Lab Retrievers Hardwired to Crave Food
Labrador retrievers have a genetic mutation that causes them to be more food-obsessed than other dogs.
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.
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."
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.
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.
"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."
DNA analysis, as well as historical information, is helping to reveal the world's most ancient dog breeds. A new study, published in the journal Proceedings of the Royal Society B, puts the spotlight on East Asia as being a primary origination point for dog domestication. The earliest known dog-like fossils come from Europe, but it is likely that these dogs did not produce large populations that led to distinctive breeds. Genetic research on existing dogs reveal that certain breeds stand apart from others. "Our results show that these breeds represent lineages older than modern European breeds, and in this sense can be considered as ancient," senior author Wiesław Bogdanowicz of the Polish Academy of Science's Museum and Institute of Zoology, told Discovery News. Afghan hounds fall into the ancient group. In fact, they were called "ancient" long before the advent of genomics. In 1925, an article published in "The Dog Fancier" had the declarative title: "The Afghan Hound Is an Ancient Breed." Canine experts at the time even thought that the dogs "entered the ark with Noah" and were the world's first ever dogs. According to the historical record, Afghan hounds date back to the pre-Christian era of northeastern Afghanistan. The original name for the breed, famous for its silken coat and fashion model thin build, was "Tazi."
Basenjis look remarkably like dogs featured in ancient Egyptian art. Drawings found in the tombs of the 2700 B.C. Great Pyramid of Khufu show such dogs seated near the feet of their owners, or under chairs. The cat-loving Egyptians might have taken to the dogs because, like felines, these canines tend to be relatively quiet and wash themselves regularly with their tongues. Most researchers, including Bogdanowicz and his team, still believe that domesticated dogs largely arose in Asia and migrated to other regions. "It is very likely that migrating populations of early farmers were followed by dogs," he said, explaining that these dogs were not feral, but were originally free-breeding. Basenjis possess a very distinctive suite of characteristics, which must have been maintained by human breeders. While the official breed only dates back 60 years, these dogs clearly have been in existence for centuries.
Nearly all DNA studies of dogs find that Arctic breeds, such as the Alaskan malamute, stand apart from modern breeds. An extensive genomic investigation conducted by senior author Robert Wayne from the University of California at Los Angeles and colleagues found that Alaskan malamutes, as well as American Eskimo dogs and Siberian huskies, "are highly divergent from other dog breeds." This means that they have evolved on a slightly different path than other, more modern dogs. Wayne and his team added that "historical information suggests that most have ancient origins, greater than 500 years ago."
"Saluki" is thought to derive from two early Sumerian words meaning "plunge-earth." What that means exactly, in reference to the dogs, remains a mystery, but it is known that Salukis were historically bred in the Fertile Crescent where agriculture is widely believed to have originated. Like Afghan hounds, Salukis tend to have long legs and a thin build. They are known as sight hounds, meaning that they hunt primarily by sight as opposed to by smell or other senses. Today, they are bred with coats in a veritable rainbow of colors ranging from red to tricolor (white, black and tan).
The Greenland sled dog, also sometimes referred to as a sledge dog, is yet another early East Asian breed. The recent DNA analysis conducted by Bogdanowicz and his colleagues "revealed post-divergence gene flow from grey wolves to Greenland sledge dogs," they wrote. This determination reminds that free-breeding dogs can still interbreed with wild canines, such as grey wolves, coyotes and golden jackals. The resulting offspring can be fertile, and conservationists are concerned that we may one day lose the uniqueness of wild canine species due to hybridization.
Wayne and his team found that only two East Asian breeds, the chow chow and Akita, "had higher (genomic) sharing with Chinese wolves" than other breeds. Researchers can therefore see past wolf contributions to the modern dog genome. Other wolf populations noted in the dog DNA studies include those from North America, the Middle East and Europe.
The Samoyed, as a distinctive breed, originated in Siberia, where nomadic reindeer herders bred them as sled dogs and to help with herding. Their historical past is much deeper, however, as these primitive dogs descend from an even earlier, founding population of Russian dogs. According to an American Kennel Club fact sheet, "Of all modern breeds, the Samoyed is most nearly akin to the primitive dog. No admixture of wolf or fox runs in the Samoyed strain."
The genetic analysis of Wayne and his team defined three basic groups of "highly divergent, ancient breeds." They are: *Asian group: dingo, New Guinea singing dog, chow chow, Akita and Chinese Shar Pei *Middle Eastern group: Afghan hound and Saluki *Northern group: Alaskan malamute and Siberian husky All of these dogs were found to be genetically "distinct from modern domestic dogs."
Bogdanowicz and colleagues' study suggests that the Shiba Inu belongs on the ancient dog list. The DNA of this dog shows that it is related to yet another East Asian breed, the Chinese Shar Pei. The American Kennel Club, though, reports that "Shibas are considered the oldest and smallest of Japan's dogs." The AKC only officially recognized this breed in 1992, demonstrating that the actual origin of a breed can happen hundreds of years prior to such designations.
The word "spitz" refers to several different breeds that loosely share common ancestry and traits. They are believed to descend from very ancient dog populations. Bogdanowicz told Discovery News that he and his team "found that spitz-type breeds of European origin -- Keeshond, Elkhound, Finnish Spitz, German spitz and Schipperke -- are genetically distinct from other European dog breeds, suggesting that they may have a distinct origin and possibly may be related to spitz-type breeds from East Asia and the Arctic." A closer look at the friendly dog shown in this photo reveals many wolf-like characteristics, such as a dense and waterproof insulating coat. Dog breeders even categorize spitzes in a unique group that stands apart from the other umbrella terms that they often use to describe dogs: ancient, toy, spaniels, scent hounds, working dogs, mastiff-like breeds, small terriers, retrievers, herding and sight hounds. The spitzes are in a league of their own.