In this experiment, 500 healthy Procambarus clarkii (initial body weight: 3.00 ± 0.32 g) were selected as feeding subjects. The Procambarus clarkii were evenly and randomly allocated into five experimental groups (Groups A-E). Lysine was added to the Fishmeal-free feed at levels of 1.19 %, 1.50 %, 1.78 %, 2.10 %, and 2.38 %. The trial period is 45 days. The results showed that the body weight, weight gain (WG), weight gain rate (WGR), and specific growth rate (SGR) of male Procambarus clarkii in Group D reached the maximum value. The body weight, weight gain (WG), weight gain rate (WGR), and specific growth rate (SGR) of female Procambarus clarkii showed a gradually increasing trend, reaching the maximum value in Group E. The EAA and NEAA in the muscle tissues of both male and female Procambarus clarkii were higher in Group D compared to the other groups. qPCR analysis revealed that in males, the peak expression of mTOR and S6K1 was observed in Group B and Group C, respectively, while the peaks for 4E-BP1 and ALT occurred in Group D and Group E, respectively. The gene expression pattern in females differed from that in males: the peak expression of mTOR and 4E-BP1 was detected in Group D and Group E, respectively, whereas S6K1 and ALT peaked in Group E and Group C, respectively. In the hepatopancreas of male and female Procambarus clarkii , the activities of SOD, CAT, and ALT were higher in Group D compared to the other groups. In summary, supplementing fishmeal-free feed with 2.17–2.38 % lysine promotes the growth of Procambarus clarkii, enhances protein metabolism, and improves antioxidant capacity and immunity. • Lysine Supplementation in Fishmeal-Free Feeds improves the growth of Procambarus clarkii . • Lysine Supplementation in Fishmeal-Free Feeds enhances protein deposition and antioxidant capacity in Procambarus clarkii . • Lysine Supplementation in Fishmeal-Free Feeds strengthens the immune function of Procambarus clarkii
He et al. (2026) studied this question.