Beyond the Bowl: Understanding Amino Acid Requirements and Digestibility to Improve Protein Quality Metrics for Dog and Cat Foods

The determination of amino acidAmino acid (AA) requirementsRequirement for mammalsMammal has traditionally been done through nitrogenNitrogen (N) balance studies, but this techniqueTechnique underestimates AA requirementsRequirement in adult animalsAnimal. There has been a shift toward researchers using the indicator amino acid oxidation (IAAO) techniqueTechnique for the determination of AA requirementsRequirement in humans, and recently in dogsDog. However, the determination of AA requirementsRequirement specific to adult dogsDog and catsCat at maintenanceMaintenance is lacking and the current requirementsRequirement outlined by the National Research Council are based on a dearth of data and are likely underreporting the requirementsRequirement of indispensable AA (IAA) for the population. To ensure the physiological requirementsRequirement of our catsCat and dogsDog are met, we need methods to accurately and precisely measure digestibilityDigestibility. In vivo methods, such as ileal cannulation, are most commonly used, however, due to ethical considerations, we are moving away from animalAnimal models and toward in vitro methods. Harmonized static digestionDigestion models have the potential to replace in vivo methods but work needs to be done to have these methods more accurately represent the gastrointestinalGastrointestinal tract (GIT) of catsCat and dogsDog. The Digestible IAA Score (DIAAS) is one metric that can help define proteinProtein qualityQuality for individual ingredientsIngredient or mixed dietsDiet that uses AA SID estimates and ideally those can be replaced with in vitro AA digestibilityDigestibility estimates. Finally, we need accurate and reliable laboratory AA analysesAnalysis to measure the AA present in complete dietsDiet, especially those used to quantify methionineMethionine (Met) and cysteineCysteine (Cys), both often limiting AAs in catCat and dogDog dietsDiet. Together, this will guide accurate feed formulation for our companionCompanion animalsAnimal to satisfy requirementsRequirement while avoiding over-supplying proteinProtein, which inevitably contributes to excessExcess N excretionExcretion, affecting both the environment and feed sustainability.