The problem with pedigree

18 July 2016

Interview with

Jane Ladlow, Cambridge University

During the Victorian times humans started selecting for much more extreme Bulldoglooks and sizes for our dogs - creating so called 'pedigrees'. But this has caused problems: it has resulted in some breeds having extreme features, like short legs or long bodies, that can affect their quality of life, and what's more - when you breed from a narrow gene pool, genetic defects or inherited disease become common and widespread. And while people fork out a fortune for a pedigree dog, each breed has its own set of problems they are likely to suffer from, such as tumours, arthritis or breathing problems. Georgia Mills wanted to know more about one such disease - one suffered by pugs and bulldogs,  which causes them to struggle breathing, so went to Cambridge Veterinary school, to meet Jane Ladlow, who is investigating this disease and trying to set about solving it...

Jane - The disease that we are interested in is Brachycephalic Obstructive Airway Syndrome - that seems to be an issue in the smaller dogs that have the very, very short faces. So we look at the three extreme brachycephalic dog and we think of these as the pug, the bulldog, and the French bulldog. And they've been bred to look very appealing to people and they way they do this is they make the nose shorter, larger eyes, and a little bit more like a human baby face. They have become exceptionally popular in the last few years. So it used to be that you'd expect to see 4 or 5,000 particularly French bulldogs around and now you will see 10 times that amount so a very, very, popular breed.  And that means you're starting off with quite a small number of breeding stock and that your using them more and we're also getting more dogs in from different countries and we're not sure about their health. So it's a population explosion that is causing quite a lot of the problems we're seeing.

Georgia - And what are these problems causing for the dogs?

Jane - We look particularly at the breathing, and what's happened in some of these dogs is as their skull has reduced in it's length, the soft tissues within the skull have not reduced in the same way and this means they have areas of obstruction in their upper airway and you can hear this. Many people think it's normal to hear a bulldog snorting as it walks past you, but that indicates there are levels of obstruction in that airway.

Georgia - That's horrible! So all this soft tissue is crammed into this much smaller space meaning the air just finds it really hard to get through?

Jane - Exactly - that's exactly it.

Georgia - This is something you study here. How are you looking into this?

Jane - We started quite a few years ago now. So the problem with this disease is that it's a very difficult disease to measure. Doing functional breathing tests on dogs is more complicated than humans because they won't cooperate in the same way. With humans you can say breath into this tube and you can get spirometer readings but with dogs, if you handle them or put a face mask on them, you can alter their breathing. So unless you can actually measure what a normal dog is like, and what an affected dog is like, then you can't really determine how many dogs are affected, and how badly they're affected. And also, for me, I had no real idea how well these dogs were responding to treatment.

Now we used to look at owner questionnaires, and owner questionnaires are useful but many owners don't recognise the disease symptoms in their dogs. So there has been some work done that has shown 60% of owners do not really recognise the signs of obstructive airway disease

We tried lots of different techniques: we tried  a treadmill and that wasn't very good because bulldogs went off the end, and we tried putting tapes round them to measure how their respiratory functions alter in the thoracic wall in the abdomen, but many of our dogs are barrel chested and the tapes move. So, after trying lots of different ways of trying to measure respiratory function in these dogs, we came up with a new technique which we call plethysmography - whole body plethysmography.

Georgia - Jane showed me the kit they used for this technique. There's a clear plastic box with a comfy doggie bag inside. The dog settles down in the box and the pressure changes inside are measured and recorded on a laptop. This then shows how much air the dog can get in and out of their lungs and how efficiently. I wanted to see the box in action so we recruited willing bulldog Ronnie...

Hello! Hello! No don't eat the microphone! Oh you are friendly and a bit smelly!

Jane - We did have one dog that we used to have a temperature probe in the chamber and one dog ate it. So all our probes now are outside the chamber...

Georgia - Once Ronnie had settled down in the box, we could watch his breathing traces in real time. This technique has allowed Jane and her team to quantifiably estimate how bad an individual case may be. And after testing over 800 dogs, it looks like up to 60% of pugs and 50% of bulldogs have this disease, which isn't good.

Jane - Unfortunately we're not sure what proportion of animals die from Brachycephalic Obstructive Airway Syndrome because they are often just recorded as acute deaths.  And it's also reported as heat stroke because another thing these animals can't do if you're not panting and breathing effectively, then you're not cooling yourself down properly.  So it's often put down as acute death or heat stroke, but certainly a proportion of them would be exasperated by their respiratory obstruction.

Georgia - Ah because yes, dogs can't sweat can they - they lose it all through panting?

Jane - Yes, so panting is vital and this is why you will hear a lot of information about not taking out Brachycephalics in the heat of the day, which is sensible, but it's a little bit of  shame that we have to look after them so carefully because they have breathing issues.

Georgia - What else can we do about this?

Jane - Well, if you have an affected dog, then we can manage the disease in a number of different ways. So we can be careful about when we exercise, we can use coats that keep the animals cool, and then for dogs that require more help we have surgical procedures.

The other thing that we are looking at in the longer term; we have Dr David Sargan working on the genetics of this disease and we are hopeful that in the future the geneticists may be able to offer some guidance to the breeders. I don't think it will be simple yes or no affected tests, but it might be an estimated breeding value where you could look at a couple of dogs and you can say, ok well if you breed this particular dog with this particular dog then your odds of having affected progeny are so much, and that will at least give breeders a lot more of an idea of how to improve the health of the breed. So I think longer term we do need to look at trying to support the breeds and improving the health.

The other discussion is whether we bring some different blood into some of these breeds, which is a very difficult question because for a number of the pug breeders, it's the pugs we're particularly thinking of, it's a very emotive area that you shouldn't really change the breed, but maybe that's a faster way to improve the breathing.  But these are questions that the Kennel Club will have to think about.

Georgia - Should people who care about animal welfare buys pugs and bulldogs if this is such a big problem?

Jane - I think you have to be exceptionally careful where you get a brachycephalic dog from. So if I was going to buy a brachycephalic dog, I would go and I would look at the mother;  I would ask to look at the father and have some idea of their breathing. I wouldn't just want photo's I'd actually want to go and visit the parents. I'd want to see some other bulldogs, or French bulldogs, or pugs that have been produced by those breeders, and I'd like to see the dogs exercising and having a normal life. There are good dogs out there. However, unless you're going to do your homework very carefully, you do have a risk of having a dog that has this horrible problem.


I agree with everything Jane has laid out, especially conscientious purchasing of such animals if owners are planning to add one to their family. Prevention is much better than cure, although currently finding an athletic brachycephalic dog with minimal BOAS related problems is like searching for gold. Ethical breeding practices are the way forward, with consideration of outcrossing to improve genetic diversity. The latter has to be considered very carefully though as there are risks of bringing in non-conformational diseases from outwith the brachycephalic breeds. Nevertheless these dogs do not deserve to have such a basic function (breathing) compromised.

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