I wouldn't leave bowls of raw meat out for them or give them anything that has sat out but as long as they're eating it as you cut it off the carcass or shortly thereafter (or if you keep it refrigerated and take it out to them and they eat it up right away) there's no problem. Chickens will catch and eat their own raw meat given the chance. They love mice, frogs, chipmunks, etc. As long as it's fresh, not rancid they'll be just fine. You could even freeze the parts you don't use from later kills and thaw it out occasionally as a treat/dietary supplement.