Fri, 03/24/2023 - 4:34am

Breathing Easier

New screening test for brachycephalic breeds helps identify airway obstruction

Photos courtesy of Purina


The trending appeal of the French Bulldog as the quintessential companion boosted the breed’s American Kennel Club registrations to the top spot in 2022. After two years ranked as the number-two breed, the Frenchie ended the 31-year run of the Labrador Retriever as the most popular breed in the country.

Serendipitously, a dog of the most popular breed was also the number-one all-breed show dog in the country in 2022. The now 4-year-old fawn male Frenchie who achieved the top ranking is named “Winston” (MBIS/MBISS GCHP Fox Canyon’s I Won The War At Goldshield CGCA CGCU TKN). He is the winningest French Bulldog in breed history, with more than 80 Bests in Show, and was awarded Reserve Best in Show at Westminster last year.

Winston’s extraordinary type, conformation and personality are readily apparent. But he also has exceptionally good health, something not to be taken for granted with brachycephalic breeds, particularly French Bulldogs, Bulldogs and Pugs, which may have extreme physical characteristics that impair their breathing.

These short-nosed breeds charm mainstream dog lovers, as well as dedicated breeders and exhibitors, with their cuteness and huge personalities. Yet for some dogs, a casual stroll may cause noisy breathing or heavy panting, indicators of brachycephalic obstructive airway syndrome, or BOAS.

An upper-airway breathing disorder, BOAS is a progressive, inherited condition that can shorten a dog’s lifespan. Affected dogs often cannot run without labored breathing, eat without gasping for breath or sleep without obstructing. Arguably, these dogs are neither healthy nor happy.

A new screening tool, called respiratory function grading (RFG), promises to be a game changer in helping to reduce the incidence of BOAS disease. The RFG provides an objective measure of a dog’s respiratory function, enabling breeders to select dogs less likely to produce puppies at risk for BOAS, especially when combined with selecting against dogs with exaggerated anatomical features.

Dr. Kelley Thieman of Texas A&M University listening to the breathing of a Pug for respiratory function grading.


“We can improve the life of the individual dog with BOAS with surgery, but this is not the solution,” says Jane Ladlow, VetMB, DECVS, of Cambridge University in the U.K., who led the RFG research. “The answer lies with health-focused breeding. Less extreme is better when it comes to exaggerated conformation in dogs.”

Developed by The Kennel Club and the Cambridge University BOAS Research Group, RFG testing was introduced in the U.S. last January at the Rose City Classic Cluster in Portland, Oregon, by the Orthopedic Foundation for Animals (OFA), which licensed its use for U.S. and Canadian dogs. The parent clubs for the Bulldog, French Bulldog and Pug — breeds with the highest numbers of BOAS-affected dogs — asked the OFA to establish an RFG testing program and health-clearance database.

At the Rose City Cluster, 54 dogs — 19 Bulldogs, 23 French Bulldogs and 12 Pugs — had RFG screenings, and 52 percent received clinically unaffected grades of 0 or 1 for their OFA clearance certificates, says Jerold Bell, DVM, adjunct professor of genetics at the Cummings School of Veterinary Medicine of Tufts University and chair of the World Small Animal Veterinary Association (WSAVA) Hereditary Disease Committee.

The 48 percent of clinically affected dogs that received grades of 2 and 3 in RFG testing are considered to have a higher risk and high risk, respectively, of producing BOAS-affected puppies. Dogs with grade 3 respiratory function should not be bred, according to the RFG guidelines.

The increasing popularity of these breeds over the past several years is seen worldwide. In AKC registrations, the French Bulldog started its climb up the top 10 most popular breeds ladder in 2014. Bulldogs, ranked number six in 2022 for the second straight year, have been a top-10 breed since 2007. Pugs, the 35th most popular breed in 2022, have been among the top 20 percent for more than a decade.


Dr. Kathleen Ham of the University of Florida listens to the breathing of a French Bulldog following the exercise test.


The health chairs for the parent clubs despair that few AKC litter registrations in 2022 were by club members. They report that less than 2 percent of French Bulldog and Pug litters and about 4 percent of Bulldog litters were bred by club members.

In the U.K. in 2022, The Kennel Club registered 225 breeds and saw a return of the Labrador Retriever as the most popular breed, after three years of the French Bulldog being on top. In 2022, the Bulldog was ranked number eight, and the Pug was number 17.

In January 2023, the Netherlands became the first country in the world to ban ownership of French Bulldogs and Pugs, along with Persian and Scottish Fold cat breeds. Citing conformational extremes, the Dutch government said most dogs of these flat-faced breeds suffer from a range of serious disorders, as well as being chronically out of breath and susceptible to heat stroke.

