Ask most people, including some veterinarians, whether dogs are carnivores or omnivores, and you’ll be told dogs are omnivores, designed to survive on a combination of plant and animal matter. Yet scientific discoveries in the past twenty (20) years prove those people wrong. Particularly, the genetic research of Dr. Robert K. Wayne and the observational research of Dr. L. David Mech indicate that dogs are carnivores, still nearly genetically identical to the gray wolf, and like the gray wolf, they thrive on a diet of meat, bones, and organs.
In the early 1990s, Dr. Robert K. Wayne and fellow geneticists studied the DNA of wolves, dogs, coyotes, foxes, and other members of the genetic “dog family,” called Canidae. At the time, the dog’s origins were not definitively known. Were they their own species? Dogs themselves show significant physical diversity – was it possible they came from more than one source? Wayne’s research definitively proved otherwise: ”Dogs are gray wolves, despite their diversity in size and proportion; the wide variation in their adult morphology probably results from simple changes in developmental rate and timing.” (Wayne, Molecular Evolution of the Dog Family, 1993)
That’s right: dogs didn’t just evolve from gray wolves; dogs are gray wolves, “differing from [them] by at most 0.2% of mtDNA sequence.” (Wayne, 1993) Their genetic similarities are what enable dogs and wolves to interbreed even to this day. After all, no more than 15,000 years have passed since dogs were domesticated. (Wayne, 1993) In the evolutionary scheme of things, that’s barely the blink of an eye.
Since dogs are nearly genetically identical to gray wolves, can interbreed with wolves, and in fact really are still wolves, it should be no surprise that their digestive systems are identical. From the smallest Chihuahua to the largest Irish Wolfhound, to the wild gray wolf, some things never change: things like teeth, jaws, and intestines, to name a few.
So let’s travel down the dog’s digestive system, explore their basic anatomy, and discover what exactly makes them carnivores.
The Teeth. The first tool a dog uses in digestion is its teeth. If you open your dog’s mouth, you’ll see sharp little teeth from front to back. These teeth are known as incisors (in the front), canines (the longest of the teeth), and premolars (in the rear). Dogs’ teeth are designed to kill prey (with the canines), shred meat (with the incisors), and crush bones (with the premolars). Notably missing from a dog’s mouth are flat molars in the rear. Herbivores (like cows) and omnivores (like humans) have molars because they are needed to grind fruits, vegetables, and grains to begin the process of breaking down the cellulose in the carbohydrates – a necessary step in carbohydrate digestion.
But here’s what you can’t see just by opening your dog’s mouth:
The Saliva. Herbivore/omnivore saliva contains enzymes that, in conjunction with those grinding molars, break down the cellulose, making the carbohydrates we eat digestible. Carnivore saliva acts as nothing more than a lubricant, enabling a carnivore to swallow prey as quickly as possible. Dogs have lubricating saliva, lacking any enzymes for cellulose digestion.
The Jaw. Herbivore/omnivore jaws move up-and-down, and also side-to-side, allowing for food to be well chewed and ground with the molars, again assisting in breaking down cellulose. Carnivore jaws cannot move side-to-side. They can only move up-and-down, like scissors, which does not permit “chewing,” as you might conceive of it. As with the saliva, the carnivore is simply not designed to slowly eat its food, chewing diligently like a herbivorous cow. It’s expected to use its scissor-like jaws, in conjunction with its deadly canines, to take down a prey animal. Then, it uses its incisors and canines to shred the meat from that animal and consume as much as possible as quickly as possible. The scissor-like motion of a dog’s jaw does not enable grinding, as would be necessary to digest plant matter.
The Stomach Walls. Herbivores/omnivores generally eat many small meals each day. They graze and, accordingly, their stomachs can only healthfully fluctuate so much in size. Carnivore stomachs, including dogs’ stomachs, stretch to many times their normal size, enabling carnivores to gorge (eat as much of their prey as possible immediately following the kill), and then rest.
The Stomach Acid. Herbivore/omnivore stomach acid is designed to digest plant matter and well chewed food. Compared to carnivorous stomach acid, it’s downright weak. A dog’s stomach fluid is significantly more acidic, which enables dogs, as carnivores, to break down bones and other food that’s been crushed and swallowed (but not chewed).
The Intestines. Herbivore/omnivore intestines are rather proportionately long, affording the ground and semi-digested carbohydrates time to ferment in the gut, making the nutrients therein available to the eater. Carnivore intestines are short, so that the bacteria naturally occurring in meat pass through the carnivore quickly, leaving them no time to “set up shop” in the intestine and cause digestive upset (like they would in a human). Because dogs’ (and other carnivores’) intestines are short, even partially ground, pureed, and/or steamed vegetables do not have sufficient time to ferment in the gut. Full digestion is impossible.
