Commercial shrimp feed in the grower phase typically contains 38-42% crude protein (CP). Meeting the amino acid (AA) requirements entirely by intact protein sources would not only result in excess amount dietary protein but also very costly. Formulating diets following ideal protein concept and using supplemental sources to meet the limiting AA are increasingly practiced as this strategy allows spare the dietary protein sources such as fish meal and thus, dietary protein content. The objective of this study was to evaluate the performance of whiteleg shrimp to varying levels of dietary protein balanced for amino acid profile using supplemental amino acids. In this regard, two trials were conducted, one in the tanks and the other in the commercial ponds in Vietnam.
For the tank study, a positive control diet containing high dietary protein level (40%), mimicking the industry standard diet with 14% fish meal level, was formulated. A set of treatment diets containing 38%, 36%, 34% and 32% crude protein levels was formulated by reducing the inclusion of intact protein sources such as fish meal and wheat gluten meal, while meeting our recommended amino acid levels using supplemental sources including AQUAVI® Met-Met, L-Lys and L-Thr. With this approach, the formulation cost of feed was gradually reduced with the increasing protein reduction, up to 20% between D40 and D32. Four tanks (800 L water volume) were randomly allotted to each dietary treatment. Each tank was stocked with 80 shrimp of 2.5 g mean weight (± 0.04 g, SD). Shrimp were fed with the respective diets to apparent satiation, 4 times daily over 56 days. Final body weight, growth rate, feed intake, FCR and survival did not differ among dietary treatments (Table 1). Net protein utilization (protein gain x 100 / protein intake) showed significant improvement in shrimp fed with the diet containing 34%CP versus those fed with the diets containing 36-40% CP
In the pond trial, the PC diet (40% CP) was compared with the 34% CP diet. In addition, two commercial diets with their CP level matching the PC diet were included. Each diet was fed to four randomly selected ponds (1000-1500 m2 area) and each pond was stocked with PL12-stage shrimp with a mean stocking density of ~60/m2. During the first 30 days, shrimp were fed with a common commercial control diet, followed by their respective treatment diets 3 times daily until 72-79 days of total production period. Results showed no significant differences among treatments in terms of body weight, FCR and yield. However, Evonik diets of both PC and the low protein diets showed 20% increase in the growth compared with the commercial diets. Economic analysis showed 34% CP diet was 10-48% more profitable compared with the PC diet and the commercial diets. Results overall indicate that shrimp do not need more than 34% crude protein in grower phase, when the dietary amino acids are balanced. Studies overall demonstrate the benefits of low protein diet (34% CP) in producing more profitable and sustainable shrimp farming.