My dogs have a diet that is high in protein, and low in carbohydrates - like nature intended. Talk to your local butcher, abbotoir, or chicken processor. Many of the leftovers that these guys consider waste, us BARF people consider fantastic for our dogs. Things like chicken carcasses, chicken necks, chicken feet, and chicken heads are considered rubbish, and are sold for next to nothing. You should be able to get these fairly easily.
Some people also have access to ostrich carcasses, and deers.
You also should be able to get overripe fruit and vegetables very cheap. One great suggestion is going to those places that juice fresh fruit and vegetables for juice, and ask for their leftover pulp. They will probably be more than happy to give it to you. This is the best thing you can do for your bitch. I have actually changed the diet of a bitch I obtained, who was pregnant, to BARF when she was pregnant.