- Horses
- Health
- Diagnostics
11. 10. 2026
Polygenic Score in Horses: Lessons from Racehorse Fractures
Can a polygenic score alter a horse's genetic makeup? Short answer: no. A polygenic score doesn't change a horse's DNA. It adds up the tiny effects of hundreds to thousands of genetic variants into a single number that estimates predisposition – a risk, not a diagnosis. Nowadays, scientists know that some of the complex conditions in horses are due to the combined effect of a number of variants rather than the result of a single faulty gene mutation, and one of the most interesting examples currently available is that of Thoroughbred racehorses.
A variety of non-genetic factors affect the likelihood of fractures in racehorses, such as the intensity of their training, their diet, the way they are managed, the condition of the track, and the racing schedule. Yet genetics seems to be involved as well. Studies that have looked at the genome of Thoroughbreds have found multiple areas connected to a higher risk of fracture. This suggests the risk comes mostly from many small effects, with a few stronger signals. More recent studies have gone further by using methods to explore the biological pathways involved in bone remodeling. However, this does not mean we can currently predict if a specific horse will get injured. Instead, it suggests that in the future it might be possible to identify horses that are more likely to have bone problems and adjust their care accordingly.
Whole-genome sequencing makes it possible to detect subtler and rarer effects. This technique provides scientists with almost the full picture of the genetic variability of a particular horse. But whole-genome sequencing by itself isn't very useful. The simpler task is to read the genome, truly understanding it is a completely different matter. The data becomes useful only when it is connected with actual records such as the animal's medical history, performance data, training logs, and information about the environment.
If detailed and complete data sets become available, there could be a lot of potential for their use. For example, they could help predict an animal's chance of developing problems, how it responds to training, how it recovers after exercise, its risk of metabolic disorders, its chance of getting sick, and even some of its behavior patterns. For now, most of these ideas are still more theoretical than practical. The future of equine genetics probably will not rely on finding one "performance gene" or one "behavioral gene." Instead, it will come from understanding how hundreds to thousands of genetic signals work together to shape a full and complex animal.
