The work being done to monitor and detect gene doping practices and understanding the future perspectives in breeding
The pursuit of genetic perfection no longer ends with traditional selection. Alongside meticulously planned breeding programs and increasingly sophisticated genomic profiling, a new and controversial possibility is quietly gaining ground - gene doping. The idea of altering a thoroughbred’s gene expression to enhance muscle power, endurance, or cellular recovery is both compelling and profoundly unsettling.
In experimental research, these tools are already being tested using animal models and although no official cases have been reported in racing so far, the specter of their potential use is growing increasingly real. The discourse around gene doping and gene therapy more broadly, is emerging with greater urgency, raising complex ethical, technical, and regulatory questions.
This is an extremely dangerous development, not only because it threatens the integrity of competition, but also due to the unknown risks it poses to the animals themselves, who may be subjected to genetic manipulation without the capacity to understand or consent. Both the World Anti-Doping Agency (WADA) and the International Federation of Horseracing Authorities (IFHA) have taken a clear stance against such practices, prohibiting their use in both human and equine athletes.
Despite these regulatory safeguards, the rapid pace of genetic science is testing the limits of current frameworks. Advances in biotechnology are no longer confined to the laboratory or speculative discourse they are beginning to manifest in the real world. While equestrian regulators have outlined strict prohibitions, enforcement is inherently reactive, often lagging behind innovation. The gap between what is technically possible and what is legally permitted is widening, and within that space, experimental applications of gene editing are quietly advancing. It is in this grey zone, between regulation and research, that the first real-world example of genetically edited equine athletes has emerged.
This shift from theory to application became strikingly evident in October–November 2024, when Argentina’s biotech firm Kheiron Biotech announced the birth of five genetically edited polo foals, marking the world's first CRISPR‑Cas9–engineered equine athletes.
These horses were derived from mesenchymal stem cells of Polo Pureza, a champion Argentine polo mare celebrated in the breeders’ Hall of Fame. Rather than cloning, scientists used CRISPR‑Cas9, a highly precise genome-editing tool, acting like molecular scissors to modify specific DNA segments. The primary target was the myostatin (MSTN) gene, which restricts muscle growth by silencing or altering this gene. The resulting foals were designed to possess enhanced muscle mass and explosive speed, while preserving the mare’s natural agility and temperament.
The editing process involved removing an oocyte’s nucleus, replacing it with DNA from Polo Pureza’s edited stem cells, and implanting the embryos into surrogate mares; five live foals were born from eight pregnancies.
In the context of the horse racing industry, where the value of a Thoroughbred can hinge on milliseconds of performance and the ability to sustain speed over distance, gene editing presents an especially tempting field.
Can we imagine this scenario extending into the racing world?
Scientifically, the answer is yes. The same techniques used to enhance athletic potential in polo ponies could, in principle, be applied to racehorses. Several genetic traits directly influence race performance and could be enhanced through precise gene editing. The range of traits that could be enhanced is both broad and strategically targeted. The ultimate goal would be to produce a horse that runs faster, resists fatigue better, recovers more quickly, and possibly even suffers fewer injuries, all thanks to targeted genetic interventions.
One of the primary areas where gene editing could intervene is muscle development. Racehorses rely on explosive power and speed, and one of the key genes responsible for regulating muscle growth is myostatin (MSTN).
This gene acts like a natural limiter, preventing muscles from growing excessively. By suppressing or modifying MSTN, it’s possible to significantly increase the mass and strength of skeletal muscles, giving horses more power during acceleration and allowing them to maintain higher speeds.
Enhancing muscle development could be especially valuable for short-distance (sprint) races, where raw power is a major performance factor. Alongside MSTN, scientists may also target follistatin, a glycoprotein that naturally inhibits myostatin and encourages muscle growth. Its manipulation, already studied in other species, could serve as an indirect yet powerful enhancer of muscle development in horses.
Another key aspect involves muscle endurance and recovery, where hormones like Insulin-like Growth Factor-1 (IGF-1) and growth hormone (GH) play essential roles. IGF-1 stimulates protein synthesis and helps in repairing tissue damage after intense effort.
Gene therapy involving IGF-1 has shown increased muscle mass in animal studies, even without training. When combined with exercise, its effects are amplified, and it may also reduce muscle loss during periods of rest (highly relevant in racing horses recovering from injury or off-season periods).
