Optimum protein requirement of juvenile Takifugu obscurus

YANG Zhou, YANG Jia-xin (School of Biological Sciences, Nanjing Normal University, Nanjing 210097, China)

Takifugu obscurus; optimum protein requirement; weight gain; feed efficiency; protein efficiency rate; broken-line model

It is important to study the nutrition requirement of Takifugu obscurus because the puffer is a precious and potential species for intensive aquaculture. A 12-week growth experiment was conducted in indoor concrete ponds to determine the optimum protein level for the growth of juvenile T. obscurus, at the temperature of 24-26℃. White fish meal was used as the sole protein source to formulate isocaloric experimental diets at six protein levels (35%, 40%, 45%, 50%, 55%, 60%). Weight gain and feed efficiency of fish improved with increasing dietary protein level up to 50% and reached a plateau above this level. Weight gain of fish fed 50% protein diet was significantly higher (P<0.05) than that of fish fed 35%, 40% and 45% protein diet, but not significantly different from that of fish fed 55% and 60% protein diet (P>0.05). The protein efficiency ratio tended to decrease with increasing dietary protein level, but there is no significant difference among the diets containing 35%, 40% and 50% protein levels (P>0.05). Dietary protein requirement using broken-line model was estimated at approximately 49% and 46% for maximum growth and maximum protein utilization, respectively. Therefore, it is suggested that the optimum dietary protein level for juvenile T. obscurus should be 46%-49%. The result is similar to that of tiger puffer T. rubripes.