Protein is the most important nutrient in aquafeeds. Establishment of optimal dietary protein level is essential to maximize growth and to reduce feed costs and nitrogen excretion. However, the dietary protein requirement of P. chinensis remains unknown. This study was conducted to determine the dietary protein requirement of P. chinensis at post-larvae stage.
Six experimental diets were formulated to contain 25%, 30%, 35%, 40%, 45% and 50% crude protein (designated as P25, P30, P35, P40, P45 and P50, respectively). Total 360 shrimp (initial BW: 0.50 ± 0.01 g) were randomly stocked into 18 tanks (96 L) with 20 shrimp per tank. Triplicate groups of shrimp were fed one of the diets four times daily for 42 days.
Growth performance (final body weight, weight gain and specific growth rate) was significantly higher in P30, P35 and P40 groups than in P25 group. Feed conversion ratio was significantly lower in P40 group than in P25 group. Protein efficiency ratio was significantly higher in P40 group than in P25 group. Survival was not significantly different among all the groups. Superoxide dismutase activity was significantly higher in P35 and P40 groups than in P25, P30 and P50 groups. Glutathione peroxidase activity was significantly higher in P40 and P45 groups than in other groups.
The results suggests that dietary protein level of 35% seems adequate to promote growth performance, feed utilization and antioxidant capacity of P. chinensis post-larvae. Based on the results of broken-line regression of weight gain, the dietary protein requirement for P. chinensis was estimated to be 36.3%.