I have (13) 9 week of chicks and (3) 8-12 month old hens. How much feed should I be giving them each day. Currently I use a big plastic coffee can, usually filled to the 3/4 or full mark each morning. I can go out about 3 1/2 hours later and it is all gone. They come running to the fence when I come out and they act like they are starving. I am using a 20% grower feed. How much should I give them each day??