Biofloc technology and immune response of penaeid shrimp: A meta-analysis and meta-regression

Biological flocs develop as heterogenious communities of detritus, heterotrophic and autotrophic bacteria, algae, fungi and a variety of other things through appropriate management of the carbon-nitrogen ratio in aquaculture farming systems. These microbial communities improve the water quality, reduce the concentrations of toxic inorganic species, and act as a source of food and immunostimulants. However, the information about their role as immunostimulants is widely variable. To obtain a clearer view of the situation, it is necessary to summarize the current literature on this topic through a quantitative review analysis: a meta-analysis. The present work aims to evaluate the effect of biofloc technology (BFT) implementation on culture water quality through meta-analysis, meta-regression, and correlation analysis. Pubmed, Science Direct, Scopus, and Google Scholar were searched from 2000 to 2022 on the influence of BFT on immunological parameters. Three hundred and thirty-four of the scientific articles used BFT for penaeid shrimp, but only 25 articles met the inclusion criterion of using BFT to evaluate its effect on the shrimp's immunity. The current analysis found that the use of BFT stimulates all the evaluated immunological parameters. Also, meta-regression with fixed data of study parameters showed that slow-release carbon sources, probiotics, and an estimated carbon/nitrogen ratio of 10 potentiated a larger effect on BFT immune stimulation. The meta-analysis demonstrated that the volumes of the settleable solids (SS) and the total suspended solids (TSS) are crucial for the effect of BFT on the shrimp immune system. When TSS was higher than 294 mg/L, the respiratory metabolism of the shrimp was compromised. The analysis found evidence of publication biases, indicating that the data had to be interpreted carefully. Nonetheless, this meta-analysis shows that the data quality was sound and the approach used was appropriate; moreover, it also showed that BFT can be an environmentally friendly alternative culture method that enhances the shrimp's immune system.