But carbohydrates are cheap. And carbohydrates are a natural part of human garbage. We eat them, so we throw them away. Dogs, being opportunistic, will eat whatever they can (including socks, goose and cat poop, and the occasional remote control – a sharp reminder that just because a dog can eat something, and wants to eat something, doesn’t necessarily mean the dog should eat that thing).
When dogs were eating our table scraps, as a byproduct of domestication, their diets changed to include whatever fruits, vegetables, or grains would have otherwise gone to waste. However, since dogs have only been domesticated for about 15,000 years, they haven’t actually evolved to a point where those items are actually beneficial for the dog. Still, it understandably became generally accepted that dogs could and would eat these items. Additionally, carbohydrates are a necessary ingredient in any kibble. They are the binding agents that hold the little clumps together. Be they rice or potatoes, there will be some kind of starch in kibble.
But, as with socks, remote controls, and even antifreeze, just because dogs can and will eat carbohydrates doesn’t mean they should. As we’ve discussed, “[d]ogs do not normally produce the necessary enzymes in their saliva (amylase, for example) to start the break-down process of carbohydrates and starches; amylase in saliva is something omnivorous and herbivorous animals possess, but not carnivorous animals [including dogs]. This places the burden entirely on the pancreas, forcing it to produce large amounts of amylase to deal with the starch, cellulose, and carbohydrates in plant matter. The carnivore’s pancreas does not secrete cellulase to split the cellulose into glucose molecules, nor have dogs become efficient at digesting and assimilating and utilizing plant material as a source of high quality protein. Herbivores do those sorts of things.” (Case, Carey and Hirakawa, Canine and Feline Nutrition, 1995)
For many years, it was believed that wolves ate partially digested plant matter regularly, by digesting the stomach contents of their prey. So, even raw feeders believed it was best to feed carbohydrates to their dogs, because they believed it was natural and necessary for dogs (like wolves) to consume such matter. Knowing a dog’s mouth and stomach acid were incapable of adequately digesting plant matter, BARF feeders would steam and/or puree this plant matter, hoping that doing so would mimic partial digestion and enable their dogs to derive nutrition from the plant matter.
As discussed above, the canine anatomy is not capable of efficiently deriving nutrition from even partially digested plant matter, due to their short, small intestines.
More significantly, the research of Dr. L. David Mech, Senior Scientist with the Biological Resources Division, U.S. Geological Survey, and Adjunct Professor in the Department of Fisheries, Wildlife and Conservation Biology, and Ecology, Evolution and Behavior at the University of Minnesota, has dispelled the popular myth that wolves eat the stomach contents of their prey. In over fifty (50) years of observing and researching wolves, Mech determined that “[w]olves usually tear into the body cavity of large prey and consume the larger internal organs, such as lungs, heart, and liver. The large rumen…is usually punctured during removal and its contents spilled. The vegetation in the intestinal tract is of no interest to the wolves, but the stomach lining and intestinal wall are consumed, and their contents further strewn about the kill site.” (Mech, et al., Wolves: Behavior, Ecology, and Conservation, 2003) The stomach lining and intestinal walls are muscle matter, not plant matter, and are therefore a desired food for the wolves. Their contents are left behind, uneaten.
Dogs and wolves are not designed to eat carbohydrates. Every part of their digestive tract dictates that they are carnivores, designed to safely digest prey animals. Knowing they’re not designed to eat plant matter, why feed it?
Would you ride a mountain bike in the Tour de France?
Would you use a samurai sword to whittle a delicate statuette?
Would you take a Lamborghini off-roading?
Perhaps, in each of the above examples, you could. But knowing that these tools were designed for a different purpose, knowing there were other tools better suited to your uses, why would you? Just as you could feed your dog carbohydrates… but why would you, knowing that ‘s not what they were designed to eat?
The dog’s teeth, jaws, saliva, stomach, digestive juices, and intestines all dictate that the dog is a carnivore designed to eat the bones, the organs, the meat, the fat, the connective tissues, and all the other parts of prey animals. This is why the Whole Prey Model raw diet – in which the dog eats as many diverse parts of prey animals but no fruits, vegetables, starches, etc. – is often referred to as a “biologically and anatomically appropriate diet.”
By eating foods that its body is designed to digest, the dog can obtain the most nutritional benefit with the least amount of taxation. The food is highly “bio-available” to the dog. Less stress on the digestive system, particularly the pancreas and kidneys, and more bio-available nutrition, leads to better immune system functionality and overall health.
A longer, happier, and healthier life for your pet – what more could any “paw”rent ask for?