This time of the year, the only thing I can grow for my chickens is turnip greens. And even that has to be grown under row cover. I did overseed a portion of the lawn with rye seed, to give them a little more winter greens.
Most of the year, I grow organic food for us HUMANS, but the chickens get benefit from that too. I give them the outer leaves of the cabbages, broccoli, and lettuce plants. They get to eat less than perfect watermelon, or even that last slice of perfect melon after my wife and I have had our fill. They get plenty of less than perfect tomatoes (misshappen fruit, fruit that has a slight blemish, etc). They THINK that the raspberry plants are for them, and can't understand why some of the berries mature higher than chicken height. They would get into my strawberries, if I didn't keep them under row cover.
I'm going to grow corn especially for them next summer -- some non-GMO, heirloom variety. Maybe hopi blue or bloody butcher. I'd never be able to grow a years supply of corn for them, but maybe I can grow some. I was talking to a farmer just today who not only grinds up his whole kernels, but grinds up the cob too, and gives it all to his chickens. If I can find a grinder for my cobs -- or perhaps use his -- then I think I'll grind up the cobs for my chickens too.