I cut a deal with a local grocery store to take some of their day old produce and other expired stuff to save them dumpster space and to put some of it to good use vs just tossing it away... They won't give me any meat products but I get offered more fruits, vegetables, dairy, bread and some expired canned or other packaged items then I can use each day... I could literally fill a pickup truck full nearly every night from this single store, but don't take nearly that much, only what my birds will eat that day, unless it's something that will last a few days... And it's a varied diet as they toss different stuff away every day...
My birds were consuming about 150 pounds of feed a week, now they consume about 50 pounds of feed, so it's a huge savings... They always have access to their commercial feed if they choose, and I have not seen a drop in egg production since I started doing this...