Well not quite anything, but a chicken is a bird and birds eat a wide variety of foods. In nature birds eat everything from fish and other birds, to insect and even mammals. chicken feed is much simpler, but chickens can digest all sorts of treats.
Some birds can use a specialized body part that is known as the gullet. This is an area in above the stomach that holds bits of stone for grinding harder foods into smaller pieces. This allows for the birds to digest almost any kind of food imaginable.