Meanwhile, the WSAVA Hereditary Disease Committee has produced an informative video on BOAS featuring global veterinary experts (

“Due to the rapidly increasing popularity of short-nosed dogs and misguided government banning of breeding and owning these dogs, we are focusing on BOAS as a major project this year,” Dr. Bell says.

“Many have taken to breeding these dogs without carefully considering or being aware of the health and welfare consequences of extreme physical characteristics,” he continues. “The general public who looks to breed their short-nosed dogs must evaluate and screen their dogs for BOAS to select against producing affected dogs.”

The U.S. market value of puppies of these popular breeds varies geographically. The parent-club health chairs estimate that:

Pug puppies sold as companions go for $1,500 to $3,000, and those sold as prospective show dogs sell for $4,000 to $6,000

Bulldog puppies considered to be companions sell for $2,000 to $5,000, and show-quality Bulldog puppies go for $3,000 to $10,000

French Bulldog puppies sold as companions sell for $5,000, and those destined for show careers may sell for $10,000 to $20,000

Calvin Dykes, chair of the French Bulldog Club of America Health & Genetics Committee, says, “There are two things that proliferate the breeding of French Bulldogs: One is the breed’s popularity, and the other is the money breeders make selling puppies, whether they health-test or not.”

Embracing the parent club’s stewardship role, Brenda Belmonte, chair of the Pug Dog Club of America Health Fund Committee, says, “Our member breeders strive to preserve our breed’s unique traits while producing healthy Pugs through health testing. It is easy to place blame on one cross section of breeders, but we are all responsible for ensuring that our breed and the puppies we produce are able to live healthy, normal lives.

“I think the public’s perception is that all Pugs are afflicted with BOAS. Our health committee is working diligently to educate not only our member breeders but also the public at large,” she adds. “Pugs can and do compete successfully in a variety of dog sports. Being brachycephalic does not inherently mean unhealthy.”

Elizabeth Milam, co-chair of the Bulldog Club of America Health Committee, says the public is well aware of respiratory health concerns in Bulldogs. “The problem is the lack of awareness of all the normal-breathing dogs, of which there are plenty,” she says. “We have a successful education program and have made great strides over the past three decades, but find it nearly impossible to reach the 96 percent of non-member breeders.”

Here is a look at BOAS, respiratory function grading, and how health-focused breeding can be used to produce healthy brachycephalic dogs. 


Short-Nosed Breeds and BOAS


Brachycephalic comes from “brachy,” meaning short, and “cephalic,” meaning head. Anatomically, brachycephalic dogs have a shorter-than-normal skull, which gives them flat, wide-shaped heads. The shortened nose makes the soft tissue in the nose and throat of some dogs too large, which causes obstruction from their stenotic nares, or nostrils, to the trachea, or windpipe. Short-nosed dogs may breathe noisily and pant heavily as they struggle to breathe.

Although the Bulldog, French Bulldog and Pug have the highest numbers of BOAS-affected dogs, there are many other brachycephalic breeds predisposed to upper-airway obstruction. This includes the Affenpinscher, Boston Terrier, Boxer, Brussels Griffon, Bullmastiff, Cane Corso, Cavalier King Charles Spaniel, Chow Chow, Dogue de Bordeaux, English Toy Spaniel, Japanese Chin, Lhasa Apso, Mastiff, Pekingese and Shih Tzu.

“The clinical signs of BOAS are variable and can include noisy breathing, exercise intolerance, regurgitation and dysphagia, or difficulty swallowing,” Dr. Ladlow explains. “Airway-related subtle signs include excessive panting, sleep disorders and heat intolerance. Being overweight and obese worsen the condition across all breeds.”

BOAS manifests differently among breeds and individual dogs. Generally, “French Bulldogs tend to have narrow nostrils that may be nearly completely blocked, causing them to keep their mouth open to breathe,” Dr. Ladlow says. “Bulldogs have a very narrow windpipe that is essentially too narrow to get air in. Pugs have compressed and thickened nasal sinuses and long, soft palates, causing them to obstruct in their throat and top of the windpipe.”

Dr. Kelley Thieman of Texas A&M University performs an auscultation test on a French Bulldog at the first pilot screening in January 2022.


The exaggerated anatomical features of brachycephaly can cause other conformation-related diseases. Eye problems, including corneal ulcerations, may occur due to the shape of the eyes and extreme skin folds. Dental disease from a short muzzle and teeth overcrowding and chronic ear infections from tight ear canals are not uncommon. Chronic vomiting may occur from labored breathing. Dystocia, or difficulty giving birth, relates to puppies having large heads.

BOAS, however, is considered the most serious brachycephaly disorder because it can dramatically impair a dog’s ability to exercise, play, eat and sleep.

