New research confirms what a lot of pet owners have suspected for ages: Labrador retrievers tend to be more food-obsessed than other breeds.
The reason is that Labrador retrievers sometimes have a mutation of a gene called POMC that leads to greater food-motivated behaviors, according to a study in the journal Cell Metabolism. It is the first gene ever discovered that is associated with canine obesity.
"Whenever there's something more common in one breed than another, we think genetics are involved," co-author Eleanor Raffan, a veterinary surgeon and geneticist at the University of Cambridge, said in a press release. She previously studied human obesity before investigating the canine angle.
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Raffan and her team first looked at the genes of 15 obese and 18 lean Labrador retrievers. The researchers noted a variation of POMC in many of the overweight dogs. For these canines, the POMC gene looked "scrambled at the end," they said, hindering the dog's ability to produce compounds that are usually involved in switching off hunger after a meal.
In humans, common variations in the POMC gene have been associated with weight gain and reduced feelings of satiation.
Senior author Stephen O'Rahilly, co-director of the Wellcome Trust-Medical Research Council Institute of Metabolic Science, said, "There are even some rare obese people who lack a very similar part of the POMC gene to that which is missing in the dogs."
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The researchers next analyzed a much larger number of dogs: 310 Labrador retrievers. Not all of the dogs with the DNA variation were obese, and some were obese without having the mutation, but the POMC deletion was nonetheless associated with greater weight.
According to an owner survey, these same dogs were also more food-motivated, meaning they frequently begged their owners for food, paid greater attention at mealtimes, and scavenged for scraps more often. On average, the genetic mutation was associated with about a 4.5-pound weight increase in the dogs.
"We've found something in about a quarter of pet Labradors that fits with a hardwired biological reason for the food-obsessed behavior reported by owners," Raffan said.
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She added that there were plenty of food-motivated dogs in the study that didn't have the mutation, "but there's still quite a striking effect."
The team looked at yet another group of Labs, totaling 411, and found that roughly 23 percent of them have the noted genetic mutation. The mutation might not be all bad news, though. It might even make dogs easier to train, since they respond so well to food rewards.
The researchers determined that the mutation was markedly more common in 81 assistance Labrador retrievers that were included in the study. The POMC deletion occurred in 76 percent of these dogs.
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"It was surprising," Raffan said. "It's possible that these dogs are more food-motivated and therefore more likely to be selected for assistance-dog breeding programs, which historically train using food rewards."
The researchers hope to study puppies in the future to see if those more likely to be selected for assistance dog training indeed have the genetic mutation. They also want to learn more about the impact of POMC mutations, and how the hardwiring could further affect the health of both dogs and humans.
Raffan had this to say to owners of Labrador retrievers, who might feel exasperated at times with their often ravenous pets: "You can keep a dog with this mutation slim, but you have to be a lot more on-the-ball."
"You have to be more rigorous about portion control," she added, "and you have to be more resistant to your dog giving you the big brown eyes. If you keep a really food-motivated Labrador slim, you should give yourself a pat on the back, because it's much harder for you than it is for someone with a less food-motivated dog."