You transition from starter feed to grower feed. Grower is usually around 18% protein with the appropriate amount of calcium for that age level. As you go from starter to grower to layer rations the calcium level changes appropriately. If your wanting a specific amount you will have to read the bag.
We have ducks, so they eat either 22% to 28% the chickens love it.. :yiipchick
Our flock seems fine. Never had any issues..