Tag Archives: breeding

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

Scientists warn about health of English Bulldog

According to new research it could be difficult to improve the health of the English bulldog, one of the world’s unhealthiest dog breeds, from within its existing gene pool. The findings will be published in the open access journal Canine Genetics and Epidemiology.

The English bulldog’s limited genetic diversity could minimize the ability of breeders to recreate healthy phenotypes from the existing genetic stock, which were created by human-directed selection for specific desired physical traits.

English Bulldog

Many large regions of the bulldog’s genome have been altered to attain the extreme changes in its outward appearance. This includes significant loss of genetic diversity in the region of the genome that contains many of the genes that regulate normal immune responses. Despite this, the English bulldog is one of the most popular dog breeds, particularly in the US, where the bulldog was the fourth most popular pure breed in 2015.

Lead author, Niels Pedersen from Center for Companion Animal Health, University of California, US, said: “The English bulldog has reached the point where popularity can no longer excuse the health problems that the average bulldog endures in its often brief lifetime. More people seemed to be enamoured with its appearance than concerned about its health. Improving health through genetic manipulations presumes that enough diversity still exists to improve the breed from within, and if not, to add diversity by outcrossing to other breeds. We found that little genetic ‘wiggle room’ still exists in the breed to make additional genetic changes.”

Pedersen adds: “These changes have occurred over hundreds of years but have become particularly rapid over the last few decades. Breeders are managing the little diversity that still exists in the best possible manner, but there are still many individuals sired from highly inbred parents. Unfortunately eliminating all the mutations may not solve the problem as this would further reduce genetic diversity. We would also question whether further modifications, such as rapidly introducing new rare coat colors, making the body smaller and more compact and adding more wrinkles in the coat, could improve the bulldog’s already fragile genetic diversity.”

This is the first broad-based assessment of genetic diversity in the English bulldog using DNA analysis rather than pedigrees. DNA analysis is needed to measure, monitor and maintain genetic diversity. This has been done in several other breeds including Standard and Miniature Poodles, American Golden Retrievers, and American and European Italian Greyhound.

The researchers sought to identify whether there is enough genetic diversity still existing within the breed to undertake significant improvements from within the existing gene pool. The researchers examined 102 English bulldogs, 87 dogs from the US and 15 dogs from other countries. These were genetically compared with an additional 37 English bulldogs presented to the US Davis Veterinary Clinical Services for health problems, to determine that the genetic problems of the English bulldogs were not the fault of commercial breeders or puppy mills.

Many Swiss breeders have started to outcross the breed with the Olde English Bulldogge (an American breed) to create the Continental Bulldog, hoping to improve the breed’s health. Although outcrossing the English bulldog could improve its health, many breeders feel that any deviations from the original standard will no longer be an English bulldog.

The breed started from a relatively small genetic base with a founder population of 68 individuals after 1835 and has undergone a number of human created artificial bottlenecks (drastic reductions in population size). These could also have greatly diminished genetic diversity.

Source:  BioMed Central media release

The genetics behind cleft lip and palate in dogs

Scientists studying birth defects in humans and purebred dogs have identified an association between cleft lip and cleft palate – conditions that occur when the lip and mouth fail to form properly during pregnancy – and a mutation in the ADAMTS20 gene.

“These results have potential implications for both human and animal health, by improving our understanding of what causes these birth defects in both species,” said Zena Wolf, BS, a graduate student at the University of California, Davis School of Veterinary Medicine.

Lentil, a French Bulldog born with cleft lip and palate.  Photo by CNN.  Read more about Lentil's story here

Lentil, a French Bulldog born with cleft lip and palate. Photo by CNN. Read more about Lentil’s story here

In both humans and dogs, cleft lip and cleft palate occur naturally with varying degrees of severity, and can be caused by various genetic and environmental factors. Since purebred dogs breed only with each other, there is less genetic variation to consider, making cleft lip and cleft palate easier to understand in these populations, Ms. Wolf explained.

From previous studies, the researchers knew that a mutation in the dog genes DLX5 and DLX6, which are involved in face and skull development, explained 12 of 22 cases of cleft palate. However, a mutation in the corresponding human genes accounted for just one of 30 cases in the study sample.

