For me it's a no. I don't stop him from picking at grass or eating a bit of spilled rabbit pellets mainly alfalfa. From what I've seen of my dog if he eats fruits/vegetables he tends to poop them out undigested (you would not believe what he's pooped out) so essentially there is no nutrient value in it for him. He does however eat pre-digested from the intestines and stomach of prey animals like rabbit and chicken.
There is nutrient value in fruits and vegetables. However a dogs digestic system can not break through the cell membrane off the plantcells. Thats why they would eat the inside off the stomache aswell, since then they cam get that value and the animal there eating from already broke through thay mambrane. And because.odd this reason I putt all the vegetables through the juicing machine, so this will brake that membrane. (or cook but do so lightly..)
When I roast a chicken or other meat I put carrots and potatoes on the bottom, meat on top. The vegetables are then cooked in the meat juice. I'll give a few pieces to the dogs. They think it is a special treat. I used to feed quite a bit of vegetables this way, then the whole vegetable carbohydrate thing was disputed, so now it's only occassionally.
One of my vets, who is young, probably 30, feeds raw and is a vet chiropractor. Unusual, but even she insists that dogs need carbohydrates because they have evolved so far from the wolf. Poppycock I say. But I just nod. Dogs have been eating kibble for about 60 years, and not all of them have been eating it. That's not long enough for their digestive process to change much. They do not need carbohydrates, that's just the dog food companies line of bs.
Green tripe (green because the animal has been on pasture) isn't just grass that is broken down. It is full of microbes and probiotics. It is a wonderful food and something a carnivore would eat. That is, the stomach lining, not the partially digested grass, vegetables, or fruit. In the wild, canids eat over ripe fruit and not much of it. Overripe fruit is fermenting and the cell structure is breaking down, making the vitamins available.
Actually, dogs have been living with us for 40 000 years or more, according to recent descoveries. They are scavengers, and evolved from early grey wolves which were way more inclined to scavenge than wolves are now. Dogs, having lived with humans, would get whatever humans threw for them, as well as what they could find for themselves. their digestive system has not evolved from being a carnivores, however they have evolved enough to not need Taurine in their diets, the way thet true carnivores (like cats) do. They have changed enough to be able to survive on a vegitarian diet (though it's definately NOT what's best for them), and though they they certainly don't NEED them, veggies, fruit and herbs do have vitamins and minerals that are definately benificial, and they can use and absorb these if they're cooked or pureed (in the case of veggies, fruit doesn't need it). How many poor farmers and peasants in history would share much of the meat they could barely afford, what would dogs have ate then? They were certainly kept by these people for their usefulness, but would have eaten the cerials, potatoes and other cheaper veggies and grains that farmers would have fed their families on, with the odd rodent or small animal they managed to catch or scavenge for themselves. Dogs would not have survived if they didn't adapt to being able to eat, absorb and thrive of diets consisteing of mainly veggies, starches and grains. So although they do not specifically NEED them, it's truly benificial for them to get them.