We start them out as soon as they will start. We start by feeding the dams and the calves get nosey. Couple of days and there coming to the bucket to. Once they get the taste they soon find the creep feeder. Usually start out with a generic 12% feed. It seems to help the body condition of the cows also because the calves are getting full quicker and not draining the cows. Good luck with whatever you decided.