Abstract
Due to the increasing trend in aquaculture and fisheries production, conventional feed resources, especially protein ingredients, are overburdened, and sometimes their price fluctuations limit quality feed formulations for farmers, thus leading to the exploration of alternative protein feed resources. Antarctic krill meal (AKM) has emerged as a potential candidate ingredient for sustainable and suitable partial replacement of conventional fish meal. A 10-week feeding trial was designed to investigate the effects of different concentrations of AKM on the growth performance, antioxidant capacity, and serum biochemical indices of coho salmon ( Oncorhynchus kisutch ) post-smolts. In total, 150 post-smolt fish with an average initial weight of 178.17 ± 0.73 g were divided into five groups with three replicates in each group and 10 fish in each replicate. Five experimental diets were formulated by substituting 0%, 3%, 6%, 9%, and 12% fish meal (protein source) with AKM (protein source), which were designated AKM0 (the control), AKM3, AKM6, AKM9, and AKM12, respectively. The results showed that the addition of AKM to the salmon diet increased (P < 0.05) the weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). There was no effect (P > 0.05) on body composition and essential amino acid profile of the meat except for methionine, isoleucine, lysine, and threonine. The liver concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and malondialdehyde (MDA) significantly decreased while the concentration of catalase and superoxide dismutase (SOD) increased in the AKM supplemented groups compared to the control group. The serum concentrations of ALT and AST decreased (P < 0.05) while total cholesterol, triglyceride, and total protein content increased (P < 0.05) in the AKM treatment groups compared to the control. Based on the results of this study, supported by polynomial quadratic regression analyses of WG, SGR, FCR, and PER, we conclude that 6.73%–7.08% AKM is the best possible suitable inclusion level range to partially replace conventional fish meal in the diet of coho salmon post-smolt.