“There are many different surgeries performed on brachycephalic dogs with BOAS to improve their breathing,” says Kelley Thieman, DVM, MS, DACVS, small-animal associate professor and the Shaw Chair of Soft Tissue Surgery at Texas A&M University College of Veterinary Medicine and Biomedical Sciences.

“We perform an upper-airway examination to determine each dog’s specific abnormalities and what surgeries are needed,” she says. “The most common surgeries involve enlarging the nostrils, shortening and thinning the palate, and removing tissue at the level of the voice box, or larynx, that is present due to increased negative pressure from difficulty moving air.”

“These breeds did not historically have short noses,” says Peter Sandoe, PhD, professor of bioethics at the University of Copenhagen in Denmark, in the WSAVA video. “Rather, their short noses have evolved over numerous generations.”

“Some of the mutations associated with the shortened face are now fixed in the mutant form in each breed,” explains geneticist David Sargan, PhD, of the Cambridge University BOAS Research Group, in the WSAVA video. “We know that some members of each brachycephalic breed do not have BOAS, which shows that these mutations by themselves are not enough to cause the disease. However, studies show a correlation between more extreme traits and BOAS. Outcrossing to a different breed can revert these mutations.”

The health chairs for the Bulldog, French Bulldog and Pug parent clubs agree that outcrossing is not a goal to help them reduce BOAS disease incidence.

“We should be trying to revert BOAS through careful planned breedings, utilizing the testing we currently have available, including radiographs for tracheal hypoplasia, which is one aspect of BOAS, and having our breeding stock evaluated and graded using the RFG tool,” says Belmonte of the Pug Dog Club of America. “When we outcross with other breeds, we not only run the risk of introducing other health challenges, we may also lose the happy, playful nature of our breed.”

Milam of the Bulldog Club of America agrees. “It is absolutely unnecessary to outcross with a different breed. We see too many healthy dogs from a wide variety of bloodlines to even consider this extreme option.”


RFG: An Objective Airway Function Test


The respiratory function grading (RFG) tool currently is available for testing Bulldogs, French Bulldogs and Pugs, though 13 other brachycephalic breeds, of which 650 dogs already have been tested, are being evaluated by the BOAS Research Group at Cambridge University.

“We think some breeds will need the RFG scheme more than others,” Dr. Ladlow says. “Some brachycephalic breeds have very little BOAS in the U.K., so it will be breed-specific.”

In 2005, the research team began investigating how to objectively measure breathing function in brachycephalic breeds. When the RFG program was introduced in 2019 in the U.K., the obstructive airway syndrome was present in about 60 percent of tested Pugs, 50 percent of tested French Bulldogs and 45 percent of tested Bulldogs.

“We are waiting on the second and third generations to come through, and then we can see if we are nudging the populations,” Dr. Ladlow says. “The last update on the breeding of affected dogs was that 85 percent of breeders who had a grade 3 dog did not use the dog for breeding, which is excellent for both the welfare of the dog and the potential progeny.”

The RFG tests consists of four steps. Dogs can be tested starting at 12 months of age and must be retested every two years due to the progressive nature of BOAS. The clinical assessment involves:

A short health survey to learn information such as a dog’s age, sex, breathing function and clinical signs noticed by the owner

Initial physical examination while the dog is calm, including auscultation test, body temperature and body-condition score

Brisk three-minute exercise test designed to stress the upper airway

Post-exercise auscultation test to grade the dog on a scale of 0 to 3 based on respiratory function

“The exercise test increases the sensitivity of the BOAS diagnosis,” Dr. Ladlow says. “The slow trot is not intended to assess cardiovascular fitness — rather, to stress the upper airway, as dogs having a calm disposition may breathe quietly in a consult room but when placed under mild airway stress show marked signs of disease.”


Elizabeth Milam, co-chair of the Bulldog Club of America Health Committee, takes "Sugie," a 4-year-old female Bulldog, on the exercise test at the pilot screening. Sugie was considered to be clinically unaffected with BOAS.


The auscultation test distinguishes grade 0 dogs showing no evidence of BOAS and mildly affected grade 1 dogs — both of which would receive health clearances — from moderately affected grade 2 and severely affected grade 3 dogs. When airway noise is heard without a stethoscope, the dog is considered clinically affected.

Dr. Ladlow explains the breathing noises heard with the stethoscope gently positioned on the right side of a dog’s neck:

Stertor – Low-pitched vibration noise heard toward the top of the larynx

Stridor – High-pitched sawing noise heard over the larynx

Nasal stertor – Low-pitched nasal snort or vibration

Nasal stridor – High-pitched whistle, usually heard when a dog takes air in

RFG testing has been licensed to 11 countries, including the U.S. via the Orthopedic Foundation for Animals. Part of each country’s contractual agreement requires sharing testing results with The Kennel Club for research analysis to advance the international effort toward better breeding results. The data is shared with participating countries.

