One year, I planted oat hay, and the down side of that hay was every bale had a mouse nest under it. When it came time to feed the cows, I'd load the hay into my truck. Every bale I picked up had a dog, a cat, and half dozen chickens right there waiting. When I'd pick up the bale, mice would be running everywhere, and dog, cat and chickens would a big mixed up scramble, going as fast as they could, chasing down mice in every direction. The chickens would peck the mouse and kill it, then choke down the entire mouse, head first.
I throw my girls a fresh mouse everytime I catch one. Sometimes they ignore it but most times they fight over it. I think chickens are jealous of one another. One will have no interest, until another looks at the morsel, then they fight over it.
I've also thrown a skinned raccoon into the coop. About a week later it's a skeleton. Good protein for them.
I let mine eat their eggs now, I just bought them a new chicken house and can't let them out without me being right there (and preferably armed) as EVERYTHING likes chicken. Have seen the following try to get them: raccoons, bald eagle, bobcat, mountain lion (a stupid one), and funnies of all was the red tailed hawk that crashed into the side of my house while going after the girls. It wasn't hurt, but got up in a tree and cursed me out real good after that!