Abstract:A growth experiment was conducted to determine the optimal dietary protein to energy (P/E) ratio for juvenile tiger puffer (Takifugu rubripes) (initial average weight 14.95 g). Nine practical diets were formulated to contain three protein levels (36%, 42% and 48%), and three lipid levels (8%, 12% and 16%) in order to produce a range of P/E ratios (from 17.06 to 24.20 mg/kJ). Fish meal and soybean meal were used as main protein sources, and fish oil were used as the main oil source. Each diet was randomly assigned to triplicate groups of 30 fish with (14.95±0.37) g, stocked in polyethylene tanks (0.7 m×0.7 m× 0.4 m) supplied with a flow through seawater. Fish were fed by hand to apparent satiation twice daily (08:00 and 17:00). During the feeding trial, water temperature ranged from 24℃ to 28℃, salinity from 30 to 31, pH from 7.4 to 8.2, and dissolved oxygen from 5 to 7 mg/L. Juvenile tiger puffer was fed the experimental diets for 56 days. Based on two-way analysis of variance, the protein level, lipid level and protein to energy ratio of feed significantly affected the final weight, feed efficiency ratio (FER) and specific growth rate (SGR) (P<0.05). Those three growth parameters in the 42% and 48% protein groups was significantly higher than that in the 36% protein group (P<0.05), but there was no significant difference in the 42% and 48% protein groups (P>0.05). Those three growth parameters in the 8% lipid group was significantly lower than that of the 12% lipid group (P<0.05), while no significant difference was observed between the 12% and 16% lipid groups (P>0.05). In addition, there was no significant interaction between feed protein and fat levels on growth-related indexes. One-way analysis of variance showed that the final weight, FER, and SGR were the highest in the Diet8 (48/12) treatment, which were significantly higher than those in the Diet1 (36/8), Diet2 (36/12), and Diet3 (36/16) treatments (P<0.05), and was no significant difference compared with the Diet4 (42/8), Diet5 (42/12), Diet6 (42/16), and Diet7 (48/8) treatments (P>0.05). Considering growth performance and protein saving effect, these results suggest that the diet containing 42% protein and 12% lipid with P/E of 20.75 mg/kJ is optimal for juvenile tiger puffer.
