Back before people had nutritional science figured out, the key to success was to let livestock (and people) pick and choose from a wide variety of foodstuffs. Confined animals (and people) fared poorly. Sailors suffered from scurvy at sea, and people in institutions suffered from pellagra, but the same people never had these problems when given a little freedom, even though they knew nothing about nutrition. They just listened to their cravings.
Nutritional science means that you can get away with giving livestock (and people) a balanced diet without any food choices, but that doesn’t mean it’s always the right thing to do.
The most time-honored method of feeding chickens a balanced diet is cafeteria-style feeding. The original method included “chicken mash” (a mix of grains, steamed beef scrap, and other ingredients) in one trough, grain in another trough, oyster shell in a third, and pasture or hand-fed green feed on the side. The chickens were left to figure out how much of each ingredient to eat. This works quite well.
You can take advantage of the fact that the chickens won’t starve in the midst of plenty in the following way: always provide a feeder full of a quality, balanced chicken feed, and offer anything else you’ve got on the side. If the chickens like the side offering, great. If they don’t, they’ll just ignore it and eat the balanced ration. This method leverages the fact that the chickens are better judges of chicken feed than we are. Practically the only way to poison or starve your chickens is to force them to eat an inappropriate feed by offering them nothing else. If you give them at least one decent alternative, they’ll be okay.
I feed a high-protein layer ration in one feeder and whatever grain is cheapest in another. I feed a second grain as scratch feed, scattering it in the grass. Hand-feeding keeps the hens friendly. Oyster shell goes into yet another feeder. Grain is usually cheaper than a balanced ration, so you can save a little money by feeding it on the side.
For some reason, lots of people don’t like the idea of separate feeders, and want to mix everything up. Don’t do that. It wastes your time and annoys the chickens. Other people prefer superstition to science, and go out of their way to find a hippie-dippy feed formula, or feed nothing but grain. Don’t do that, either. When humans adopt ludicrous diets, they minimize the damage they do to themselves through the miracle of cheating. Your livestock have no such option, so their diets need to live up to a higher standard than ours.
So now you know the secret: a feeder full of high-quality chicken feed gives you the freedom to try anything else on the side and see what happens.