Two foods can list the same percentage of protein but deliver different amounts of usable amino acids. Animal-source proteins are typically more bioavailable than plant-source proteins — your pet absorbs and utilizes more of the protein content. Mineral bioavailability also varies: chelated forms (zinc proteinate, copper proteinate) are absorbed several times more efficiently than oxide or sulfate forms. Bioavailability isn't on the label but is part of why ingredient quality matters beyond raw percentages.