Optimal
dietary protein and lipid levels for juvenile cobia (Rachycentron canadum)
Ruey-Liang Chou, Mao-Sen Su, Houng-Yung Chen-2001
Aquaculture, 193 (1-2): 81-89
Abstract:
Two growth trials were conducted to investigate the
optimal concentrations of dietary protein and lipid for cobia, a pelagic
fish showing great potential for offshore cage culture in tropical and
subtropical waters. In the first trial, casein was added to a fish
meal-based basal diet to replace starch to render protein concentration
gradation ranging between 36% to 60%. All seven diets were estimated to be
isoenergetic. After an 8-week growth trial, juvenile cobia (initial weight
33 g) fed the diets containing protein concentrations of 44%, 48% and 52%
generally attained higher weight gain and feed conversion than the other
groups. Polynomial regression analysis revealed a weight gain peak at a
dietary protein concentration of 44.5%, which is regarded as the most
suitable level for maximum fish growth. In the second trial, the cobia were
fed seven isonitrogenous and isoenergetic test diets containing lipid
concentrations ranging from% 3 to 18%. Growth of the fish (initial weight 41
g) was lowest when the dietary lipid concentration was 3%. Weigh gain
increased with increasing lipid inclusion and then leveled off. The
broken-line analysis that best expressed the response pattern shows a
breakpoint when dietary lipid concentration was 5.76%. No significant growth
enhancement was observed when the lipid levels were increased beyond the
breakpoint to the highest lipid concentration tested (18%).
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