The pugly truth: Scientists pinpoint the GENES that stop flat-faced dogs from being able to breathe - and call for a ban on breeding pups with these variations

Pugs and French Bulldogs might be some of the UK's most popular breeds, but scientists are now calling for a restriction on their breeding.

These flat–faced breeds are especially prone to a breathing disorder called brachycephalic obstructive airway syndrome or BOAS.

BOAS leaves dogs struggling to breathe, unable to exercise or cool off in the heat, and can be fatal in extreme cases.

Now, researchers have pinpointed the genes that may trigger this devastating condition.

Scientists from the Royal Kennel Club (RKC) assessed the respiratory health of over 4,000 dogs in their pedigree records.

This revealed that two characteristics related to breathing difficulties are moderately heritable, meaning they can be passed on from parent to puppy.

Scientists say that 21 to 49 per cent of the difference in a dog's respiratory health and 31 to 39 per cent of the variation in nostril size was down to genetics.

This suggests that BOAS rates could be significantly reduced by preventing the worst–affected dogs from breeding.

BOAS is a restriction of the upper airway tract caused by narrow nostrils, an elongated soft palate in a small head, and a windpipe that is proportionally too narrow.

Its primary cause is excessive breeding for 'aesthetically pleasing' characteristics, such as small heads, bulging eyes, short noses, and flat faces.

As such, the condition is almost exclusively found in flat–faced or 'brachycephalic' designer breeds.

The RKC looked at rates of BOAS in three of the most popular flat–faced breeds in the UK: Bulldogs, French Bulldogs, and Pugs.

Their data, collected through a standardised exercise test, showed that these flat–faced dogs had significantly higher rates of breathing difficulties than healthy breeds.

French Bulldogs had the lowest rates of BOAS among those breeds tested, with 15 per cent of all dogs in the RKC's records showing the debilitating condition.

Meanwhile, Bulldogs and Pugs had even higher rates of BOAS, with researchers finding the condition in 18.9 per cent and 19.8 per cent of dogs, respectively.

However, this only captures the dogs that are ranked as 'Grade 2', meaning they are 'clinically affected and have moderate respiratory signs of BOAS'.

Overall, 75 per cent of all dogs in the breeds tested are classified as having BOAS.

Likewise, this data only reflects dogs bred within the RKC's pedigree standards, which makes up just a small part of the population.

That means the true rates of respiratory issues among flat–faced breeds could be much higher.

Studies have shown that, despite the well–known health impacts, many owners find the wheezing and snorting caused by these issues to be cute or consider it normal for the breed.

This has meant that rates of BOAS have significantly increased over recent years as French Bulldogs and Pugs have become much more popular.

In the Netherlands, breeding of excessively flat–faced breeds was outright banned in 2020 on the grounds that it was cruel to force dogs to suffer for purely aesthetic reasons.

However, pinning down the genetic cause of respiratory issues might help breeders produce healthier animals without banning certain unhealthy breeds altogether.

Lead author Dr Joanna Ilska, a geneticist for the RKC, says: '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.'

As a result of their evidence, the Royal Kennel Club is updating its breeding advice for flat–faced breeds.

In the past, the RKC 'permitted' using dogs with Grade 2 BOAS for breeding, to avoid forcing inbreeding among the small number of healthy pedigree specimens.

But starting from May 13, all mating pairings involving a Grade 2 dog will be designated as 'red', meaning 'not recommended'.

In theory, this could allow breeders to continue producing flat–faced dogs while maintaining a lower risk of clinical respiratory issues.

A Kennel Club spokesperson told the Daily Mail: 'Our results showed that many flat-faced dogs in the three breeds we studied were free from clinical signs of BOAS, which is important because it demonstrates that respiratory health can vary considerably even within flat faced breeds.

'Breeders can gradually reduce the prevalence and severity of BOAS through informed breeding, without needing to remove entire breeds or rely on the development of genetic tests for the currently unidentified genes.'

However, the Kennel Club says that they cannot prevent the breeding of certain dogs.

While the results of respiratory tests are made available to breeders and potential buyers, the scheme is voluntary and is only designed to 'support responsible breeding decisions'.

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However, experts have questioned whether it will be possible to eliminate the harms of selective breeding without getting rid of these breeds' distinctive flattened faces.

Dr Rowena Packer, an expert on dog health from the Royal Veterinary College, told the Daily Mail: 'Extreme brachycephaly is associated with a much broader constellation of welfare problems beyond airway obstruction, including eye disease, overheating, sleep disruption, birthing difficulties, spinal abnormalities and impaired ability to express normal behaviours.

'Focusing too narrowly on selecting dogs with “better breathing” risks overlooking these wider harms.'

Dr Packer adds: 'The priority should therefore be breeding for overall health and functional conformation, rather than attempting to preserve extreme physical traits while selecting against one individual disorder.'