To search for additional genes that may be involved, Ms. Wolf and colleagues performed a genome-wide association study (GWAS), a study that compares the genomes of dogs with cleft lip and cleft palate to those of dogs without it. They found that the conditions were associated with a mutation in the gene ADAMTS20 that caused the protein it encodes to be shortened by 75 percent. Previous studies had shown that ADAMTS20 is involved in the development and shaping of the palate, but no specific mutations that occur in nature had been identified. A similar GWAS in people with cleft lip and cleft palate suggested that mutations in the human version of the ADAMTS20 gene may also increase the risk of these conditions.

“Cleft lip and cleft palate are complex conditions in people, and the canine model offers a simpler approach to study them,” Ms. Wolf said. “Not only does this research help people, but it helps dogs, too,” she added.

Future directions include searching for additional genes that may be associated with cleft lip and cleft palate, and extending the research to other breeds of dogs, such as Labrador Retrievers and Whippets.

Source:  The American Society of Human Genetics press release

 

Domestication Syndrome

More than 140 years ago, Charles Darwin noticed something peculiar about domesticated mammals. Compared to their wild ancestors, domestic species are more tame, and they also tend to display a suite of other characteristic features, including floppier ears, patches of white fur, and more juvenile faces with smaller jaws. Since Darwin’s observations, the explanation for this pattern has proved elusive, but now, in a Perspectives article published in the journal GENETICS, a new hypothesis has been proposed that could explain why breeding for tameness causes changes in such diverse traits.

Photo courtesy of Lucky Dog Animal Rescue

Helios, an approximately 3-year-old cattle dog/greyhound mix with Lucky Dog Animal Rescue. Photo courtesy Lucky Dog Animal Rescue

The underlying link between these features could be the group of embryonic stem cells called the neural crest, suggests the research team.

“Because Darwin made his observations just as the science of genetics was beginning, the domestication syndrome is one of the oldest problems in the field. So it was tremendously exciting when we realized that the neural crest hypothesis neatly ties together this hodge-podge of traits,” says Adam Wilkins, from the Humboldt University of Berlin – one of the study’s authors.

Neural crest cells are formed near the developing spinal cord of early vertebrate embryos. As the embryo matures, the cells migrate to different parts of the body and give rise to many tissue types. These tissues include pigment cells and parts of the skull, jaws, teeth, and ears—as well as the adrenal glands, which are the center of the “fight-or-flight” response. Neural crest cells also indirectly affect brain development.

In the hypothesis proposed by Wilkins and co-authors Richard Wrangham of Harvard University and Tecumseh Fitch of the University of Vienna, domesticated mammals may show impaired development or migration of neural crest cells compared to their wild ancestors.

“When humans bred these animals for tameness, they may have inadvertently selected those with mild neural crest deficits, resulting in smaller or slow-maturing adrenal glands,” Wilkins says. “So, these animals were less fearful.”

The authors also suggest that the reduced forebrain size of most domestic mammals could be an indirect effect of neural crest changes, because a chemical signal sent by these cells is critical for proper brain development.

The hypothesis will require testing, which will be able to be done once genetic mapping of domesticated species like the dog, fox and rat are completed.

Full journal article details:  The “Domestication Syndrome” in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics
Adam S. Wilkins, Richard W. Wrangham, and W. Tecumseh Fitch. GENETICS July 2014, 197:795-808, doi: 10.1534/genetics.114.165423
http://www.genetics.org/content/197/3/795.full

Source:  Genetics Society of America media release

 

When a poodle isn’t a poodle

Poodle vs ferret

Last month, a story circulated worldwide about a man in Argentina who had purchased what he thought was two toy poodles from a local market for a bargain price.  The poodles turned out to be ferrets that had been loaded with steroids to plump them up and make them appear more like a poodle than a ferret.

I have two things that concern me:

1.  While some people focused on debates about ‘how dumb could the guy be….?’, my thoughts were – ‘what a shocking case of abuse.’

These ferrets were loaded with damaging steroids to make money.  There was no thought given to their welfare and the impacts on their health from the steroids.

2.  There is no such thing as a free lunch.  If something sounds too good to be true, it probably is…

When dealing with animals, people really need to think about quality.  Are they buying quality?  Is it a cheap product that could damage animal health (how many cases have we seen with cheap, spot-on flea treatments and the damage that they cause?)

In this case, the buyer should have questioned the bargain price.  At a minimum, he was probably purchasing a poodle with health problems resulting from poor breeding practice.  What he got was even worse, a different species of animal that had been altered to deceive…

So, in summary, I think it is good that this story was circulated.  However, I am disappointed the track that many media took about the story.    We need to put animals first.  Welfare of the animals is top priority.

What do you think?