Performance in longer races, however, is not just about power, it’s about how efficiently a horse uses oxygen. Here, oxygen transport genes like erythropoietin (EPO) and HIF-1 become highly relevant. By increasing red blood cell production, these genes allow muscles to receive more oxygen during effort, delaying fatigue and improving aerobic endurance. In practice, a horse with genetically enhanced EPO expression could maintain high levels of exertion for longer without performance dropping off. In addition, HIF-1 also activates other processes, such as the formation of new blood vessels (angiogenesis) and improved mitochondrial function, both of which contribute to athletic stamina.
There is also the possibility of influencing muscle contraction efficiency through genes like ACTN3, which is associated with fast-twitch muscle fibers, those responsible for rapid, explosive movements. Variations in this gene may help differentiate a horse better suited to sprints versus long-distance racing.
Beyond functional performance, gene editing also opens the door to phenotype modification, adjusting physical traits that contribute indirectly to racing ability. This includes aspects like limb length, back structure, stride angle, body mass distribution, and joint strength. Studies have identified quantitative trait loci (QTLs) and genes like TBX15 that influence skeletal development and muscle fiber differentiation.
By acting on these, one could refine the physical ideal standard of a horse to better match the ideal conformation for speed and biomechanics. This would mark a radical shift from traditional breeding, where physical traits emerge through generations of selection, to a scenario where conformation is engineered at the embryonic stage.
In essence, the application of gene editing in horse racing presents the theoretical possibility of designing equine athletes tailored not only for general fitness, but for specific racing distances, styles, and even track conditions. A genetically customised thoroughbred could, in theory, be built for explosive sprints, long-distance endurance, or optimal biomechanics on certain surfaces.
“Does the end justify the means?”
This timeless question, posed by Machiavelli centuries ago, feels strikingly relevant in today’s ethical debate over gene editing in sport horses. The growing scientific evidence that gene editing in horses is not only possible but increasingly feasible brings to the forefront a complex and deeply important moral dilemma. Just because we can manipulate the genome of a future equine athlete, should we?
At the heart of the discussion lies the fundamental value of fair play, a core principle that defines the legitimacy of competitive sport. If one horse is genetically enhanced before birth while others are bred through traditional means, can they still compete on equal terms? Gene editing, by its very nature, introduces an artificial advantage, one that is not earned through training, nutrition, or breeding judgment, but through direct technological intervention at the biological level.
Such practices risk turning the racecourse into a competition not of horses, but of laboratories and geneticists. The fairness of the sport would be compromised, not only for competitors but for owners, breeders, and spectators who trust in the authenticity of the contest. Moreover, equine athletes cannot give consent to be genetically modified. Altering their genome for human-defined goals raises profound questions about animal welfare, autonomy, and dignity. Is it ethical to “design” an animal for performance, knowing that such manipulation may also carry unknown health risks or reduce genetic diversity?
While innovation has always shaped sport, from training techniques to equipment, the line between enhancement and manipulation must be clearly drawn. Gene editing, when used for performance purposes, crosses that line. It challenges the spirit of horsemanship, the unpredictability of natural talent, and the integrity of racing itself. Ultimately, preserving fair play may mean accepting the biological limits of even the most elite Thoroughbreds and recognising that what makes sport meaningful is not control over the outcome, but the uncertainty of it.
Indeed, these ethical concerns have not gone unnoticed by the governing bodies of equine sport. Organisations such as the World Anti-Doping Agency (WADA), the International Federation of Horseracing Authorities (IFHA), and most notably the British Horseracing Authority (BHA) have already taken a firm and proactive stance against the use of gene editing for performance enhancement.
The BHA, in particular, is now leading the way globally in developing and implementing anti-gene doping protocols within its world-class equine anti-doping programme. In a decisive move to protect the integrity of British racing and the welfare of thoroughbred horses, the BHA has officially expanded its anti-doping operations to include routine testing for gene doping, both on raceday and out-of-competition.
This includes the detection of direct DNA manipulation via gene editing as well as gene transfer, where foreign genetic material is introduced into the horse’s cells to boost athletic traits or accelerate recovery.
Such practices are clearly prohibited under the Rules of Racing, and the BHA recognises gene doping as a serious and growing threat, not only to fair competition, but also to equine health and the future integrity of the breed.
