Effect of replacing a portion of fish meal with unfermented and/or fermented soybean meal on the growth performance, antioxidant and immunity capacity and related gene expression in juvenile Coho Salmon, Oncorhynchus kisutch

This study investigated the effect of replacing a portion of fish meal with unfermented and/or fermented soybean meal in juvenile coho salmon (Oncorhynchus kisutch). Four groups of juveniles (initial weight 110.31 ± 3.12 g) in triplicate were fed for 90 days on four different iso-nitrogen and iso-lipid diets. The G0 diet comprised 28% fish meal protein (control group). In the other three diets (G1, G2, and G3), 10% of the fish meal protein was replaced with unfermented and/or fermented soybean meal protein. The main results were: Compared with G0, the WGR, SGR, CF; the contents of GLU, TP, ALB, T-CHO, and T-AOC, the activities of AKP, CAT, SOD, GST, GSH-PX, O₂·-CR, OH·-CR, and GSH and the expressions of SOD, GSH-PX, GST, CAT, and Nrf2 genes of juvenile coho salmon in G3 were significantly (p < 0.05) increased, However, the FCR, HSI, the content of MDA, and the expressions of TNF-α and IL-6 genes of juvenile coho salmon in G3 were significantly (p < 0.05) decreased. There was no significant effect (p > 0.05) of diet on their survival rate (SR). In conclusion, the fermented soybean meal in the juvenile coho salmon diet can replace 10% of the fish meal protein.