Tag Archives: brachycephalic

No simple way of predicting breathing difficulties in pugs, French bulldogs and bulldogs from external features

As many as a half of all short-nosed dogs such as pugs, French bulldogs and bulldogs experience breathing difficulties related to their facial structure. However, research published by the University of Cambridge suggests that there is no way to accurately predict from visible features whether an apparently healthy pug or French bulldog will go on to develop breathing difficulties.

The findings have implications for attempts to ‘breed out’ this potentially life-threatening condition.

French bulldog.jpg

Pugs and bulldogs have become popular breeds in recent years – the French bulldog is set to become the UK’s most popular canine, according to the Kennel Club. However, a significant proportion are affected by a condition known as Brachycephalic Obstructive Airway Syndrome (BOAS) related to their head structure.

Studies suggest that for over half of such dogs, BOAS may lead to health problems, causing not just snoring but also difficulty exercising and potentially overheating. It can even prove life-threating. But as symptoms often do not arise until after the dog has begun breeding, veterinary scientists have been searching for markers that can predict whether a dog is likely to develop breathing difficulties – and hence potentially help breed out the condition.

A study in 2015 led by researchers at the Royal Veterinary College, University of London, working across many breeds suggested that dogs whose muzzles comprised less than half their cranial lengths and dogs with thicker neck girths were at increased risk of BOAS. However, this new study suggests that these measures applied to individual breeds are not dependable for this purpose.

The Cambridge researchers took external measurements of features of head and neck shape, and of the external appearance of nostrils, together with measurements of body size and body condition score (an approximation to the degree of fatness/obesity) in just over 600 pugs, bulldogs and French bulldogs, the most numerous breeds that show this problem. Each of the dogs had also been graded objectively for respiratory function.

The team found that while the external head measurements did have some predictive value for respiratory function, the relationship was not strong, and the measurements that showed the best predictive relationship to BOAS differed between breeds. They were unable to reproduce conclusively the findings from the previous study by the Royal Veterinary College in any breed.

“It can be incredibly difficult to take measurements such as distance between eyes or length of nose accurately, even for experienced vets, as the dogs don’t keep still,” says Dr Jane Ladlow, joint lead author. “This may explain why it is so difficult to replicate the findings of the previous study or find any conclusive markers in our own.”

Neck girth was a slightly more reproducible measurement, and larger neck girth in comparison to chest girth or neck length was associated with disease in the bulldogs and French bulldogs. In male bulldogs, neck girth showed a close enough association with disease to give moderately good predictive accuracy for the presence of clinically significant BOAS.

The best measure identified by the Cambridge team was the degree of nostril opening, which proved a moderately good predictor of the presence and severity of BOAS in pugs and French bulldogs, and was also a useful marker for disease in bulldogs.

Altogether the variables measured, when combined, gave an 80% accuracy in predicting whether or not dogs will have BOAS, the difficulty of taking some of the measurements accurately, and the need to make multiple measurements and combine them in order to produce a prediction means that the researchers would not recommend using them as a guide to breeding.

Dr Nai-Chieh Liu, first author of the study, says: “Breeding for open nostrils is probably the best simple way to improve these breeds. Dog breeders should also avoid using dogs with extremely short muzzles, wide faces, and thick necks. These traits are all associated with increased risk of having BOAS.”

Joint lead author Dr David Sargan adds “At this moment there is no conclusive way of predicting whether any individual pug or bulldog will develop breathing difficulties, so we are now looking for genetic tests that may help breeders get rid of BOAS more rapidly.

“The best advice we can give to owners of short-nosed dogs is to make sure you get your dog checked annually for any potential difficulties in breathing, even if you have not yourself observed any in your dog, and to keep your dog fit and not let it get fat.”

Source:  University of Cambridge media release

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DNA influences face shape

A study of dog DNA has revealed a genetic mutation linked to flat face shapes such as those seen in pugs and bulldogs.

The research reveals new insights into the genes that underpin skull formation in people and animals.  Scientists say their findings also shed light on the causes of birth defects that affect babies’ head development in the womb.

Researchers at the University of Edinburgh’s Roslin Institute analysed DNA samples from 374 pet dogs of various pedigree and mixed breeds. The dogs were being treated at the Royal (Dick) School of Veterinary Studies.

All of the animals underwent body scans as part of their care, producing detailed 3-dimensional images of the dogs’ heads.  These high-resolution images — called CT scans — enabled the researchers to take precise measurements of the shape of the dog’s skull.

By comparing the dogs’ genetic information with measurements of their skulls, the team were able to pinpoint DNA variations that are associated with different head shapes.

One variation — found to disrupt the activity of a gene called SMOC2 — was strongly linked to the length of the dog’s face. Animals with the mutation had significantly flatter faces, a condition called brachycephaly.

Babies are sometimes born with brachycephaly too, though little is known about its causes. Scientists say screening children for changes in the SMOC2 gene could help to diagnose the condition.

Lead researcher Dr Jeffrey Schoenebeck, of the University’s Roslin Institute, said: “Our results shed light on the molecular nature of this type of skull form that is so common and popular among dogs.”

Source:  University of Edinburgh news

Anatomy 101: brachycephalic dogs

I was at a lunch last week and I was talking about brachycephalic dogs.  One fellow asked, ‘brachy what?’

Brachycephalic dogs are dogs with a short muzzle and generally flat face.   “Brachy” means “shortened” and “cephalic” means “head.”

These features make them very cute. But, this head structure doesn’t leave a lot of room for the nasal passages and palate, which are parts of the anatomy that help breathing.

Most of us who either own a brachycephalic dog or who have seen one at the dog park or elsewhere can identify the ‘brachy snort’ – the sound of a dog that is struggling to breathe.

We all know that dogs help to control their temperature on hot days through panting.  Unfortunately, brachycephalic dogs are inefficient panters and so these dogs are more susceptible to heat stroke.  They are generally not good outdoor dogs during summer because of this.

Some dogs also suffer from brachycephalic airway syndrome.  This syndrome is actually a group of upper airway abnormalities.  Brachycephalic syndrome is also known as congenital obstructive upper airway disease and in extreme cases, a veterinary surgeon may do surgery to help correct the abnormalities.

The abnormalities associated with the syndrome include:

  • stenotic nares, which are nostrils that are narrowed
  • elongated soft palate, which is a soft palate that is too long for the mouth and so the length partially blocks the entrance to the back of the throat
  • a hypoplastic trachea, an abnormally narrow windpipe
  • nasopharyngeal abnormalities,  the bone in the dog’s nasal cavity grows incorrectly and this can stop air flow.  This bone helps direct airflow and also helps with heating and humidifying inhaled air.

Because of their breathing difficulties, a brachycephalic breed must be fit and trim no matter what their life stage.  Obesity is a real threat to these dogs.

Since breathing difficulties become worse with strenuous exercise, it’s critically important to balance the dog’s caloric intake with their exercise and look for small opportunities to exercise the dog without causing stress.

Common brachycephalic dog breeds include:

·         English Bulldog

·         Pug

·         Shih Tzu

·         Pekingese

·         Boston Terrier

·         Cavalier King Charles Spaniel

·         Shar Pei

·         Lhasa Apso