To confront this emerging risk, the BHA has invested nearly £2 million in cutting-edge scientific research in collaboration with the LGC laboratory in Fordham, establishing a dedicated gene doping detection team as early as 2019.
In partnership with the Centre for Racehorse Studies, researchers at LGC have successfully developed analytical techniques capable of identifying evidence of gene doping, achieving UK Accreditation Service approval to perform this next generation of highly sensitive testing. This new gene doping detection framework is already active, forming part of a comprehensive testing programme that combines random sampling with intelligence-led investigations.
The goal is not only to ensure compliance with the Rules of Racing, but also to act as a powerful deterrent preserving the fairness of the sport and prioritising the welfare of the horse. With this initiative, the BHA is sending a clear message: that the use of genetic engineering to manipulate equine performance will not be tolerated, and that the tools now exist to detect and act upon it.
Gene-doping represents the current frontier of innovation and concern within the world of racing. While science continues to demonstrate the increasing feasibility of genetic intervention, both in theory and in practice, this progress brings with it a set of unresolved questions that extend beyond biology or regulation.
The potential to influence a horse’s genetic makeup with surgical precision is no longer a distant possibility, but a reality under active discussion. Yet, embracing such power uncritically could signal a shift in the very foundation of equestrian sport: from a celebration of natural ability, training, and partnership, to a controlled outcome engineered in a lab.
At its core, this conversation is not just about doping, it is about the boundaries between humans and nature, between technological capability and ethical restraint, and between competition and manipulation. The choices made now will shape not only the future of the sport, but also its meaning. As the line between what is possible and what is permissible becomes increasingly thin, the challenge will not only be to detect gene doping, but to decide, collectively, whether sport should allow itself to go down this path at all.
The principles of genetic research and its impact on the Thoroughbred racing world
Words - Holly Robilliard and Cassie Fraser
GMO thoroughbreds? Superhorses created in the lab? Is genetic doping a real “thing”? It’s time for a reality check and a good, hard look at what’s real, or even possible, and how it can hurt or help the thoroughbred industry.
Breeders, trainers, and owners continually seek a competitive edge, striving to produce horses with the speed, stamina, and resilience needed to succeed on the racetrack. Concurrently, there is increasing pressure and responsibility to minimise animal discomfort, injury, and death in a public forum. Therefore we must carefully examine and balance all the tools at our disposal before determining which ones to use and how.
Interestingly, there is a growing technology that may be of more notable controversy than even horse racing: The power of genetics. Perhaps the greatest power man has ever wielded, genetics has sparked numerous debates over the good and evil it can bring. As with most new things, there is a significant fear of the unknown, so how do we even begin to understand it? In short: research, homework, and fact-finding. Let’s look at what is fact, scientifically known, and possible today, and then consider what may be possible in the future.
Genetic Influences on Equine Performance
DNA, often called the “blueprint of life,” holds the key to a horse’s inheritance and development, from its physical prowess, size and speed, to temperament and abilities. By studying their genetics, we can unravel the intricate code that dictates the pre-existing traits and characteristics of these powerful athletes. This information can then be utilised in our breeding and performance programs to improve suitability and success, all while upholding ethical standards and preserving the integrity of the sport.
The general rule for Mendelian traits is that a foal inherits one allele from each parent for a given gene. If the inherited alleles are the same, the horse is called homozygous for that gene. If they are different, they are heterozygous. As heterozygosity goes up, genetic diversity is increased, resulting in more variation in the genetic content. This results in a greater adaptability to environmental stressors and change, leading to a more robust animal and population. With equine genetics, we tend to focus on three kinds of genes: Causatives - genes/variants that directly cause a trait or condition, Correlatives - genes/variants that appear alongside, or in common, with a trait or condition, and Risks - genes/variants that increase their likelihood/risk of acquiring that trait or condition.
A thoroughbred study by Momozawa et al. found an association between the dopamine d4 receptor (DRD4) gene and a measure of temperament. In the study, “curiosity”, defined as, “an interest in novel objects and a willingness to approach them”, was prevalent in horses with a particular gene variant. Horses preferring to observe carefully, from a distance, were of the opposite variant type, named “vigilance”. Although further research is required, it is not unreasonable to consider that temperament affects a horse's ability to learn, break from the gate, or handle the pressure of large crowds on race day.
