In Vivo Protein Digestibility and Metabolic Differences of Muscle from Three Shrimp and Crab Species

This study compared the digestive utilization and metabolic responses of muscle proteins from Eriocheir sinensis (EM), Litopenaeus vannamei (SM), and Procambarus clarkii (LM) in a rat model. Nitrogen digestibility was assessed by the titanium dioxide indicator method, combined with serum biochemistry, renal histology, intestinal particle size, and metabolomics. All protein groups significantly increased body weight vs protein-free control, with EM showing the greatest growth and protein efficiency ratio. Digestibility did not differ among the three groups. EM had the highest apparent ileal digestibility; EM and SM had similar true ileal digestibility, both higher than LM. Metabolomics identified 2,072 metabolites, enriched in amino acid and protein digestion pathways. Species-specific differences in lipid and antioxidant pathways: EM affected arachidonic acid, LM modulated linoleic acid, and SM involved ascorbate. Both SM and LM showed reduced amino acid utilization. These findings provide a mechanistic basis for refined evaluation and utilization of crustacean proteins.