Do you have any Hispanic or Asian stores around you? Maybe even a little distance away? I get all my dog food from Hispanic grocery stores (Brain, Kidney, liver, heart, dirt cheap chicken etc.) If you can find one of those, even if it's a half an hour drive or so it's really really worth it.
I follow their deals and stock up when they have them and believe me, I've gotten some amazing deals on things there. .29 Chicken backs, .49 Chicken saddle legs etct.