Sugarcane bagasse improved growth performance, digestive enzyme activity, microbial dynamics, and mRNA transcripts of immune-, growth, and antioxidant -related genes of Litopenaeus vannamei in a zero-water exchange system

Pacific white shrimp (Litopenaeus vannamei) were grown in a biofloc rearing systems with (control treatment) or without sugarcane bagasse (SB treatment), with 3 replicate systems per treatment. SB, is an economic carbohydrate source. Parameters monitored were water-quality, growth indices, digestive enzymes activity, and microbial dynamics. Messenger RNA levels of immune-related, growth-related, and antioxidant genes in hepatopancreas and muscle and gene's single nucleotide polymorphism (SNP) were also considered. The outdoor ponds (44.5 m3), were each stocked with 600 L. vannamei larvae with an initial weight of 0.024 g) to start a three-month experiment. The biofloc development was in two aerated active suspension tanks to which SB (about 700 g/day, adjusted every two weeks) was added to maintain the of the C/N at 16. The water quality parameters, digestive enzyme activity, growth, and survival (P ≤ 0.05) in the SB group was improved compared to the control. SB also increased the total heterotrophic microbiota compared to the control. The mRNA levels of immune- related genes (lipopolysaccharides/b-glucan- binding protein, β-glucan-binding protein, lysozyme, prophenoloxidase, crustin, transglutaminase, and hemocyanin) and antioxidant genes (superoxide dismutase and glutathione peroxidase) significantly increased in SB group (P ≤ 0.05) compared to the control treatment. The SB group was the highest in all growth- related genes such as insulin- like growth factors (I and II), growth hormone, myosin, and paramyosin. Eight SNPs were detected in the hemocyanin gene, and an adenine insertion (ins A-554) was recorded at a high body weight. Our findings implied that using SB, as a carbon source in biofloc system without artificial feeding, could improve water quality, growth indices, digestive enzymes, microbial dynamics and the mRNA levels of all immune-, growth- related and antioxidant genes in L. vannamei. •Biofloc technology with sugarcane bagasse as carbon source in L. vannamei farming.•Biofloc improved the water quality parameters and total heterotrophic bacteria.•Sugarcane bagasse group provides higher growth rate and survivability.•Sugarcane bagasse enhanced expressions of immune-related, growth-related, and antioxidant genes.•The hemocyanin gene may be used as a marker for high body weight.