Effect of organic carbon source and stocking densities on growth indices, water microflora, and immune-related genes expression of Litopenaeus vannamei Larvae in intensive culture

Abstract The study conducted to evaluate the effect of different stocking densities in a biofloc (BF) system, with sugarcane bagasse as an organic carbon source on growth performance, immune response-related genes, and microbial biomass of shrimp larvae in a 90-days. Litopenaeus vannamei larvae (0.002 ± 0.01 g) were cultured in 12-tanks with different stocking densities (12 or 16 larvae/l), including two controls without a carbon source (12C and 16C) and two BF treatments without a commercial diet (12BF and 16BF) in triplicates. Based on the results, the total number of heterotrophic bacteria (THB) and Vibrio spp. counts (TVC) were positively affected by BF treatment. The highest THB value was recorded in treatment 12BF, whereas the lowest TVC value was recorded in 16BF. The highest (9.85 ± 1.60 g) and lowest (7.96 ± 2.72 g) weight gains were observed in 16BF and its control. Overall, the highest growth indices, survival rate and crude protein content were recorded in BF treatments. Furthermore, the expression of immunity-related genes were positively affected by BF treatment. However, the addition of agricultural by-product sugarcane bagasse as a carbon source in BF-tanks with zero-water exchange facilitated water recycling and increased the number of THB communities which could replace the commercial diet in BF-tanks and improve the growth and health of shrimp.