Growth performance and physiological responses of striped catfish (Pangasianodon hypophthalmus) under different carbohydrates supplemented biofloc aquaculture systems

Biofloc technology is booming in inland aquaculture sector across the world especially in the places where water scarcity is high and land cost is expensive. Currently, the lack of appropriate selection and application feasibility of suitable carbohydrate in water quality management and fish health in biofloc aquaculture system are the major concern for wider adaptability of the technology. Therefore, the present experiment investigated the effect of different carbohydrate sources on overall wellbeing of striped catfish (Pangasianodon hypophthalmus) fingerlings. The experiment was randomly designed in four treatments (T1, T2, T3 and T4) and one control in triplicates in indoor tanks (1.0 m(3)). T1, T2, T3 and T4 groups supplemented with tapioca flour, sugarcane bagasse, molasses and jaggery, respectively under biofloc system at C:N ratio of 15:1, whereas the control group was not supplemented with carbohydrate source. Pre-acclimatized 525 fingerlings (7.2 +/- 0.03 cm, 7.4 +/- 0.003 g) were randomly stocked (35 nos. m(-3)) in the tanks and reared for 90 days. Overall, better water quality, fish performance and health status were observed in all the carbohydrates supplemented treatments than the control. Higher abundance of heterotrophic bacteria (5.88-118.18%) and biofloc associated microorganisms in jaggery supplemented biofloc, significantly (P <= 0.05) reduced total ammonia nitrogen, nitrite-nitrogen, and increased nitrate-nitrogen concentrations than other treatments. In the T4 treatment, jaggery supplementation enhanced biofloc volume, which influenced enhancement of fish body weight gain, specific growth rate, and improvement of feed conversion ratio than other biofloc treatments. Enhanced gut microbial population and digestive enzymes activity in fish significantly enhanced protein efficiency ratio, apparent net protein utilization, and flesh protein content in the T4 treatment. Fish showed significantly (P <= 0.05) higher haematological, immunological, and improved antioxidative responses in the T4 treatment than other treatments. Consumption of biofloc significantly (P <= 0.05) improved intestinal villi microarchitecture as higher villi surface area, width and height were detected in the T4 treatment. Collectively, the findings suggested that jaggery was the suitable carbohydrate source in terms of overall improvement of the culture system including growth performance and health status of P. hypophthalmus, if applied appropriately in biofloc aquaculture system. The present study comprehensively addressed carbohydrate sources, biofloc formation, total ammonia nitrogen management, fish growth and health resulting in better adoptability of biofloc technology by farmers in aquaculture.