Protein requirements in compounded diets for Penaeus vannamei juveniles

The average body weight of the juvenile Penaeus vannamei was (0.011±0.001) g. The main protein source of the experimental diets was supplied by casein and gelatin and the diets protein levels were designed at 28%, 33%, 38%, 43% and 48%, and two experiment salinity levels were 2 and 28. The experiment period was 49 d, during which the water temperature was 27.0-31.5 ℃, DO 4.5-5.6 mg/L and pH 7.8-8.3. The final results show that the feed conversion ratios and protein efficiency ratios both decrease with the increasing levels of dietary protein. The effects of dietary protein level on trypsin activities and essential amino acids compositions in shrimp muscle were significant(P0.05). The optimum level of dietary protein for P. vannamei juveniles is about 26.7% at salinity 2 with the weight gain of 9 844.27%, and at salinity 28 the optimum level of dietary protein is 33% at salinity 28 with the weight gain of 9 937.15%. The conclusion is that within certain range of dietary protein level, the diets with low protein level and high energy may get much high protein efficiency rate and good culture effects compared with high protein level diets.