Effects of Replacing Fishmeal With Antarctic Krill Meal on Nutrient Deposition, Metabolism, and Immunity in Silver Pomfret (Pampus argenteus).

Although silver pomfret (Pampus argenteus) is a highly valued marine fish in China, its aquaculture development is limited by the lack of species-specific formulated feed. This study investigated the effects of replacing fishmeal with Antarctic krill (Euphausia superba) meal (AKM) on the nutritional deposition, metabolism, and immune response of silver pomfret. Juvenile fish with an initial body weight of 12.93 ± 0.48 g were randomly allocated into four dietary treatments with three replicates per treatment (50 fish per tank; 600 fish in total), and fed one of four experimental diets containing 0% (FM), 10% (KM10), 20% (KM20), or 40% (KM40) AKM for a 60-day feeding trial. The results showed that moderate AKM inclusion, particularly at the 20% replacement genes (pparα, cpt1α) and the downregulation of lipid level significantly enhanced intestinal trypsin and lipase activities, as well as glucose and amino acid metabolic capacity. In addition, lipid utilization efficiency was improved through the upregulation of fatty acid oxidation-related genes (fas). Consequently, the KM20 group exhibited significantly higher muscle essential amino acids and polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), compared to the FM group (p < 0.05). Furthermore, serum immunoglobulin M (IgM), complement C3, and C4 levels increased in AKM-fed groups, with KM20 showing the most pronounced enhancement. However, excessive substitution (KM40) led to a decline in certain nutritional and immune parameters, suggesting potential metabolic imbalances. These findings indicate that moderate replacement of fishmeal with AKM (~20%) optimizes nutrient deposition, enhances metabolic efficiency, and boosts immune capacity in silver pomfret. This study provides a theoretical basis for the development of functional aquafeeds aimed at promoting the sustainable and efficient industrial cultivation of silver pomfret.