The majority of tissue processed comes from slaughterhouses, but also includes restaurant grease and butcher shop trimmings, expired meat from grocery stores, and the carcasses of euthanized and dead animals from animal shelters, zoos and veterinarians. This material can include the fatty tissue, bones, and offal, as well as entire carcasses of animals condemned at slaughterhouses, and those that have died on farms, in transit, etc. The most common animal sources are beef, pork, sheep, and poultry.