Influence of Different Stocking Density and C/N ratio on Growth Performance, Feed Utilization and Digestive Enzyme Activities of the Pacific White Shrimp (Litopenaeus vannamei) in a Biofloc System

The purpose of the following study was to use the “biofloc system” in different stocking densities and C/N ratios, analyzing the zootechnical performance, the nutritional composition of the formed biofocs, digestive enzymes and the economic evaluation of the white shrimp for 56 days. For this study, 36 tanks were used. Stocking densities were 10, 20, and 30 shrimp/100L (average initial weight, 0.6± 0.23g). Molasses was added as a carbon source to culture tanks to achieve C/N ratios of 10, 15, or 20 for each stocking density group, along with the daily amount of commercial feed. Following 56 days of culture, the maximum growth rate of shrimp was produced in the tanks with the C/N ratio (15:1) at all the stocking densities (P < 0.05). On the contrary, both the C/N ratio and stocking densities increased, while the feed conversion ratio (FCR) decreased (P < 0.05). The BFT system showed little effect on the shrimp's body. However, the increasing C/N ratio (20:1) showed a significant change in the crude lipid in the shrimp's body. Molasses addition led to a considerable enhancement in the formation of the produced biofloc. Overall, all the protease, lipase and amylase activities were influenced by the microorganisms applied in the BFT system. However, the C/N ratio (15:1) recorded the best digestive enzymes activities in the hepatopancreas of cultured shrimp. The study's findings show that adjusting the C/N ratio (15:1) with low or medium stocking density can have a considerable impact on shrimp performance, feed utilization, and digestive enzymes. Using BFT system as an in-situ food source produces benefits that are similar to those of conventional systems, without the associated economic costs.