On the cornbread, I put a bunch of corn meal right out of the bag on some fire ant hills a while back, to see if it would kill the fire ants as I've read. The chickens scarfed up the meal in no time. If they can eat it raw, surely they can eat it cooked in bread.
I don't give them sweets, and limit anything very salty or fatty, but other than that, they get most anything around. I've read that potato peels are toxic to them, but I've also read that they won't eat them, as well as that they eat them without a problem. I don't worry about it. I figure there are a lot more poisonous things where they free range than what comes out of my kitchen.
If I don't eat it raw, though, I don't feed it raw. Sometimes it won't matter, as with oatmeal, but sometimes it will, as with dried peas and beans.