Estimation of Dietary Copper (Cu) Requirement of Cynoglossus semilaevis Guenther

摘要

To evaluate the dietary copper (Cu) requirement of Cynoglossus semilaevis, inorganic Cu (0,2,6,17, and 50 mg kg~(-1)) was added to the basal diet, providing actual dietary Cu (5.91, 8.23, 11.78, 24.16, and 56.34 mg kg~(-1)). Each diet was fed to C. semilaevis Guenther (initial body weight, 68 g) in triplicate groups for 8 weeks in a flow-through system. The results showed that weight gain rate (WGR), specific growth rate (SGR), feed conversion rate (FCR), and protein efficiency ratio (PER) in fish supplemented with 11.78 mg kg~(-1) were significantly higher than those in fish fed with the basal diet (P < 0.05), and no significant difference was observed in fish fed dietary Cu ranging from 11.78 to 56.34 mg kg~(-1) (P > 0.05). The activities of protease, amylase, lipase, copper-zinc superoxide dismutase (Cu-Zn SOD), and lysozyme first increased and then decreased with the increasing dietary Cu concentrations, and 11.78 mg kg~(-1) diet provided maximum activities. The optimum requirement of C. semilaevis for dietary Cu was estimated to be about 11-12 mg kg~(-1) diet using broken-line regression analysis, based on the growth and enzyme activities.