University College Dublin, Ireland.

She said whippet racing dogs provide an example: Dogs that are heterozygous (have one copy) for a specific variant of the MSTN gene have significantly greater racing ability than dogs that are either homozygous (have two copies) for the mutation or dogs with no copies of the mutation.

Since this sequence in Thoroughbred racehorses had not yet been examined, Hill and colleagues analyzed DNA for variations in 148 Thoroughbred horses.

The researchers found that a single difference in the genetic code that changed a "cytosine" (C-allele) to a "thymine" (T-allele) base in the MSTN gene (which is over 6,000 base pairs in length) is strongly associated with best race distance in elite racehorses.

After validating the results in an addition 87 horses, the researchers suggested, "horses with the C-allele in both copies of the MSTN gene are suited to fast, short, races; horses with one copy of the C-allele and one copy of the T-allele compete favorably as middle-distance runners, and horses with two copies of the T-allele have greater stamina."

Hill and Irish Thoroughbred trainer Jim Bolger co-founded the company Equinome to provide a means for breeders, stallion managers, and bloodstock agents alike to test horses' MSTN gene sequences.

Test results will tell racehorse owners and trainers if a horse is ideally suited to racing over short, middle, or middle-to-long distances, the manufacturers say. Using this information, they could potentially optimize their purchasing and training decisions and enter their horses in the most suitable races. The test is also anticipated to help make more precise breeding decisions to maximize the genetic potential and value of their horses.

"While this information might be guessed by evaluating pedigrees and physical observations of individuals, using these traditional methods one cannot be certain of the actual genetic make-up of an individual," said Hill. "It is particularly important to realize that full-siblings with exactly the same pedigree page may be very different genetically. This test will provide that information, which cannot be determined with accuracy by any other means. Therefore the use of the test will provide an advantage in basing decision making in selection, racing, and breeding on accurate, scientifically ascertained information."

Ernie Bailey, PhD, geneticist and professor of veterinary science at the University of Kentucky's Gluck Equine Research Center, who is not associated with the company or test, noted, "This is the first application of genomics to performance in horses and is noteworthy. Up to now, molecular genetics has been used for parentage, coat color, and diseases in horses. This breaks new ground and goes directly to the interests of the horsemen.

"Racing performance is complex and undoubtedly there will be additional genes found that augment environment, management and opportunity," Bailey added.

Hill's data supporting the Equinome Speed Gene test was peer-reviewed and published in a scientific paper, "A sequence polymorphism in MSTN predicts sprinting ability and racing stamina in Thoroughbred horses," in the open access Public Library of Science journal, PLoS ONE.--Erin Ryder and Stacey Oke, DVM, MSc

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