Another performance trait, perhaps of more notable interest to thoroughbred enthusiasts is the “speed” gene, myostatin (MSTN). This insertion results in increased muscle growth in horses and other mammals. Genetically, horses can have two copies of the “Sprint” variant, two copies of the “Endurance” variant, or one copy of each, “Sprint/Endurance.” Thoroughbreds homozygous for the Sprint variant tend to excel earlier in age, at shorter distances (8 furlongs or less) with quick bursts of speed. Horses homozygous for Endurance excel later, and at longer distances (9 furlongs or more). However, heterozygous horses won at all distances, having both quick bursts of speed and endurance capabilities.
Using genome-wide association studies (GWAS), scientists can analyse equine DNA and identify specific genes associated with various health and performance traits. This research holds immense promise, pinpointing genes responsible for desirable traits like speed, temperament, gait, size, and overall health. So how can we use it to produce horses with optimised genetic profiles for racing, while minimising risk and injury? The answer lies within our breeding programs.
Breeding & Buying Optimised With Genetics
For generations, breeders have been making selections for observed traits, such as pedigree, racing history, prior offspring performance, and conformation. Additionally, “Nicking,” the strategic crossing of certain lines with an observed affinity for one another, is another well-known method used to make breeding decisions. These techniques may be successful, as the chosen bloodlines possess underlying genetic traits that express and complement one another. Given science today, the next evolutionary step in this process is to genetically test and confirm the desired traits are present and will be passed on in the most advantageous combinations.
Inbreeding (having drastically reduced genetic diversity) poses a significant challenge within the thoroughbred racing industry due to the closed nature of the studbook. Science shows that a 10% increase in inbreeding reduces a horse’s likelihood of successful racing by 7%. Essentially, higher genomic inbreeding correlates with poorer performance. Traditionally, we have relied on pedigree and conformation to make mating decisions. Today, using actual genetics, we can calculate accurate genomic inbreeding and work toward decreasing it. On paper, two mares (full siblings) would appear to have the same inbreeding value. In reality, they can differ greatly, and if bred to the same stallion, may produce foals with drastically higher, or lower, genomic inbreeding values.
Using myostatin again, let’s look at a stallion that, by conformation and pedigree, appears to be the perfect match for your mare. Genetically, the mare is Sprint/Endurance and the stallion is Sprint/Sprint. This would result in a foal who is 50% likely to be Sprint/Endurance and 50% likely to be Sprint/Sprint. Now, if you breed that same mare with a stallion who has, at a minimum, one copy of endurance, the foal would still have a 25% chance of being Sprint/Sprint. However, it would also have a 50% chance of being Sprint/Endurance, and a 25% likelihood of being Endurance/Endurance, giving it longer-distance capabilities.
Beyond discovering performance-related traits, genetic research plays a vital role in promoting the overall health and sustainability of the breed. Health and soundness risks, such as Recurrent Laryngeal Neuropathy (RLN), or “roaring”, Kissing Spines, and Tendinopathy are being actively developed as genetically testable variants. Some of these traits can limit a thoroughbred's pre- or post-racing career. Other predispositions, like Chronic Idiopathic Anhidrosis (CIA), or “non-sweater,” or Fracture Risk, can be life-ending if they go undetected.
Through the use of genetic testing and associated technologies, breeders can “Build-A-Horse” to their specifications by crossing specific sires and dams using confirmed, heritable genetics, that create that optimal foal. By making breeding decisions based on maths and science, we can reduce the presence of undesirable health traits in our programs.
As more thoroughbred owners utilise genetics, collaborating researchers will continue identifying areas of strength and vulnerability in health and performance. This knowledge empowers breeders and buyers to make informed decisions that preserve genetic diversity and ensure the long-term strength of thoroughbred bloodlines. Given the considerable investment of both resources and effort involved in the production and training of horses destined for the track, decreasing risk and increasing financial management is paramount. Remarkably, the cost of utilising genetic testing to ascertain a horse’s optimal race distance is less than one week's feed, and can ultimately save owners and breeders both time and money.
Navigating Ethical Considerations
As genetic research becomes increasingly integrated into the thoroughbred racing industry, it’s wise to approach this technology with foresight instead of fear. Whilst it offers unprecedented opportunities for improvement and advancement, this research also carries the potential for unintended consequences and ethical dilemmas that must be carefully navigated.
