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A 28‐day experiment was carried out to evaluate different C/N ratios (10:1, 15:1 and 20:1) on growth performance, water quality, survival rate and gene expression related to metabolic pathways of Penaeus vannamei in a biofloc system. To maintain the C/N ratio of the feed input, different carbon sources (molasses, rice bran and wheat flour) in combination were applied after fermentation for a day with biofloc consortium. Results showed that shrimps reared in C/N 10 (630 mg) and C/N 15 (646 mg) biofloc systems showed significantly (p =.0229 and.0263) higher growth when compared to C/N 20 (528 mg) and control (374 mg). With regard to the production of extracellular enzymes, protease, lipase and xylanase were found predominantly in colonized bacteria isolated from biofloc treatments, whereas amylase was commonly found in all the treatments. The proPO activity was considerably increased in C/N 10 and 15 treatments than C/N 20 and control. The ranges of relative expression levels of potential genes entailed in metabolite pathway like hexokinase (HK‐ 6.57–8.17), pyruvate kinase (PK‐5.79–7.96), crustacean hyperglycaemic hormone (CHH‐ 6.99–7.66) and fatty acid synthase (FAS‐ 6.57–8.86), triacylglycerol lipase (TGL‐6.99–8.66) and immune gene (Toll receptor‐ 4.57–4.86) fold up‐regulated expression were observed in the biofloc treatments than that of the control. The overall findings indicate that the rearing of P. vannamei shrimp in C/N 10 and 15 biofloc systems could improve the growth performance, water quality and development of immune and metabolic responses. [ABSTRACT FROM AUTHOR]

A 16‐week indoor culture trial was conducted to evaluate the effect of varying C:N ratio on growth performance, physico‐chemical parameters, microbial dynamics, feed utilization, and immunological parameters. The experiment comprised of five biofloc treatment groups (with varying C:N ratio 5:1, 10:1, 15:1, 20:1) and a control with three replicates each, having 100 nos/m3 as stocking density in 500 L tanks with constant aeration. The C:N ratios of the treatments were manipulated using molasses as an organic carbon source whereas there was no carbon source added in control. The water quality parameters monitored throughout the experiment were found to be within permissible limits in shrimp culture. At the end of the experiment, it was observed that there were significant differences between the treatment groups and the control regarding absolute growth, SGR, FCR, PER, and FER. Furthermore, a considerable difference in immunological parameters, namely, THC, phagocytosis, and PO activity (17.5 × 106 cells per ml, 43.5%, 0.112 Units min−1 mg min−1), was recorded among the treatments compared to that of the control groups (6.2 × 106 cells per ml, 31.5%, 0.051 Units min−1 mg min−1) respectively. Enhanced growth and survival with substantial disease resistance were recorded in C15 treatment. The results indicate that the CN15 ratio coupled with minimal water exchange is optimal for improved survival, growth, and immune activity. [ABSTRACT FROM AUTHOR]

Soil and water interactions and their influence on growth and production in different densities ( SD8 & SD16) under zero water exchange were studied in two successive crops of Penaeus monodon in Tamil Nadu, India during 2007 and 2008. Scraping and tilling during pond preparation increased the mineralization rate than scraping only. During crop, there was no significant difference in soil organic carbon and total nitrogen between the SDs. However, as the crop progressed, organic carbon and total nitrogen content of the soil showed significant difference under both the SDs. Between the SDs, nitrate and phosphate content in water significantly differed, whereas the progress of the crop significantly increased both available and total nutrients. Mass balance of nitrogen indicated that applied feed contributed to 97.4-98.5% of input nitrogen, of which nitrogen in sediment accounted for 16.5-27.3%, nitrogen recovery in shrimp was 34.2-43.6% and the nitrogen lost through denitrification and volatilization varied from 4.7% to 34.7%. Zero water exchange system is highly efficient as nitrogen recovery is higher in shrimp and lower in discharge water. Lack of significant difference in metabolites between the SDs indicates the role of aeration and probiotics in sustaining SD16 cultures. [ABSTRACT FROM AUTHOR]