More selective breeding might help flat-faced dogs to breathe easier

Breeding programs could alter heritable dog characteristics to reduce the rates of brachycephalic obstructive airway syndrome (BOAS), a breathing disorder common in dogs such as Bulldogs, French Bulldogs and Pugs – according to a new study led by Dr. Joanna Jadwiga Ilska of the Royal Kennel Club, published May 13, 2026 in the open-access journal PLOS One.

Dog breeds with flat faces are frequently diagnosed with BOAS, which can cause noisy breathing, difficulty during exercise, an inability to cool off, and, in severe cases, even death. Flat-faced obese dogs have a higher risk of developing the disease, and tend to have more severe symptoms. But despite the high prevalence of this disorder in many popular dog breeds, the underlying genetic basis of BOAS has been poorly understood.

In the new study, researchers estimated the heritability of BOAS in the Bulldog, French Bulldog and Pug. They looked at respiratory health – determined by a standardized exercise test – and breeding records from the Royal Kennel Club from more than 4,000 dogs. Their analyses showed that two characteristics related to respiratory health were moderately heritable: 21-49% of variability in dogs’ respiratory function and 31-39% of variability in nostril size were attributable to genetics. Furthermore, poor respiratory function, narrow nostrils and high body weight tended to co-occur, suggesting it may be possible to improve respiratory health by avoiding breeding dogs with these traits.

French Bulldogs had the lowest prevalence of BOAS in the study, at 15.6% of tested dogs, compared to 18.9% of bulldogs and 19.8% of pugs. These rates are lower than previous estimates, possibly because few flat-faced dogs are screened for BOAS unless they show symptoms. The study also utilized samples that were 5–10 times larger than earlier reference values, and the authors note that potential health management improvements may have been made since previous studies.

For owners of the many existing dogs with BOAS, the Royal Kennel Club recommends management of symptoms by keeping dogs lean, giving them frequent breaks during walks and helping them stay cool in the summertime.

The new findings provide hope for future prevention of BOAS in flat-faced dogs, through the establishment of more selective breeding programs to help new generations to breathe easier. However, better breeding practices will depend on more widespread testing of dogs for respiratory health. Together, these efforts may help reduce the prevalence of BOAS population-wide and enhance the welfare of these popular breeds.

Dr. Joanna Ilska, geneticist and lead author of the paper, adds: “Our findings provide clear evidence that respiratory health in these breeds is influenced by genetic differences between dogs, and importantly, that improvement is achievable through selective breeding. By using objective tools like the Respiratory Function Grading Scheme, breeders can make more informed decisions that prioritize health, helping to reduce the prevalence of BOAS over time.”

“It is also important to recognize that this research is based on dogs within the Royal Kennel Club’s registered population and may not reflect those bred outside of this system. This highlights the value of Royal Kennel Club registration, as participation in schemes like the RFGS allows registered dogs to contribute to scientific research that supports the long-term health and welfare of the breed. 

“Increasing participation in health screening is also key to achieving progress and ensuring that future generations of these popular breeds can enjoy better quality of life.”  

In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/48zufqK

Citation: Ilska JJ, McDonnell F, Ladlow JF (2026) Quantitative genetic analysis of respiratory function and related traits in Bulldogs, French Bulldogs and Pugs. PLoS One 21(5): e0348023. https://doi.org/10.1371/journal.pone.0348023

Author countries: UK

Funding: The author(s) received no specific funding for this work.