I have 20 chickens. Now that they are getting older I am free ranging them more and more and in about a month or 2 they will free range 100% of the time only going in the coop to sleep at night. Is there math to find out how much addition feed they will need? They have a good 1.2 -1.8 acres they range on. Right now they free range all weekend and I have been cutting back on the feed and they seem starving all the time. Are they just being lazy?