I also raise pheasant. I am wondering if you have lighting on for them. Some people put clear heat lamps on. I have read that this promotes cannibalism. I only use red heat lamps and I have hatched and raised about 120 pheasant this past season and have not had this problem. Good Luck!
I feed my guineas game bird food. It is especially made for guineas, peafowl, pheasant and such. They gain well and grow up healthy. I am on my fourth batch of guineas now!
I have lowered ceilings and I store hay up there for most of the winter so it helps with the insulating. I also use lights , I hang one in each coop, it helps alot.
I let my chickens out on a regular basis. They return back to their coop by themselves as the sun goes down. They also go back into their coop to lay their egss, then back into the yard to play some more.