Brown sugar addition enhanced nutrient removal rates, growth performance, and bacterial community in a rice straw-based biofloc shrimp culture system

A 30-day culture trial was executed to ascertain the effects of brown sugar addition on nutrient removal, feed conversion ratio, growth performance, and microbial community in a rice straw-based biofloc shrimp system. Twelve indoor experimental barrels were supplied with juvenile pacific white shrimp (Litopenaeus vannamei) with a preliminary mean weight of ∼1.08 ± 0.35 g. The experimental groups comprised four biofloc treatments labeled as (Control-CT, SG1, SG2, and SG3), each with three replicates. The SG groups were the treatments with varying amounts of carbon source (brown sugar) addition. Each experimental barrel was stocked with 100 juvenile shrimps. To maintain the carbon: nitrogen ratio, brown sugar was added daily in varying amounts in the SG treatments but not in the control group (CT). The results demonstrated that the ammonium and nitrite‑nitrogen concentrations in the SG3 (0.45 and 0.34 mg/L) and SG2 (0.58 and 0.43 mg/L) groups were significantly (p < 0.05) lower than the Control (1.18 and 0.88 mg/L). Also, the highest nutrient removal rates for ammonium nitrogen (80%) and nitrite nitrogen (83.79%) were observed in the SG3 treatment. In addition, the SG2 group's feed conversion ratio (0.66) was statistically (p < 0.05) lower than the CT group's (0.83). Compared to the control setup (86%), the SG treatments recorded shrimp survival rates of over 90%. Furthermore, our results revealed that the most dominant microbial phyla in all treatments were Proteobacteria (71.60%), Bacteroidetes (26.60%), Actinobacteria (18.53%), Planctomycetes (8.30%), and Verrucomicrobia (2.40%) which played a significant role in nutrient cycling and promoting water quality. Overall, our study highlighted an innovative ecological farming system that recycles agricultural waste, minimizes inorganic nitrogen levels, and serves as an in-situ food source for sustainable shrimp production.