The researchers examined 102 English bulldogs: 87 from the United States and 15 from other countries. The dogs were genetically compared with an additional 37 English bulldogs presented to UC Davis veterinary clinical services for health problems. All were found to have very low genetic diversity, which can result from inbreeding.
Pedersen and his team explained that the breed began with a founding population of just 68. On top of that, breeding since the 1800s has artificially kept population sizes in check. This has caused additional reductions to the English bulldog's genetic diversity.
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In the United States, the English bulldog is perhaps best known as the mascot of the University of Georgia. Because of that iconic status, the dogs are particularly popular in the Southeast.
The terminology gets a bit confusing, as sometimes the terms English bulldog, American bulldog and just plain bulldog are used interchangeably. The American Kennel Club recognizes "bulldogs" and "French bulldogs."
The United Kennel Club (UKC), however, separately lists all of these breeds, and includes a newer one called the olde English bulldogge. Despite the spelling of its name, the olde English bulldogge was actually the product of a breeding project initiated in 1971.
"The revival of a healthy dog with the longevity to live well into its teens is a primary goal," according to a UKC fact sheet on the olde English bulldogge.
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This project and other efforts to breed the English bulldog with other breeds could improve the dogs' health. Many breeders, however, feel that any deviations from the original standard will produce dogs that are not true English bulldogs.
In the meantime, the dogs' health problems appear to be worsening.
As Pedersen said, "These changes (due to breeding) 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," he added, "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."