Dietary manganese requirement for juvenile cobia, Rachycentron canadum L.

A 10-week feeding trial was conducted to estimate the optimum dietary manganese requirement for juvenile cobia, Rachycentron canadum L. The basal diet was formulated to contain 501 g kg−1 crude protein from vitamin-free casein, gelatin and fish protein concentrate. Manganese sulphate was added to the basal diet at 0 (control group), 6, 12, 18, 24 and 36 mg Mn kg−1 diet providing 5.98, 7.23, 16.05, 23.87, 28.87 and 41.29 mg Mn kg−1 diet, respectively. Each diet was randomly fed to three replicate groups of cobia for 10 weeks, and each tank was stocked with 30 fish (initial weight, 6.27 ± 0.03 g). The manganese concentration in rearing water was monitored during the feeding period and was < 0.01 mg L−1. Dietary manganese level significantly influenced survival ratio ( SR), specific growth ratio ( SGR), feed efficiency ratio ( FER) and the manganese concentrations in the whole body, vertebra and liver of cobia. When the dietary manganese level rose from 5.98 mg kg−1 to 23.87 mg kg−1, the superoxide dismutase ( SOD; EC 1.15.1.1) activities in liver also increased ( P < 0.05). But there was no significant change in SOD activities for the groups fed with diets containing manganese level higher than 23.87 mg kg−1. On the basis of broken-line regression of SGR, manganese concentration in whole body and vertebra the manganese requirements of juvenile cobia were 21.72 mg kg−1, 22.38 mg kg−1 and 24.93 mg kg−1 diet in the form of manganese sulphate, respectively. [ABSTRACT FROM AUTHOR]