My mom has a friend who lives on a farm and last time we went I was checking out the chickens/poultry and all the adults got an amazingly horrible diet of straight corn. The chickens, ducks, and geese were all healthy. I do not suggest or support it at all but it can work. It is not ideal and they would do better with real chicken feed but even without it they were okay. The key to them being able to live off of that diet is a very diverse diet from free ranging. they have woods on their property and all their nutrition came from what they found in those woods. Even then I personally feel like their property is just in a very ideal area and a similar type of keeping wouldn’t work most of the time even on similar properties somewhere else
All of this is to say that you should add as much diversity to their diet as you can and hope that it is enough. Along with the food scraps collect weeds, grass, bugs, extra eggs, anything you can find. You can even feed them dead squirrels, chipmunks, mice, voles, raccoons, groundhogs, or anything similar as long as it is freshly killed. Nothing you feed with compare to commercial diets but adding diversity will get you a few steps closer
All of this is to say that you should add as much diversity to their diet as you can and hope that it is enough. Along with the food scraps collect weeds, grass, bugs, extra eggs, anything you can find. You can even feed them dead squirrels, chipmunks, mice, voles, raccoons, groundhogs, or anything similar as long as it is freshly killed. Nothing you feed with compare to commercial diets but adding diversity will get you a few steps closer