Dogs are carnivores. Any ingredients that are not meat, fat, organs, or bone are there for some reason other than nutrition. My dogs have been fed their ancestral diet, the "prey model raw" or "raw meaty bones" diet, since they were pups.

Many people and entities will try to convince you that dogs are omnivores. They are not, regardless of the taurine issue that people try to use as evidence. The physiological characteristics of the entire digestive tract of a domestic dog, regardless of size, is identical to a wolf.

Naturally the pet food manufacturers have been the greatest and most "vocal" proponents of the whole "dogs are omnivores" theory, which most present as fact. That gives them justification for including inappropriate and inexpensive ingredients in dog food that act as binders and/or fillers. Only one pet food company that I know of, Champion in Canada, which produces many brands including Orijen, had the balls to publish a factual white paper on dog biology in relation to nutrition. They even admit that anything that isn't an animal product in dog food is a filler and binder, some of which is necessary to extrude the food into kibble. It's a good read, highly recommended.

https://www.orijen.ca/wp-content/themes/orijen/res/resources/ORIJEN_White_Paper.pdf

They have many other interesting documents here as well;

https://www.orijen.ca/us/library/

Good forum for raw feeding: http://dogfoodchat.com/forum/raw-feeding/

One more good resource, old but still valid: http://rawfed.com/myths/