The major deficit for cats in plant-only diets is the amino acid[sup]1[/sup] taurine, which is only found in meat. We humans are smart enough to manufacture it ourselves from plants if necessary, but cats can’t do that, so they need to eat meat.
[sub]1. Not technically an amino acid because there is a sulfonyl hydroxide where the carboxyl group should be.[/sub]
My late dog Mac was like a goat, he’d eat anything. He once ate the wrapper off of a Gatorade bottle. I kept expecting to find a pile of laminated poop but that never happened.
He never had digestive stress, not that ever showed, so I always figured that dogs have a lot of tolerance for varieties of food (except chocolate of course).
Thanks for the info. I posted about this because if you can convince strict Vegans to feed their cat meat then there must be a good reason. These are smart people, I’m sure they did the research and found the justification they needed.
Right. Even animals that we think of as pure herbivores like deer will occasionally eat animal matter. Deer will eat baby birds, eggs, fish, and carrion. This is probably mainly for minerals rather than nutrition.
Obligatory youtube video of a cow eating a bird:
If the minerals are required and otherwise lacking, I would say deer eat what they eat for nutrition. 
That’s not Kosher!
We then must ask: are you plant matter, or made of meat?
How do you know if the cow is Jewish?
My hounds are omnivorous. Beyond their dog food and other meats I give them, they eat frozen bananas, lettuce, cucumbers, strawberries and other fruits and vegetables that I always check if they’re safe before I give them to them.
My cat is made of pure evil, she keeps thinking she can suck my soul out of my body by biting me I guess … it’s just the one cat of mine that does this regularly, so either she’s the smartest of the bunch or just plain insane.
As the learned post above noted, dogs aren’t natural. Just like humans have extensively changed and varied their appearance, it stands to reason (though no biology or breeding expert) you could selectively breed also for ability to thrive on non-meat. It’s obvious for anyone who has had dogs that the typical modern examples have some appetite for non-meat, though varying by dog (our current dog will eat some vegetable not others, previous dog would not generally eat any vegetable, both enjoyed most fruits and bread, in an otherwise adequately fed state).
Many years ago I found brilliant blue feces in the cat litter. Not the grayish hues that sometimes may be described as ‘blue’ in describing things that are not blue, but bright solid cobalt blue. Was confused. Sometime later while packing to go backpacking found that one of those old crappy blue sleeping pads had been chewed up. Guess they liked the texture.
This thread makes me think of the the newly pragmatic character in Shirley Valentine feeding the dog steak instead of its pretentiously defined vegetarian meal.
Given that dogs evolved for thousand of years to live closely alongside humans, one would think that their diets would have changed to be more consistent with ours. Those that could live best off our scraps were the ones that reproduced the most. That, of course, ignores a certain amount of intentional selective breeding on our part, but that’s probably just a drop in the gene pool bucket if you look at “dogs” in toto.
Trying to decide if a dog is a carnivore based on the foods that it is given by its owners is a fool’s errand. That doesn’t tell you much about a dog’s natural proclivities. However, dogs are certainly known to gnaw on and graze on grass from time to time. That would indicate that they’re not exclusively natural carnivores, but that they do eat plant matter from time to time. As **Chronos **suggests, these categories are not simple and mutually exclusive - there’s a variety of diets in the animal kingdom.
It could still have rice, if they consider rice to not be a grain in the same sense they may see corn.
Or even without rice, grain-free diets do still contain alternate sources of carbohydrates.
That said, then… it does not necessarily follow that the alternate sources of carbohydrates they use would be any more or less natural to the dogs than corn.
It hasn’t been determined why dogs eat grass (wolves do too), but it’s not as a source of calories, since they can’t digest it to any extent. Probably the best guess is that the fiber helps to get rid of intestinal parasites.
As mentioned above, wolves will eat fruit, which they can digest and provides some nutrition. And dogs acquired genes that better enable them to digest starch (and thus live on human foods) early in the domestication process.
Nope, it has no rice.
Merrick is the brand. Beef, lamb, salmon, peas, sweet potatoes, apples, blueberries, etc. No rice.
Expensive, but our dogs do well on it.
I don’t have a dog, but a good friend of mine has a Lab and that dog will eat damn near anything. Chips, peanuts, crackers, cookies, broccoli, whatever you throw at him. I always kid my buddy that he’s starving his dog because the dog is always ready to chow down on whatever he’s offered.
The dogs we’ve raised with retriever blood (full or half golden or lab) have been real goats, too.
Reminds me of an old “Rhymes with Orange” comic by Hillary Price (which I can’t seem to google up for you), about a Labrador Retriever Flow Chart (demonstrating the method a dog uses to determine if something is edible). Basically it boils down to “eat it, and if it stays down, it’s edible”.
In addition to chocolate, try to keep grapes, raisins, onions, and garlic away from your dogs. (And especially don’t let them have raisinettes with garlic salt. 
)