We feed all our chickens a mix of feed. We feed them pullet layer feed from the feed store. Then mix in millet, cracked corn and wheat in with the grain and feed that to them. My girls recently started laying so i gave them a little container of oyster shells and they gobbled them up right away, the roosters included! I wanted to make sure there eggs shells were hard enough, but today I ate my first eggs from the new layers and the shells were SO HARD. So i think they must be getting plenty of calcium from their feed. For some strange reason i had it in my head that sunflower seeds were bad, but now that i know differently I am going to include it in the mix!!!