If your Labrador retriever seems to have a bottomless stomach, there might be a scientific reason behind it.
These dogs are well-known among vets for their tendency to pile on the pounds. Previous research has shown that a quarter of Labradors—and two thirds of a less common breed called flat-coated retrievers—carry a genetic mutation linked to obesity in other animals. New experiments have revealed that dogs with this mutation not only feel hungrier between meals but also burn less energy than their counterparts.
“The dogs seem to be receiving a molecular starvation signal,” says Eleanor Raffan, a vet and geneticist at the University of Cambridge and co-author of the new paper published on March 6th in Science Advances. “As a result, they try to eat more and reduce their energy expenditure.”
Labrador Retrievers: Investigating the POMC Mutation
In the new study, Raffan and her colleagues aimed to understand how the mutation, which affects a gene called pro-opiomelanocortin (POMC), impacts the lives of dogs carrying it. They recruited dozens of dog owners in the UK who were willing to participate in a series of experiments.
The first experiment, nicknamed the “sausage in a box” test, involved bringing Labs into the lab around three hours after breakfast. The researchers showed each dog a sausage before placing it in a plastic box with holes, allowing the dog to smell but not eat the treat. They then observed how the dogs interacted with the box and for how long. The experiment revealed that dogs with the POMC mutation were more fixated on the sausage box, spending roughly twice as much time trying to interact with or manipulate it.
The researchers also involved dog owners in a home experiment. Breakfast became an all-you-can-eat buffet, with dogs receiving a new tin of food every 20 minutes until they stopped eating, vomited, or reached the experiment’s limit of 6.5 pounds of food. On average, all the dogs, regardless of whether they had normal POMC genes, consumed roughly four pounds of food—”a tremendous amount,” says Raffan. (However, dogs with the POMC mutation ate slightly more, and those without it were more likely to end the experiment by vomiting.) The results suggest that the mutation doesn’t affect how quickly dogs feel full. However, the increased focus on food by the POMC mutation group suggests these dogs would continue to seek out more food if it wasn’t readily available, perhaps through begging or stealing.
Labrador Retrievers: Lower Energy Burning
The researchers also investigated the other side of the equation: how dogs burn energy. For this experiment, they recruited 19 flat-coated retrievers (these dogs carry the POMC mutation more frequently than Labradors). They wanted to compare dogs with no mutation at all to dogs with the mutation in both copies of the gene, expecting more subtle results. Dog owners encouraged their pets to fall asleep in a chamber that measured the metabolic gases they produced. This allowed the researchers to calculate how much energy they burned while resting. The scientists found that dogs with the POMC mutation used less energy than their counterparts.
A Double Whammy
Taken together, the experiments demonstrate the complex way the mutation affects a dog’s brain and body, says Raffan. It makes them crave food more without necessarily making them like a particular food more or needing more food to feel full. At the same time, it makes them burn food more slowly. “They’re hit with a double whammy of both eating more and burning fewer calories, meaning they’re predisposed to obesity from both directions,” says Raffan.
Labrador Retrievers: Legacy of an Extinct Breed
The mutation is a legacy of a now extinct breed called St. John’s water dogs, the ancestor of both Labradors and flat-coated retrievers. These dogs accompanied fishermen in the 16th and 17th centuries, happily retrieving fish from the frigid waters off Canada’s maritime provinces. “In that context, you can imagine that being willing to eat anything you could find and having a bit of a layer of blubber to keep you warm in the sea might have actually been quite a good idea and a bit of an advantage for those dogs,” says Raffan.
Combating Obesity
However, for modern pets, the mutation is more detrimental because obesity can cause or worsen health problems ranging from breathing difficulties to skin conditions to incontinence, says Raffan. One survey found that 11 percent of Labradors were obese, compared to 7 percent of non-Labradors. Another survey showed that 5 percent of Labradors were obese, and 36 percent.
Artificial Intelligence assisted in compiling this article.
