A Comparative Analysis of Creatine, Creatinine, Amino Acid Concentrations and Indispensable Amino Acid Scores of Grain‐Free and Grain‐Inclusive Commercial Extruded Adult Cat Foods

Despite its role in energy and amino acid (AA) metabolism, no work has investigated creatine (Cr) content in commercial cat food. This study evaluated the Cr, creatinine (CrN), crude protein (CP) and AA concentrations of 30 commercial extruded cat diets. Further, the AA and CP concentrations were used to determine the indispensable amino acid scores (AAS) of the same diets. Diets were classified as grain-free (GF; n = 15) or grain-based (GB; n = 15), then analysed for Cr, CrN, and AA using high-performance liquid chromatography and CP using a nitrogen analyser. Dietary AA and CP concentrations were used to calculate the AAS of each diet, using the recommended allowance for AA requirements from the National Research Council (NRC 2006) and recommendations from the Association of American Feed Control Officials (AAFCO 2023) as reference patterns. Differences in Cr and CrN contents were analysed using PROC GLIMMIX in SAS. The GF diet category exhibited greater (p < 0.05) concentrations of Cr and CrN compared to GB. The most prevalent limiting AA were aromatic AA (AAA) (59%), followed by sulfur AA (SAA) (30%). These findings provide insight into the Cr content in extruded diets, prompting further investigation into the optimal Cr intake required to support AA and energy metabolism in cats.