Are Dogs Carnivores Or Omnivores?
The debate continues as to whether dogs are still carnivores or have evolved into omnivores. We’ve known for years that they’re able to digest carbohydrates. And there’s interesting speculation about when and how that occurred.
Theories are that our prehistoric ancestors took to throwing food out to prehistoric canids that lurked in the shadows beyond the campfire because A: they felt sorry for them, or B: because they didn’t want to be eaten themselves.
For thousands of years man and beast saw a peaceful coexistence gradually evolve into a relationship and thus the dog became domesticated. They became valuable as hunters, herders, haulers, protectors and BFF.
Our forebears loved the little guys and readily shared their food with them…unless there wasn’t enough meat to go around. Sorry, Boomer, here, have a piece of bread.
Over the centuries, apparently, the dogs were able to keep the non-flesh stuff down and, in fact, adapted a gene that enables starch digestion. So in the late 19th century when commercial dog food arrived on the scene, grains were a major component of the kibble.
Let’s fast forward to today. I wondered if by digestion they meant: able to convert food into nutrients that could be absorbed and assimilated by the body, or simply be able to ingest it, have it travel safely through the digestive tract, and excrete it.
Our dogs regularly swallow non-food items and poop them out. Since they pass through the entire digestive tract, but are not absorbed or assimilated, are they still digested?
Most definitions of digestion say “absorbed and assimilated.” The Bing definition also includes “or excreted.”
Take your pick. I find the Bing definition intriguing. That’s because I also wonder why the manufacturers’ feeding instructions vary so much between grain-based and meat-based feeds.
A typical grocery brand that starts with whole corn, contains other forms of corn such as corn meal or corn gluten meal, and uses other grains such as wheat, sorghum, and soy, suggests as much as eight cups a day for a 100 pound dog.
A typical grain-free dog food that contains none of the above suggests up to to five cups a day for that same dog.
Dogs on the grocery brands typically produce large volumes of stool, which are occasionally soft and difficult to pick up, while dogs on grain-free foods typically produce “little cigars” that are easy to pick up.
Flatulence commonly is a major issue with dogs on the grocery brands. They can clear a room quickly, can't they?
If they efficiently absorbed and assimilated the grains, why would they (A): need to eat twice as much as meat-based feeds, (B) produce so much more waste, and (C) be so gassy?
Perhaps a Board Certified Animal Nutritionist will read this and comment below with an easy-to-understand answer.
But that’s not the only reason why I’m personally on the side of “they’re carnivores.” DNA studies prove the dog descended from the timber wolf (or gray wolf, depending upon your source) anywhere between 30,000 and 100,000 years ago (depending upon your source). Domestication began around 15,000 years ago.
Some scientists and lay persons opine that the dog has evolved into an omnivore, others don't. I still have a hard time accepting the omnivore position because their “carnivore’s anatomy and physiology” haven’t evolved.
When you tour the entire alimentary tract of the dog, it sure looks like a carnivore’s alimentary tract. Let’s tour together.
It Sure Looks Like A Carnivore's Digestive Tract
Let’s start with the saliva, that enzyme-rich juice that begins to break down food before it reaches the stomach. There’s a specialized enzyme called amylase, that's entrusted with the job of breaking down carbohydrates into sugars.
Humans are omnivores and our saliva is equipped with it, as is the saliva of herbivores such as horses and cows. Carnivores lack amylase in their saliva, and so does the dog. I think we have to put a check mark in the “carnivore” column.
Now let’s look at the teeth. Omnivores have a variety of teeth. Some are broad and sharp (incisors) for cutting, some are pointy (canines) for tearing, and others are flat and boxy (molars) for crunching and crushing.
Herbivores have incisors and molars, but no canines. The dog has a few incisors in front, but everything from the canines back is narrow and pointy. I think we have to put another check mark in the “carnivore” column.
How about the way we chew? Humans and herbivores chew up and down and side to side, albeit more pronounced in the case of herbivores.
Dogs (and cats, which are obligate carnivores) can chew up and down only. Do you agree on another check mark in the carnivore column?
Let’s compare gastro-intestinal tracts. We have relatively small stomachs and a relatively short intestinal tract because we consume small but frequent meals.
Herbivores have a GI tract that typically is about 10 times their body length because they’re pretty much grazers. Horses have a digestive tract about 100 feet long.
Ruminants (cud chewers such as cows, deer and other hoofed animals) need four-chambered stomachs to break down their food, plus they need to regurgitate and re-chew it (the cud), mixing it with more amylase-rich saliva before sending it back to their stomachs for additional processing.
Then they have this long intestinal tract to facilitate the relatively slow absorption of nutrients from the forage they’ve been eating almost constantly.
Dogs have a relatively large stomach and shorter intestinal tract because they’re adapted for eating larger, less frequent meals.
Also, their digestive juices are highly acidic to enable the stomach to break down meat quickly so that their relatively short intestinal tract can absorb the nutrients before they’ve had a chance to exit the dog.
The dog’s strong digestive juices also kill bacteria that often contaminate raw meat. That’s why foxes and other wild canids can bury (cache) leftover meat, then dig it up and eat it a day or two later.
There are often pet food recalls associated with salmonella contamination, but the threat is more serious to people than the dogs.
A healthy dog won't be affected by the salmonella for the reason stated above.
In fact, though, a healthy adult human probably won't either. Salmonella poisoning in healthy adults usually produces mild symptom that are dismissed as "I must have eaten something that didn't agree with me."
It's a different matter for the very old, very young, or those with compromised immune systems, though.
It’s also why your dog…when he comes home from doggy daycare and you’re upstairs changing clothes and taking care of other business…can eat that raw hamburger that’s been thawing on the kitchen counter all day and not get sick.
One other thing, in the form of a question: if you look in the dog’s small intestine, guess what you’ll find? Answer: amylase.
I wonder how much nutrient from carbs can be absorbed in the short time those carbs are in the intestines? Can I get an Amen for another check mark in the “carnivore” column?
And look at the lifestyles of the various different animals! Ungulates stand around all day alternately chewing vegetation and cud, eventually moseying on over to the next patch of forage.
The only exercise they get is trying to evade predation (skills that remain works-in-progress) by those pointy-toothed, amylase-challenged carnivores with the relatively large stomachs but otherwise relatively short digestive tracts.
The carnivores, on the other hand, have to hunt for and bring down prey usually several times their own weight, patrol and defend a territory, compete for and defend a mate, and maintain discipline and decorum within the pack.
I’m not a nutritionist, but I’d bet that would be tough to do on a diet rich in salad. Allow me that one for the “carnivore” column?
My scorecard has it 5 to 0 in favor of “they’re carnivores.” How about your scorecard?
Here’s a theoretical question: If you dropped a dog off a hundred miles into the deep woods, do you think he’d browse for forage or hunt for game? I believe he’d hunt and, if unsuccessful, may resort to eating vegetation.
But I wonder how well he’d do and how long he’d survive on such a diet. Escaped dogs that evade capture for weeks often are trapped or otherwise apprehended in a somewhat emaciated condition.
Could they survive for months or years if vegetation were a significant part of their diet?
The debate is an interesting one, isn't it? But in the scheme of things, pretty insignificant. No matter which side of the debate we're on, we can all celebrate the domestication of the dog, reflect upon his importance in our daily lives, and his status as our BFF.
Which Side of the Debate Do You Come Down On?
Do You Believe That Dogs Are Carnivores or Omnivors?
© 2013 Bob Bamberg