nina1marc2, hmmm, well at 16 weeks your chickens are actually ready to be marketed for meat if you choose. They should have been off starter food a long time ago. On the back of most starter grow packages, you will find an age chart which helps dictate when to change to another reccomended feed product. Oyster shell and grit supplements are added in much the same way according to age and the cycle of laying. You may not need oyster shells once your birds reach full adult age and are on a proper feed that contains the ingredients needed for healthy egg shells. Same with grit, if they are free ranging, they manage to ingest some of the soil particles which help them digest their food better. IMO, its good to add oyster shells about a month before they reach the age to begin laying. Hope that helps.
