Dietary lysine facilitates muscle growth and mediates flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in low-salinity water

To investigate the effect of dietary lysine levels on the growth performance and flesh quality of Pacific white shrimp (Litopenaeus vannamei) reared in low-salinity water (2.5 parts per thousand), shrimps with an initial body weight of (1.70 +/- 0.02) g were fed three diets with lysine levels of 9.60, 24.94, and 34.71 g kg(-1) respectively for 56 days. The results showed that the weight gain and flesh percentage were significantly increased (P < 0.05) at the lysine level of 24.94 g kg(-1). The diet with 24.94 g kg(-1) lysine promoted the conversion of fast myofibers into slow myofibers, increased myofiber density, and thus increased muscle hardness. Lysine deficiency (9.60 g kg(-1)) resulted in reduced muscular crude protein content, total hydrolyzed amino acid content, and antioxidant capacity (P < 0.05). Optimal lysine levels (24.94 g kg(-1)) increased total flavor amino acid content by increasing muscular free alanine and glutamate contents. Untargeted metabolic analysis based on the muscle showed that the differential metabolic pathway was glutathione metabolism among these three groups. Overall, the diet containing 24.94 g kg(-1) lysine improves muscle growth and mediates the flesh quality of L. vannamei reared in low-salinity water by affecting muscle hardness, nutritional values, flavor, and antioxidant capacity.