Effects of fish meal replacement by soybean peptide on growth performance, digestive enzyme activities, and immune responses of yellow catfish Pelteobagrus fulvidraco

The present study was conducted to compare the effects of using soybean peptide as a particle substitution in fish meal on the growth performance, digestive function, and immune responses of yellow catfish. Four isonitrogenous and isoenergetic experimental diets were formulated by replacing 0 % (D-0), 20 % (D-20), 35 % (D-35), and 50 % (D-50) of fish meal with soybean peptide for 8 weeks. The results showed that the final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) significantly increased in the dietary D-50 group compared to those of the control group (D-0 group), and the feed conversion ratio (FCR) significantly decreased compared to that of other groups. The D-50 group had higher levels of serum globulin concentration (GLB), alkaline phosphatase activity (ALP), and total nitric oxide synthase activity (tNOS) than the control group, respectively. In addition, the anterior intestine protease activity of the D-20 group was significantly higher than that of the control group and the D-50 group. The serum alanine aminotransferase (ALT) activity of the D-20 dietary group was also significantly higher than that of other groups. Furthermore, the challenge with Aeromonas hydrophila caused mortality in all groups but it was lower in the group of fish that received D-50 than that of the control group. Therefore, we concluded that the D-50 diet could be used to improve immune responses and growth performance and to replace the fish meal in the diet of yellow catfish.