PERFORMANCE AND PERSONALITY
While genetic tests for diseases, colors and parentage can provide DNA “proof” of a condition, those looking for genes associated with performance-related traits yield less definitive information. How or whether these genes are expressed can be influenced by training, environment and other factors.
For instance, performance testing, aimed primarily at Thoroughbreds, looks at multiple genes to attempt to predict a horse’s speed, stamina and overall potential for success at the racetrack. One factor these tests analyze is the myostatin gene, which controls the amount of muscle mass developed. Other components of the tests may predict a foal’s height at maturity as well as whether he will do better on dirt versus turf tracks.
Gait testing identifies a mutation on the DMRT3 gene that influences a horse’s ability to perform lateral gaits. The mutation is recessive—horses with two copies of the gene are common in Icelandic Horses, Paso Finos, Tennessee Walking Horses and other gaited breeds. The effects of carrying only one copy of the mutation varies by breed, but those horses generally perform the lateral gaits with less speed and facility.
Having a particular “performance” gene isn’t a guarantee, however. After all, many a racing phenom has had full siblings who washed out at the track, and every so often a horse with a modest pedigree takes the show world by storm. DNA is only part of the equation.
Another test, described by its manufacturer as “curiosity vs. vigilance,” analyzes a mutation that affects dopamine0 receptors in the horse’s brain. Horses with two copies of the recessive gene are defined as more curious—that is, more inclined to take an interest in and approach new objects. Horses with only one or no copies of the gene are more vigilant, or less inclined to explore their surroundings.
“An oversimplified example of this might be that horses who test positive for ‘curiosity’ might outperform those who do not in, say, a trail competition,” says Christa Lafayette, CEO of Etalon Inc. of Menlo Park, California, who adds that the real utility of the test will only be known once owners begin interpreting the results. “It’s going to be interesting to see what owners say about it and whether or not they find a correlation between curiosity/vigilance and certain types of activity.” sire and dam. If the sire is uncertain, then samples can be submitted from all possible sires.
By comparing inheritable traits in the DNA, these tests can confirm a foal’s parentage with efficacy greater than 99 percent; an incorrect sire can also be excluded with 100 percent certainty. “We compare the genetic profile of the sample of mane or tail hair submitted to our database profiles of the sire and dam,” Graves says. “We verify the parents and send those reports to the registries.” However, these tests do not reveal the breed of an individual horse.
Owners seeking to register their horses are the most common users of equine genetic testing. “The DNA test for parentage verification represents the largest number of samples tested,” Penedo says. “Most horse breed registries now require DNA testing for registration, which translates to hundreds of thousands of horses being tested yearly around the world.”
WHAT LIES AHEAD?
Like many other technologies, genetic testing is becoming faster, more affordable and thus more accessible. “The cost of sequencing a horse’s entire genome is coming down,” Graves says. “Today, this can be done for about $8,000 to $10,000. Soon, perhaps within 10 years, it will cost only about $1,000. At that point, the average horse owner will be able to sequence her horse’s entire genome.”
The challenge, says Graves, will be determining how best to use this information. “We still have a lot of work to do before we will know that,” she says. “We need to create maps of each breed of horse. This will enable us to look for desirable performance traits or for genetic anomalies in a horse
that has chronic health problems.”
Could genetically engineered “super horses” appear in the future? Possibly, with a new technology called “gene editing,” which Penedo describes as using “molecular scissors” to insert, remove or replace DNA sequences in the laboratory. “I can envisage that it will be tried in horses, but given the costs it is unlikely to become common practice,” she says. One application of this technology that she does foresee, however, “would be to correct the DNA sequence in an early embryo from highly valuable parents that is affected with a genetic defect, as determined from pre-implantation embryo genetic testing. The expectation is that the defective gene could be replaced by a normal gene, and the ‘edited’ embryo could then be implanted.”
In the meantime, the number of specific tests available---both for diseases as well as other aspects of a horse’s health and physiology---will likely continue to grow as researchers learn more about equine genetics. “It is a constantly evolving field,” de Kloet says. “Just as with human genetics, it’s going to change and evolve in the number of tests available and with regard to how the testing is being done. We have software programs and the computer ability to go through and look at a billion nucleotides in only a couple of days.”
To help with further research, Etalon Diagnostics offers several tests to the public, for conditions such as lordosis (“swayback”), that are in the “discovery stage”---that is, although there is some evidence of genetic factors for these conditions, the results of these specific
tests have not been fully validated by research studies. Etalon’s goal is to gain feedback from owners to help support the research.
“Our platform is collaborative, meaning that it relies in part on feedback from horse owners,” Lafayette says. “We look for associations between certain genetic mutations and performance or other health traits based on emerging research data. When we see a pattern that suggests a genetic link, we follow up with horse owners and track the input we receive from them. This leads to the discovery or confirmation of connections between genetic mutations and resulting traits faster than would be possible if we were to go the conventional research grant route.”
Lafayette admits, however, that this approach is still a work in progress: “Since this kind of horseowner-driven research platform has never been attempted before, the learning curve is steep,” she says. “We have to continually adjust our methods, studies, and the way we approach and present the information.”
The demand for genetic testing is already large and is likely to continue to grow in the coming years as the technology develops and new tests become available. Already, says Lafayette, labs like hers are receiving all kinds of requests from people who want more information about their horses: “Big ones, little ones, wild ones and pocket ponies, all colors, all disciplines. People want to know everything from color and health to speed and gait. Folks are excited to talk and learn more about their horses, as are we.”