We were going to cull and process our extra roos today, but I got a hold of them (we just got them this past Tuesday from a questionable home), and most of them are pretty thin. I'd like to add some weight so they are worth the work. There's quite a few, so I'd like to add the weight as fast as possible. Besides putting them on broiler feed and corn, is there anything else I can add? I feed raw and often have a good bit of leftover raw chicken fat I can give them.