The results help quantify the negative health consequences associated with reproducing extreme body shapes.
Many people find their flattened faces cute, but among dogs raised with a squashed face, 11 percent or fewer of some breeds can breathe easily.
The results, published on February 18 in PLOS One, assess a major health cost breeding dogs with a shortened “brachycephalic” skull: chronically obstructed airways.
In the UK, some brachycephalic breeds “have become incredibly popular in recent years, notably the French bulldog,” says Francesca Tomlinson, a veterinarian and researcher at the University of Cambridge.
This popularity has helped shine a more direct light on the health problems these dogs can have, including brachycephalic obstructive airway syndrome (BOAS). The truncated skull of dogs may mean the airways are narrowedleading to labored, noisy, sniffling breathing. Researchers had previously studied the severity of the syndrome in pugs and bulldogs, but little was known about the condition in the many other flat-faced breeds.
Notes on breathing
The researchers used a scale of 0 to 3 to record the severity of brachycephalic obstructive airway syndrome (BOAS) symptoms in the dogs examined in the study. Pekingese (shown) had one of the lowest rates of grade 0, characterized by easy breathing.
From September 2021 to April 2024, Tomlinson and colleagues examined nearly 900 dogs from 14 additional brachycephalic breeds. The team performed standardized exercise tests on the dogs, classifying their breathing performance based on the presence of established syndrome symptoms like heavy or obstructed breathing. The dogs were rated on a 0 to 3 scale of symptom severity established in previous research, where 0 corresponds to no noisy breathing. The researchers also took detailed measurements of the dogs’ heads and bodies.
“The risk [of the condition] “Boxers and Staffordshire bull terriers, for example, have a fairly low incidence of respiratory problems. But the team found that Pekingese and Japanese-chinned dogs are in the high-risk category alongside bulldogs and pugs. Only 11 percent of Pekingese scored the healthiest rating of 0, compared to about seven percent of pugs.
The most important factors causing airway obstruction were the flatness of the face, the narrowness of the nostrils, and the relative obesity of the dog.
“[The study] confirms much of what science and biology has known for decades,” says Dan O’Neill, an animal epidemiologist at the Royal Veterinary College in London. “Artificial selection of dogs for abnormally short skulls reduces the ability of these dogs to breathe, sleep, exercise and live a full canine life.”
Findings like these may be useful as a starting point for more detailed studies into the physiological and genetic causes of this particular respiratory problem in different breeds. They could also be used in the future to manage short-faced breeds. Tomlinson says the respiratory score could be used in screening away from highly exaggerated features.
It is possible that the process has already started. The data on bulldogs and pugs used in this study comes from a study published in 2016. Since then, there has been much more attention to respiratory problems in short-nosed breeds, Tomlinson says.
“I hope this means that [breeders] selected dogs that are less severely affected and could have helped move the breeds to a healthier location.
