I have 18-12wk old RIR & Australorp and we live in a pretty cold part of CO. They are going through 50lb bag of feed in about 10-12 days- with little extra food. They don't free range and our night time lows are below 0 now. I assume that chickens will eat when they are hunger and stop when they are full...but I may be wrong. Are they eating the feed to quickly or just growing. I think the latter.