The topic of cloning has been hotly debated in the last decade. The first reaction appears to be to “ban” it in certain registries and competitions. Interestingly, the fears stoked by this technology have not materialised into truth for a seemingly simple reason: You can replicate the genetic code of an animal, but it’s another thing entirely to replicate the uterine environment, the training, feeding, life experiences, and competition circumstances.
Another recent concern within the industry is the concept of “gene doping” to create superhorses, which involves artificially modifying an athlete's genes to enhance their performance. For example, the myostatin gene may become the target of genome editing in horses, as it alters the amount and composition of muscle fibre types. Although there are no known foals born, to date, with genetically altered myostatin, could it happen? Maybe. Would the effect be instant in something like myostatin? No. Why? Because that’s not how it works! A live animal has a fully formed physical plan in place, especially for things such as muscle, tendons, and bone. Today’s most advanced gene therapies tend to be extremely targeted regions, take months to years to work, and are extraordinarily expensive.
Assuming it’s possible to change the myostatin disposition of a horse, could we detect that it was manipulated? The answer, according to multiple experts, is a very strong, “maybe”. Technique and timing would matter as would the simple question of, “Could this foal’s parents have passed on this genotype?” As technology advances and provides the opportunity for a competitive edge, it’s safe to say that someone will try it. What then? The answer may just come down to numbers, like everything else on the track.
So, with all of this knowledge, can someone choose a bunch of genetic traits and create a Superhorse? Although you hear about it every day, complex genetic editing is just in its infancy. It is possible to change a gene or variant within an embryo- We’ve been doing it for decades already. So why not a Superhorse? Well…consider the following:
It’s not easy to insert a single correct genetic edit that results in a living animal.
It takes a large number of iterations and time for that one change.
The process can be super expensive. Multiply this by many dollars and much more time for every additional genetic change you wish to add.
Once you’ve produced genetic change, now you have to wait years to see the foal perform at which point your choice of changes may no longer be the winning combination!
Although we are likely years away from this being a feasible, let alone common, issue, we need to take steps now to understand genetics and devise a reasonable path forward. Preventing the misuse of gene editing could be as simple as creating a standardised genetic testing requirement via hair sample in addition to the standard parentage verification. This initial hair sample would serve as a genetic baseline, offering a comparison for those taken at a later date when genetic modifications are suspected.
By adhering to rigorous standards of ethical conduct, transparency, and accountability, we can harness the full potential of genetic research while safeguarding the welfare and integrity of thoroughbred racing.
Conclusion
Genetic research and testing represent a game-changing advancement for the thoroughbred racing industry. It is a powerful tool for enhancing the quality, health, and performance of racehorses- all of which are required to maintain the sport's integrity. As we increase our understanding of equine genetics and discover new traits applicable to the thoroughbred, we can produce healthier, more competitive horses, while reducing the historical struggles of inbreeding and breakdown. Although we must be careful to adhere to the ethical code set forth within the industry, by utilising genetics to build the next generation of improved thoroughbreds, we can take ownership of the technology and usher in a new era of excellence and innovation within the sport.
Sources
Hill, E. W., Stoffel, M. A., McGivney, B. A., MacHugh, D. E., & Pemberton, J. M. (2022). Inbreeding depression and the probability of racing in the thoroughbred horse. Proceedings of the Royal Society B, 289(1977). https://doi.org/10.1098/rspb.2022.0487.
Momozawa, Y., Takeuchi, Y., Kusunose, R., Kikusui, T., & Mori, Y. (2005). Association between equine temperament and polymorphisms in dopamine D4 receptor gene. Mammalian genome, 16, 538-544. https://doi.org/10.1007/s00335-005-0021-3
Rooney, M. F., Hill, E. W., Kelly, V. P., & Porter, R. K. (2018). The “speed gene” effect of myostatin arises in thoroughbred horses due to a promoter proximal SINE insertion. PLoS One, 13(10). https://doi.org/10.1371/journal.pone.0205664
Tozaki, T., Ohnuma, A., Nakamura, K., Hano, K., Takasu, M., Takahashi, Y., ... & Nagata, S. I. (2022). Detection of indiscriminate genetic manipulation in thoroughbred racehorses by targeted resequencing for gene-doping control. Genes, 13(9), 1589. https://doi.org/10.3390/genes13091589