Reevaluation of the optimum dietary protein level for the maximum growth of juvenile Korean rockfish, Sebastes schlegeli (Hilgendorf)
2001
Kim, K.W. | Wang, X.J. | Bai, S.C.
This experiment was conducted to reevaluate the optimum dietary protein level for the maximum growth of juvenile Korean rockfish, Sebastes schlegeli (Hilgendorf). Lyophilized rockfish muscle and casein were used as the major protein sources in the basal diet. After 1 week of the conditioning period, triplicate groups of 20 fish averaging 7.3 +/- 0.04 g (mean +/- SD) were fed one of five semipurified diets containing the graded levels of 35%, 40%, 45%, 50% or 60% crude protein (CP). After 8 weeks of the feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed 60% CP diet were significantly higher than those of fish fed 45%, 40% and 35% CP diets. There was no significant difference in WG and SGR between fish fed 60% and 50%, and between fish fed 50% and 45%. Fish fed 60%, 50% and 45% CP diets had a higher feed efficiency ratio (FER) than did fish fed 40% and 35% CP diets. There was no significant difference in FER between fish fed 40% and 35% CP diets, and among fish fed 60%, 50% and 45% CP diets. Protein efficiency ratio (PER) was inversely related to the dietary protein level in a linear fashion. Whole-body protein and fat content were negatively correlated, and ash content was not affected by varying dietary protein levels. Broken-line analysis indicated that the optimum dietary protein level could be 48.6% +/- 3.45% (mean +/- SD) for maximum WG in this study. Therefore, these findings suggest that the optimum dietary protein level for maximum growth could be equal to or greater than 48.6%, but less than 50% CP containing 16.7 kJ g(-1) in juvenile Korean rockfish.
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