A common question and one posed by the user Victoria on our very own DogChat message board.

User Lara’s Yorkies believes:

I think dogs are oppurtunists, naturally carnivores but will eat anything really

and it would seem there is some general concensus that dogs can actually be vegetarian but they may not always thrive as such.

See the full thread:
http://www.petfriendlyworld.com/chat/controversial/can-dog-go-veggie-diet/0/