Optimum dietary protein level for maximum growth of juvenile yellow puffer

Abstract

Six isocaloric diets containing 30, 40, 45, 50, 55 and 60% crude protein (CP) were fed to juvenile yellow puffer Takifugu obscyrus to determine their optimum dietary level of protein. After a 12-week feeding trial, weight gain of fish fed 50% CP diet was not significantly different from that of fish fed 55% CP diet, but significantly higher (P<0.05) than that of fish fed 30, 40, 45 and 60% CP diet. Also, a broken-line model analysis for weight gain indicated that the optimum dietary protein level was 50 ± 3.7% (mean ± SD). Fish fed 50% CP also had the highest feed efficiency and hepatosomatic index. Condition factor increased with dietary protein level. No significant differences existed in haematocrit, hemoglobin and survival rate among the dietary treatments. Therefore, these findings suggest that the optimum protein level is approximately 50% of dry diet for maximum growth in juvenile yellow puffer.