Most if not all canine nutritionists agree the dog is, to a very large extent, a meat, organ and bone eater, an animal very poorly equipped to handle and process plant material. He is a scavenging predator. A whole-animal eater. A carcass-finding machine. A long-distance-hunting machine. Just look at those teeth! Ever see an omnivore with teeth like that? They’re not for attacking a wheat field. They have no grinding teeth and have no sideways movement of the jaw, all required for tough plant forage. They have forward facing eyes for hunting and no amylase in their saliva for breaking down plant carbs. And these are just the outside traits!
Inside they’re all about meat digestion, with a gut like battery acid and a short, rapid digestive system, no caecum and have bacterial flora ill-equipped to break down plant fibre. Everyone agrees, canine nutritionists and even the dry pet food companies, that dogs have zero metabolic need of plant carbohydrates (Corbett et al. 2001, Sillero-Zubirii et al. 2004, NRC 2006, AAFCO 2008), the very definition of a carnivore. They can actually make their own in a process called glycogenesis, a trick exclusive to meat-eaters. There isn’t a single canine biologist that disagrees this is every bit the meat eater.
What Do Dogs Eat Part IV “The Digestive Machinery of the Dog”. 8mins (If you know he’s already that he’s largely a meat eater, skip it!).
How much plant material do they consume?
There is great debate over how much plant material dogs would normally select when left to their own devices. While some canine nutrition legends like Steve Brown are confident that the dog selected a lot of plant items back in the day, most of us are unsure just how much. Muddying the water at this point are the current diet studies of domestic dogs which have failed to distinguish between village or free-to-roam and feral dogs. We know village dogs, raised by humans in poorer countries where dog roaming laws are lax, usually on diets containing cheap vegetable material, may select plant items from a village dump when allowed to free roam during the day. Feral dogs largely do not do this. It happens that is the former we usually study as they are so successful. Results from these diet studies can indicate that dogs can eat a lot of vegetable matter (up to 40%) but this says little of what the dog selects normally when left to his own devices. Unfortunately, these studies of feral dogs are all too rare though they do indicate a much smaller vegetable component to the diet, less than 10% for the most part.
The feral / free-roaming dog issue is best highlighted with a study by Kuo in 1967. He divided 100 Chow Chow pups into three groups (what a job, imagine that!), to one group he fed all plant material, to the second all meat material, to the third a mix of the two. What he found down the line was that the pups fed only vegetable matter would only eat vegetables later in life. Those fed meat would only eat meat and those fed a mix would eat anything. What Kuo proved quite simply was that dogs can be targetted to certain foods, a process that begins in the womb (you can actually spray the scent of apple in the air of a pregnant bitch and pups will fight over apple-tainted nipples). Hence you can feed Mum dry food and the pups will eat it later in life but if you offer dry food to a fresh fed dog they’re highly unlikely to eat much of it with great gusto.
For me, the most convincing argument for dogs eating a LOT of meat when left to their own devices, is the information coming to us on the domestic dog / dingo hybrid. If we forget wolves for the moment, something the dog hasn’t been for 100,000 years, the dingo is more suitable animal to look at to help us understand what’s going on diet with the dog, the dingo being a domestic dog only 2-4,000 years ago. In a huge study of nearly 10,000 domestic wild domestic dog-dingo hybrids (they were culling the population to save pure dingos from extinction), they found approximately 97% animal (carcass, rabbits, birds, insects, frogs etc) with the 3% coming from bird stomachs “where the prey could not be shaken free”, in their stomachs (Fleming et al. 2001). So, very carnivorous it seems.
Every independent biology book on the matter agrees. Dogs love it and thrive on it, and the fresher the better.
Unfortunately, meat is expensive, which is not ideal when the aim is to make outrageous profit selling cheap, cereal-based cat and dog food. So over the last few decades dry food companies, via our veterinary universities thanks to extremely generous financial donations, have started re-teaching us that the dog not only is not only an omnivore (a meat and plant eater) but that he actually does better when fed largely plant material, a diet that is ultra low in meat protein and ultra high in cereal/carbohydrates. It’s just a lucky coincidence that this also happens to be much cheaper to produce!
That’s not to say you can’t feed some plant material such as vegetables and fruit to your dog for great benefit, you can when done correctly, and I recommend it, it’s just not a large component of the diet.
Kuo, Z. Y. (1967). The dynamics of behaviour development: An epigenetic view. New York: Random House.