Meat by-products are the non-rendered, clean parts, other than meat, derived from slaughtered mammals. It includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth and hoofs. Use of this ingredient from mammalian origins is restricted to non-ruminant (cud chewing) feeds. (AAFCO, 2003) Meat by-products are not meat. They can include almost any part of the animal other than meat. Because any mammal can be used, cheaper meats like horse, pig, or goat are often included.