They are carnivores. However, they get their veggies through the prey. Example: give a dog some special expensive junk that has plants and fillers, he will not be as healthy as the dog you give raw meat to. The teeth of the dog who gets raw meat (including bones) will be stronger, as they absorb calcium from the bones and obviously all that they need for vitamins and protein from the meat - as long as you get the right meat of course. Dogs, don't eat grass for a main staple. They may eat grass if bored, or not feeling well - or as an aid in their digestive track.
Don't ask why I know this :p
My dad's dog won't touch greens
But veggies won't kill dogs. Well...some won't...