Discussion
Fishes in general utilize dietary lipid poorly. For instance,
Furuichi and Yone [9] noted depressed growth and feeding
efficiency in red sea bream, Pagrus major, and common carp,
Cyprinus carpio fed diets with high carbohydrate and low
lipid contents. The optimum level of dietary nutrients should
enhanced maximum growth and feed efficiency [10] and so
the decrease weight gain and the SGR may due to higher
energy content and high carbohydrate content in the diets [11,
12]. An inverse relationship between growth and dietary
energy was reported in juvenile red drum, Sciaenops ocellatus
[12]. Dietary carbohydrate and lipid levels of 12 and 20 %
are recommended for trout [13] and chinook salmon [14]
respectively. Habib et al. [15] demonstrated that 30 % carbohydrate
level and low protein levels were well suited for
silver barb, Puntius gonionotus, and 35 % carbohydrates with
low protein was well suited for Heteropneustes fossilis [16].
Mollah and Alam [17] reported that 15–20 % carbohydrate
level was well suited for Clarias batrachus. In terms of PER,
the protein is responsible for large part of the cost of most
prepared feeds. The expensive protein fraction should therefore
be optimally utilized for protein synthesis rather than for
energy by the fishes. Knowledge of the optimal level of protein
and protein-sparing effects of non-protein nutrients such
as lipids and carbohydrate can be used effectively in reducing
feed costs [10]. Our PER value is comparable with the values
of Daniels and Robinson [12]. Lin et al. [18] reported that
better SGR may have partly resulted from better carbohydrate
and lipid utilization by snakehead grow-out feeding strategyand carbohydrate source.