No, it won't hurt them. Before I started using All Flock or Starter/Grower, depending on what my closest feed store had in stock, (and my closest is a 50 mile drive one way!) mine would get into the layer food no matter what I did. That's why I put the whole flock - roos, layers, and chicks of different ages - on one single food, with a separate container of oyster shells for the layers. They take just what they need. Too hard to keep them from each other's food when you have your chicks totally integrated by 4 weeks old like I do.