Effect of replacement of dietary fish meal with silkworm pupae meal on growth performance, body composition, intestinal protease activity and health status in juvenile Jian carp (Cyprinus carpio var. Jian)

This study investigated the effect of replacement of graded dietary fish meal (FM) protein (0, 50%, 60%, 70% and 80%) with silkworm pupae meal (SP) in juvenile Jian carp. Triplicate groups comprising 18 fish (15.96 +/- 0.66g) were fed one of five isonitrogenous and isocaloric diets (designated SP0, SP50, SP60, SP70 or SP80) for 8weeks. The final body weight and specific growth rate of fish in the SP60, SP70 and SP80 groups were significantly lower than those for fish in the SP0 group (P<0.05). The muscle protein content in the SP50 group was significantly higher than in the SP80 group (P<0.05). With increasing FM replacement levels, the hepatic superoxide dismutase (SOD) activity decreased and the malondialdehyde (MDA) content increased among the groups, with the significant difference appeared in SP80 group. The gene expression level of heat shock protein 70 in the SP70 group was significantly higher than in the SP0 group (P<0.05), while that in the SP80 group was significantly less than in the SP70 group (P<0.05). Significantly decreased intestinal protease activity, increased serum ALT and AST activities, irregular-shaped hepatocytes and intestinal microvilli were found in the SP80 group. The study demonstrates that it is practical to replace 50% of the Jian carp dietary FM protein with SP, higher SP levels are not recommended and that oxidation status of the SP should be carefully assessed.