By-Product

By-product is an AAFCO-defined term referring to animal parts other than muscle meat. By-products include organs (liver, heart, kidney), frames, feet, and necks. The AAFCO definition specifically EXCLUDES feathers, hair, hooves, horns, and intestinal contents. By-products are nutrient-dense (organ meat is some of the most nutrient-rich food on earth) and not harmful, despite the marketing fear. Premium feeding-trial-validated brands like Hill's and Purina Pro Plan use by-product meal because it works. Budget brands also use it because it is cheap. The quality variation comes from the source, not from the by-product designation itself.