Are we any closer to linking DNA to ability?
For as long as horses have been bred for sport, breeders and riders have sought to answer the same question: what makes one horse a champion and another simply average? Conformation, training, nutrition, and management all play their roles, but could part of the answer be written in the horse’s DNA? Advances in equine genomics over the past two decades have begun to shed light on this question. Yet the relationship between genetics and performance remains far from straightforward.
The rise of equine genomics
The sequencing of the horse genome in 2007 marked a turning point in equine science. Researchers could now explore the genetic blueprint underlying traits like speed, stamina, muscle development, and even behaviour. This opened the door to studies comparing elite equine athletes with their less accomplished peers, in the hope of identifying genetic ‘markers’ that could predict future performance.
One of the earliest and most publicised findings was the ‘speed gene’, a mutation in the myostatin (MSTN) gene. In Thoroughbreds, MSTN variants were associated with racing distance aptitude: one form favoured sprinting, another middle distances, and a third long endurance races. This discovery excited breeders and investors, suggesting a genetic test might help select foals destined for particular racing careers.
However, MSTN is an outlier in terms of clarity. Most traits in sport horses, like jumping scope, dressage movement, carefulness, temperament, are polygenic, influenced by hundreds (if not thousands) of genes interacting with environment, training, and chance.
Jumping, dressage, and beyond: What do we know?
In recent years, studies have looked at showjumping and dressage populations in Europe, seeking genomic regions linked to traits like the bascule, canter quality, and scope.
- Showjumping ability: Research has identified some genomic regions potentially associated with power and technique. However, no single ‘jumping gene’ has emerged; instead, performance appears to be the cumulative effect of many small genetic contributions.
- Dressage aptitude: Studies have explored the genetics of gaits, particularly trot symmetry and elasticity. Again, the results show a polygenic influence, with heritability estimates suggesting that genetics plays a role but does not predetermine talent.
- Temperament and behaviour: Some genes linked to dopamine and serotonin pathways may influence reactivity and trainability. These findings are intriguing, but environment, handling, and rider influence remain powerful shapers of behaviour.
Overall, while researchers can identify regions of the genome with potential influence, no marker is strong enough to be predictive on its own
The limits of prediction
Why is predicting performance from DNA so difficult?
- Polygenic traits: Unlike coat colour or height, performance is not dictated by one or two genes. It involves the interplay of many, each contributing a tiny fraction.
- Epigenetics: How genes are expressed can be influenced by the environment. Training, nutrition, stress, and injury all affect gene expression, i.e. how, and to what extent, a gene is ‘expressed’ by the horse.
- Management and training: A horse with excellent genetic potential may never reach it under poor management, while a well-produced horse of modest genetic background may achieve far more than expected.
- Sample sizes: Many equine genomic studies are limited by smaller populations compared to human or cattle research. This makes it more challenging to draw statistically robust conclusions.
The role of genetic testing today
At present, most equine genetic testing offered commercially is limited to:
- Parentage verification (confirming lineage).
- Disease testing (identifying carriers of genetic disorders like PSSM1, SCID, HYPP).
- Coat colour and simple traits.
Definitions
PSSM1 – Polysaccharide Storage Myopathy (Type 1)
This is a muscle disorder caused by abnormal storage of glycogen. Horses with PSSM1 may show signs such as tying up, muscle stiffness, reluctance to move, or poor performance. The condition is managed with diet and exercise, but breeding carriers is discouraged.
SCID – Severe Combined Immunodeficiency
This is an inherited condition seen mainly in Arabians. Affected foals are born without a functioning immune system, making them unable to fight infections. Sadly, affected foals rarely survive past a few months. Carrier testing has helped reduce the prevalence of this condition.
HYPP – Hyperkalemic Periodic Paralysis
This is a genetic muscle disorder linked to a mutation in the Quarter Horse sire Impressive. Affected horses can have episodes of muscle tremors, weakness, collapse, or even sudden death due to high blood potassium. Responsible breeding (avoiding affected stallions/mares) has greatly reduced cases.
WFFS – Warmblood Fragile Foal Syndrome
This is a connective tissue disorder caused by a collagen gene mutation, most common in Warmblood populations. Foals born with two copies of the gene have extremely fragile skin and connective tissue and are typically non-viable. Carriers appear normal, but two carriers should never be bred together.
Performance-related tests (e.g., ‘jumping aptitude’ panels) are marketed, but many scientists urge caution. Without large-scale validation, their predictive value is limited and may risk misleading breeders.
That said, genomic information is increasingly used in breeding value estimation in some studbooks. Just as dairy cattle breeding has successfully integrated genomics to improve milk yield, equine studbooks are beginning to combine pedigree, performance data, and DNA information into more accurate predictions of breeding value. The Warmblood Fragile Foal Syndrome (WFFS) carrier test is an example of a tool that is already reshaping breeding strategies by helping to avoid risky pairings.
The future: Genomics as one piece of the puzzle
So, are we any closer to linking DNA to ability? The answer is: a little, but not enough to predict the next superstar with a cheek swab.
Where genomics is likely to shine in the near future is in population-level breeding programmes. By combining large datasets of performance records with genetic information, studbooks may refine their selection tools, gradually increasing the proportion of foals with higher potential. At the level of the individual horse, however, training, health, environment, and rider skill will continue to play a decisive role.
Conclusion
DNA undeniably influences equine performance, but it is not destiny. Genetics provides the framework, while environment and management determine how far that framework can be developed. Breeders and riders alike should view genetic science as a powerful tool, one that complements, but does not replace, horsemanship, careful selection, and skilled training.
The dream of predicting the next Valegro or Explosion W from a genetic profile alone remains distant. For now, the best we can do is continue to combine science with the art of breeding, trusting the blueprint, the bloodlines and the human eye.