On demand feeding and the response of Pacific white shrimp (Litopenaeus vannamei) to varying dietary protein levels in semi-intensive pond production

Feed is one of the primary costs associated with commercial production of Pacific white shrimp (Litopenaeus vannamei). This high cost is the combined outcome of feed cost and feed management. As feeding technology evolves, specifically the use of automated feeding systems, it is vital to reevaluate the optimal protein levels in diets for the best production outcomes. The use of passive acoustic monitoring (PAM) adds another level of complexity to how shrimp respond to feed because it has the potential to automatically adjust feed offerings based on protein because of the shrimp's response. In this research, four diets with various protein levels (40, 35, 30, and 25%) were fed to shrimp which were stocked (0.045 g, 25 shrimp/m2) into 16 ponds (0.1 ha) and cultured for an 85-day production cycle. Shrimp were fed on demand using an automatic feeding system with passive acoustic feedback. Final individual weights were significantly smaller for shrimp fed the 25% diet (31.22 g) compared to all other diets. The total biomass of all ponds ranged from 6928 to 7878 kg/ha for shrimp offered the 25%- 40% diets, respectively. Other than final weight, analysis of total biomass and all other production data showed no differences between treatments (p > 0.05). Whole-body analysis revealed significant differences in fat (p = 0.0002), copper (p = 0.018), and apparent net protein retention (p = 0.0025). Analysis of economic values indicated a statistically significant difference between treatments for feed cost (p = 0.020). The significantly lower individual weights from shrimp fed the 25% diet and the notably lower total biomass resulted in a subsequent difference in class size distribution. This ultimately led to a difference in the market value of shrimp ranging from $60,383 to $71,247. Although the 40% protein diet was significantly higher in cost it showed no differences in production or economic outcomes and higher level of water born TAN as compared to the other diets. Overall, these results indicate that a 30-35% protein diet would be the most efficient for use in pond production of Pacific white shrimp under the culture conditions examined in this study.