Effects of Low Salinity on Growth, Digestive Enzyme Activity, Antioxidant and Immune Status, and the Microbial Community of <i>Litopenaeus vannamei</i> in Biofloc Technology Aquaculture Systems

Biofloc technology (BFT) culture systems based on low salinity can meet the needs of shrimp growth and environmental protection, thus having potential application. To evaluate the effects of BFT on water quality, the microbial community, growth, digestive enzyme activity, and antioxidant and immune status of Litopenaeus vannamei under low salinity conditions, a four-week experiment was conducted in a BFT culture system (C/N ratio of 12: 1) with three salinity conditions: 5.0‰ (S5 group), 10.0‰ (S10 group), and 15.0‰. The results showed that water quality parameters were all within the range suitable for the culture of L. vannamei. There were no significant differences in growth parameters such as final weight or specific growth rate. Muscle moisture, crude protein, and crude lipid contents of L. vannamei did not differ among groups (p > 0.05). In addition, intestinal amylase and trypsin activities in the S5 group significantly increased (p L. vannamei, as well as serum catalase, acid phosphatase, and alkaline phosphatase activities, markedly increased (p L. vannamei in low-saline areas with BFT systems