Effects of feed, carbohydrate addition and stocking density on Pacific white shrimp (Litopenaeus vannamei) production

Shrimp culture rearing systems are dynamic with numerous processes influencing system performance. This research investigated the effects of stocking density, feeding level and C:N ratio on shrimp production, water quality and microbial community composition in a biofloc shrimp rearing system, using a 3 x 3 factorial design. Pacific white shrimp (Litopenaeus vannamei) were stocked at 27, 120, or 300 individual m(-3) and fed 100, 80 or 60% of the recommended daily feed ration. For each combination of stocking density and feeding level, C:N ratios of 7.4, 12 or 16 were created by feeding a mixture of casava and rice bran besides the daily pelleted feed input to culture tanks. After 12 weeks of culture, the harvested shrimp biomass was the highest in the rearing tanks with the highest stocking density, feeding level and C:N ratio (P < 0.05), while the individual shrimp size at harvest decreased with increasing stocking density (P < 0.05). Biofloc biomass (e.g. total suspended solids TSS, volatile suspended solids VSS) and, to a lesser degree, water quality (total ammonia nitrogen TAN, NO2-N) were affected by 2 and 3-way interactions of the main tested factors. The ash, protein, fat and nitrogen free extract (NFE) content in biofloc were affected by stocking density (P < 0.05), and ash and NFE content by C:N ratio (P < 0.05). Regarding the microbial community composition in the biofloc at the highest stocking density, increasing feeding level and C:N ratio led to an increasing microbial richness and diversity (P < 0.05) as a result of nutrient input. Overall, the shrimp production and biofloc biomass were influenced in a similar way by the stocking density, feeding level and C:N ratio applied in the biofloc system. Future research should focus on how the type of carbohydrates and methods of administration affect shrimp growth and biofloc formation, and how this may promote health benefits through the microbial community manipulation.