“The BOAS program fits well with the OFA mission of promoting the health of dogs,” says Fran Smith, DVM, PhD, DACT, president of OFA. “The OFA has invested significant support to be certain the guidelines for the testing and training of the evaluators is consistent with the procedure in the U.K. that was developed by Dr. Ladlow.”

Testing consistency among veterinary clinicians is key to the success of the RFG program. It relies on educating veterinarians on the signs of upper-airway obstruction and how to assess severity of disease so that a dog would score the same respiratory grade regardless of the evaluator.


RFG Breeding Recommendations, courtesy of The Kennel Club. Green: The lowest risk of breeding dogs affected by BOAS. Yellow: A higher risk of producing dogs affected by BOAS. Red: A breeding that has a high risk of producing dogs affected by BOAS. These breedings are not recommended, as BOAS has a serious impact on a dog's health and welfare. A breeding that may produce affected puppies should never knowingly be carried out.


In the U.S., the first veterinarians trained on RFG testing were Dr. Thieman of Texas A&M and Dr. Kathleen Ham, DVM, MS, DACVS, small-animal clinical associate professor and soft-tissue surgery service chief at the University of Florida College of Veterinary Medicine. Two pilot screenings in 2022 held at the Purina Event Center in Gray Summit, Missouri, equipped them to accurately perform RFG tests and to train other veterinarians on the program.

“We met with Dr. Ladlow multiple times prior to evaluating dogs,” Dr. Thieman says. “Once we had a good grasp, we performed pilot examinations and then met with her again to debrief. We’ve continued to repeat that process.”

Currently, there are seven veterinarians trained in the U.S. and Canada to perform the RFG screenings.

Eddie Dziuk, chief operating officer of OFA, concedes that the small number of veterinarians initially trained will limit accessibility to RFG screenings, though the goal is to hold several health clinics in 2023 and to increase the number of examiners.


Health-Focused Breeding


The hallmark of a responsible breeder is consideration of the qualities of the sire and dam in an effort to balance conformation, health, temperament and genetic diversity. Sadly, the popularity of brachycephalic breeds has turned out breeders unaware of the health and welfare consequences of producing BOAS-affected dogs and a dog-loving public unaware that the snorting sounds of a dog struggling to breathe are not normal.

“Health-focused breeding produces healthy puppies,” Dr. Ladlow says. “We need breeders to do RFG testing on their dogs and for the public to look for the results of these tests. If breeders do not have access to these tests, then they should assess whether their prospective breeding dogs can perform a brisk walk for several minutes without laboring to breathe or having noisy breathing caused by obstruction.

“If affected dogs are not used for breeding, then the breathing function of the next generation of dogs will improve. This will require losing a portion of the breed populations from breeding, but these are populous breeds, and the loss of BOAS- affected dogs from breeding will improve the overall health of the breeds.”


Leading the pilot screening for BOAS in January 2022 at the Purina Event Center are, front row, from left, Eddie Dziuk, OFA chief operating officer; Dr. Fran Smith, president of OFA, and Dr. Kelley Thieman of Texas A&M University. Back row, from left: Dr. Kathleen Ham of the University of Florida and Dr. Jerry Klein, AKC Chief Veterinary Officer.


Reflecting on the genetics of BOAS, Dr. Bell says, “It is not fully understood how BOAS is inherited, and it is not always predictable. Breeders should select dogs with less exaggerated anatomical features and never knowingly breed dogs that could produce affected puppies. The parents and puppies should breathe without obvious noise, have open nostrils and a functional muzzle. The issue is not being a short-nosed dog but not being bred by a health-focused breeder who has selected breeding dogs with normal breeding.”

The Bulldog, French Bulldog and Pug parent clubs are planning BOAS health clinics at their 2023 national specialties. They also are making plans to add RFG testing to their recommended breed health tests with the Canine Health Information Center, or CHIC. Through Meet the Breeds, their websites, educational seminars and health programs, these parent clubs aim to educate club members and the public about healthy brachycephalic dogs and responsible breeding.

Dykes of the French Bulldog Club of America worries about the challenges ahead for the parent club of America’s most popular breed.

“If club members do everything they can to improve the respiratory health of the breed through health testing and selective breeding, how can we possibly make a dent on BOAS when 98 percent of breeders may not even health test?” he asks.

Dr. Bell is optimistic that the international focus on BOAS is already making strides in helping to reduce the disease. “It is cruel to breed a BOAS-affected dog,” he says. “No dog should snore. All dogs should run and breathe freely. These dogs are our companions, and their lives depend on us. All dogs deserve to live healthy lives.”




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