Optimum dietary protein level for maximum growth of juvenile yellow puffer

Six isocaloric diets containing 30, 40, 45, 50, 55 and 60% crude protein (C P) were fed to juvenile yellow puffer Takifugu obscyrus to determine their optimum dietary level of protein. After a 12-week feeding trial, weight gai n 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 3 0, 40, 45 and 60% CP diet. Also, a broken-line model analysis for weight ga in indicated that the optimum dietary protein level was 50 +/- 3.7% (mean /- SD). Fish fed 50% CP also had the highest feed efficiency and hepatosoma tic index. Condition factor increased with dietary protein level. No signif icant differences existed in haematocrit, hemoglobin and survival rate amon g the dietary treatments. Therefore, these findings suggest that the optimu m protein level is approximately 50% of dry diet for maximum growth in juve nile yellow puffer.