26 May 2026
Respiratory function heritability in key brachy breeds found to be comparable to other traits successfully selected for in companion animals.
Chris Simpson
Job Title
Image: Di Studio / Adobe Stock
Researchers have issued new calls for stakeholders to engage with dog breeders after a study demonstrated the potential to eliminate respiratory dysfunction through selective breeding.
The Royal Kennel Club (RKC) scholars investigated the heritability of respiratory function in three key brachycephalic breeds – the English bulldog, French bulldog and pug – in what was described as the most comprehensive genetic analysis of brachycephalic obstructive airway syndrome (BOAS) related traits in their UK RKC-registered populations to date.
They said the findings indicated lower prevalence estimates of BOAS in these breeds than previously reported and showed within-breed selection “has the potential to achieve meaningful genetic improvement”.
The authors analysed respiratory function grading scheme (RFGS) data from more than 4,000 dogs.
They found heritability estimates for RFGS grade ranged from 0.21 (English bulldog) to 0.45 (French bulldog), with the pug at 0.28, said to be a comparable level to many traits already successfully selected for in companion animals.
BOAS prevalence estimates ranged from 15.6% (French bulldog) to 19.8% (pug), with the English bulldog at 18.9%, in contrast to previous estimates that ranged from 51% to 64%.
Co-author Jane Ladlow, chief assessor and co-creator of the RFGS, said she was surprised by the finding, but with RFGS testing participation being voluntary, she suggested the true prevalence was likely higher.
Ms Ladlow said: “I think this is an optimistic look at the populations, but in one way it doesn’t matter, because if these are the dogs the breeders are testing, then these are the dogs the breeders are going to use.
“I don’t think it is this good, personally, [but] I think the breeders are learning quickly, and I think that’s positive.”
The paper suggested that, given the findings, the RKC should revise its RFGS breeding guidelines and that excluding grade 2 dogs – those exhibiting moderate respiratory signs of BOAS – from breeding “could accelerate genetic improvement in respiratory health”.
Asked if it will be possible to entirely breed BOAS out of these breeds, she said: “I think so.”
The RCVS and European specialist in small animal surgery added: “If we want better dogs, we have to engage with the breeders.
“The encouraging thing is that if you test for function, you can definitely improve the breed.
“[RFGS] is a cheap, easily accessible screening tool that breeders can use before they have any litters from their dogs, and they should be using it.
“If you use function, you almost certainly will get a more moderate anatomical appearance.”
She concluded: “We can test these dogs, we can identify the ones that should not be bred from, and we can show that it works.
“We originated the RFGS here in Cambridge, and I am proud to have contributed to this paper, to see it generating the kind of data that proves selective breeding works is exactly what the scheme was designed to do.”
The RSPCA’s head of companion animals science, Samantha Gaines, said the paper “must act as a wake up call”.
She added: “We urge the Royal Kennel Club to listen to their own research, not only implementing the changes it highlights are needed – but to go beyond this by committing to more moderate breed standards for these dogs, and prioritising health and welfare in their judging process.”