AS a kid on the dairy farm, my job was to feed the chickens. They got whole wheat, oats, corn, and a mash that was ground on the farm as a dairy ration: corn, oats, malt, toasted soybeans and a bag of minerals. Plus they were our garbage disposal for the farm garden surplus.
I assume my parents had a clue about chicken nutrition because they had a commercial laying flock in the '40s. The chickens were healthy, laid plenty of eggs and lasted quite a few years. They were not free ranged, but had a large oldfashioned chicken house with plenty of room.