Where I live, people often call cracked corn "chicken feed."  I can drive down my road about 1 mile and buy this "chicken feed" much cheaper than layer or starter/grower from the feed store.  Traditionally, they feed cracked corn and table scraps, and let the chickens free range.  And I do mean free range.  In the road, in the parking lot at the jiffy store, in the neighbor's cow pasture, wherever.  So the chickens find plenty of bugs, snakes, frogs, mice, etc.  These people also put hens in the stew pot when they stop laying, so the chickens don't live more than 2 or 3 years.  I never heard of grit til I joined BYC, and at the feed store, when I asked about it, they thought I was talking about Southern grits, as served for breakfast around here.  Oyster shell?  We won't go there.  But then, our soil has lots of sand and limestone, so there's the grit and calcium.
These "old-fashioned" ways, like mixing scratch or cracked corn with feed, are not necessarily the healthiest or most efficient way to raise chickens, but they worked for generations, and I do respect the experience and opinions of the oldsters!  They had few sources of info besides word of mouth.  And we are fortunate to have BYC, because even now, available info and research are limited.