Dietary calcium requirements of bighead carp (Aristichthys nobilis)

To investigate the dietary calcium requirement of bighead carp (Aristichthys nobilis), six purified diets were formulated to contain different concentrations of calcium (0.09% (control), 0.43%, 0.76%, 1.12%, 1.44%, and 1.79% of dry diets). Each diet was hand-fed to triplicate 30 fish with average initial body weight (3.31 +/- 0.09 g) for 60 days. The results showed that weight gain (WG) and specific growth rate (SGR) significantly increased when the dietary calcium level was from 0.09% to 0.76% (P < 0.05). The phosphorus and calcium contents of the whole fish body were highest in the 0.76% and 1.12% groups, respectively (P < 0.05). The serum phosphorus content in the 1.79% group was significantly lower than in other groups (P < 0.05). As dietary calcium content was from 0.09% to 0.76%, the activities of lipase and proteinase in the intestine significantly increased (P < 0.05). In contrast, the glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) activities were significantly decreased (P < 0.05). Based on quadratic curve model analysis with WG and WGR as the appraising criteria, the appropriate dietary requirement of calcium for the bighead carp larvae (3.31 +/- 0.09 g) was 1.01% - 1.02%.