Enhancing Muscle Quality in Largemouth Bass (Micropterus salmoides) through Temporary Rearing: An Inside-Out Purification Approach for Premium Yusheng

• Rearing with 5 mg/L GA for 7 to 21 days improved muscle quality, while caused adverse effect after 28 d. • Temporary feeding for 21 days could better maintain the integrity of intestinal structure. • The antioxidant activity of largemouth bass could be promoted with 5 mg/L GA reared for 21 d. • GA temporary rearing could affect the signal transmission of neurotransmitter gut microbiota axis. • The putrescine production pathway was mediated to improve muscle quality of largemouth bass. The quality of Yusheng (a raw fish delicacy) is a critical determinant of consumer acceptance. This study investigated the effect of 5 mg/L gallic acid (GA) on muscle quality of largemouth bass (Micropterus salmoides) , a key species for Yusheng production, based on the influence on the brain neurotransmitter-gut microbiota axis during 28 days of temporary rearing, with the muscle fiber morphology and intestinal structure being assessed every 7 days to evaluate potential improvements in muscle quality. Histological analysis revealed denser muscle fiber organization and more uniform myofibrillar structure in the 5 mg/L GA group; the better intestinal morphology structure was in the fish after 21 days of temporary rearing. The fish after 5 mg/L GA temporary rearing for 21 days exhibited significantly higher muscle pH, whiteness value and shear force along with a lower pressurized water loss rate, and the activities of superoxide dismutase and catalase and the contents of glutathione and malondialdehyde showed slowing down. Furthermore, integrated high-throughput analyses of neurotransmitters, gut microbiota, and muscle biomarkers revealed that GA induced alternation in the signal transmission of the neurotransmitter-gut microbiota axis, downregulated Ornithine Decarboxylase 1 ( ODC1 ) and Arginase 2 ( ARG2 ) expression, increased ornithine content, decreased arginine content and decreased putrescine production. The research demonstrated that temporary rearing with 5 mg/L GA for 21 days enhanced the muscle quality of largemouth bass through promoting antioxidant activities and induced alteration in signal transmission of the neurotransmitter gut microbiota axis to regulate the formation pathway of putrescine, which provides a theoretical basis for the systemic purification of premium Yusheng.