The English bulldog's flat face and adorable skin folds are just a couple of its distinctive traits. But these same features that make owners go gaga also cause a number of health problems, leading people to wonder whether these dogs could be bred to be healthier.
But a new study finds that boosting the dog breed's health could be difficult, particularly if breeders don't cross the English bulldog with another breed. The study found that there's not much genetic diversity within the English bulldog population, which will make it hard to improve their health without going outside the breed to bring new genes into the mix.
"The English bulldog has reached the point where popularity can no longer excuse the health problems that the average bulldog endures," study co-author Niels Pedersen, of the University of California, Davis' School of Veterinary Medicine, said in a statement. "Improving health through genetic manipulations [breeding] presumes that enough diversity still exists to improve the breed from within," Pedersen said. However, "We found that little genetic 'wiggle room' still exists in the breed to make additional genetic changes," he added. [The 10 Most Popular Dog Breeds]
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The features of today's English bulldog arose from hundreds of years of breeding, but changes to the breed's traits have become particularly rapid in recent decades, Pedersen said. The dogs have been bred for traits that are desirable to people: a flat face, a short nose, skin folds and a "child-like" appearance and personality, the researchers said.
But many of these same features also give rise to health problems. The dogs' head structure makes it harder for the animal to pant, which can cause the dog to overheat easily in hot weather and make it difficult for the dog to exercise. The breed is also predisposed to skeletal problems that make it very difficult for English bulldogs to conceive and give birth naturally. In addition, the skin folds make the dogs susceptible to dermatitis (skin inflammation) and certain eye conditions. The English bulldogs' genetics also make them prone to autoimmune disorders and other immune system problems, the researchers said.
In the new study, the researchers wanted to determine whether there was enough genetic diversity within the English bulldog breed to make improvements to the dogs' health from within the existing gene pool. Genetic diversity refers to the variety of genes within a population.
They analyzed the DNA of 102 English bulldogs, mostly from the United States. They also included 37 bulldogs that had recently visited the vet because of health problems, to determine whether the genes of "sick" bulldogs were significantly different from those of the other dogs.
The study confirmed that the English bulldog population has low genetic diversity, which is the result of breeding that was highly focused on certain traits, the researchers said.
The loss of genetic diversity was particularly severe in a region of the genome that regulates normal immune response, the researchers said. And ongoing attempts to breed English bulldogs so that they have new coat colors and a more compact body type could actually reduce genetic diversity even further, they said.
One way to reduce the health problems of English bulldogs might be to breed them with other dog breeds, the researchers said. Indeed, some breeders have started to cross the English bulldog with an American breed called the Olde English Bulldogge to create the Continental Bulldog, in hopes of reducing the breed's health problems. However, many breeders feel that any significant changes from the current standard in the breed would mean that the resulting dogs would no longer be English bulldogs, the researchers said.
The study is published today (July 28) in the journal Canine Genetics and Epidemiology.
Original article on Live Science.
