Effects of artificial compound feed, mixed feeding and cannibalism of conspecifics on growth performance, physiological status and metabolic gene expression in juvenile barramundi ( Lates calcarifer )

To optimize feeding strategies for juvenile barramundi ( Lates calcarifer ), this study compared the effects of cannibalism-based feeding (CB), formulated feed (FF), and a mixed feeding regime (MIX; formulated feed combined with biological feed) on growth performance, physio-logical responses, and immune-related gene expression. Thirty-six-day-old juveniles were randomly assigned to three treatment groups, with one L. calcarifer individual stocked per tank and 15 replicates per treatment, and reared for 20 days. In terms of growth performance, compared with the FF and CB groups, the weight gain rate (WGR: 862.31 ± 346.66) and specific growth rate (SGR: 93.2 ± 42.48) of the MIX group were significantly higher (p < 0.05), and the growth performance of the CB group was also better than that of the FF group (p < 0.05). In terms of physiological responses, the activities of alkaline phosphatase (AKP), pyruvate kinase (PK), alanine aminotransferase (ALT), and lipid peroxide (LPO) in the MIX group were significantly higher than those in the other two groups, while the activity of catalase (CAT) was significantly lower than that in the other two groups (p < 0.05). In terms of immune - related gene expression, the levels of lysosomal protease (cts1a) and the expression of the glycolytic gene eno3 in the CB group were significantly higher than those in the other two groups (p < 0.05), while the expression of heat shock protein 90 (hsp90), pro - inflammatory cytokine IL1β and the activity of superoxide dismutase (SOD) in the FF group were significantly higher than those in the other two groups (p < 0.05), indicating enhanced antioxidant and anti - inflammatory capabilities respectively. In conclusion, the MIX treatment promoted superior growth performance; however, the growth response was relatively unstable and was associated with potential risks of liver damage and oxidative stress. Cannibalism-based feeding (CB) may serve as an emergency nutritional strategy, although careful management is required to minimize its negative impacts. In contrast, the formulated feed (FF) treatment resulted in comparatively poor growth performance, with no significant improvement observed (P > 0.05). Overall, a mixed feeding strategy supplemented with immune enhancers is recommended for industrial-scale seed production to achieve a better balance between growth performance and fish health.