I grew up on a chicken and sheep farm. Between letting the chickens roam the vegetable part of the farm area and eat bugs (bonus: we didn't need pesticides) and feeding them our organic food waste, we basically spent nothing on chicken feed. I found out about chickens being zealous cannibals accidentally when I was a kid taking the trash out to feed them. We'd had fried chicken for dinner, and I wasn't thinking about it and just threw all the bones into the feeder like I always did with the food trash. They went berserk over those chicken bones. They absolutely loved them. It was a shark-style feeding frenzy. I was weirded out by that for a while.
It was a pretty small operation though. OP's idea for chickens might make sense in a factory farm situation where there's no space to let them roam for bugs. And maybe the logistics of getting them fresh trash don't make a ton of sense.