When it comes to a flock with younger and old feathered friends, you will want to choose your feed based on the youngest members of your flock. This likely means feeding Little Pecks to your whole flock as your little ones grow big and strong since feeding chicks under 20 weeks of age too much calcium can be detrimental to their health. However, you will want to supplement your older layer hens with free-choice oyster shell for supplemental calcium.