I've got chickens with frostbite on their combs and wattles. It hasn't really even gotten real cold here with the coldest night was in the 20's F and always above freezing during the day. The coop is insulated and they are inside at night. After reading info about vaseline I bought a large jar and put it on every comb and wattle. (They really liked it by the way!) That night the temp got down to 20F and the next day there were more black spots on the comb of my big roo. I read that people don't heat their coops in much colder temps that what I have had. How do you keep them from getting frostbite? For now, I plan to add a heat lamp on the nights where the temp is supposed to drop below freezing.