Synergistic carbon source utilization in Biofloc aquaculture of common carp (Cyprinus carpio): impacts on growth, health, and environmental parameters

Introduction Biofloc technology (BFT) offers a sustainable approach to aquaculture by enhancing water quality and nutrient utilization. This study investigated the effects of varying carbon-to-nitrogen ratios, achieved through different combinations of jaggery and corn flour, rice flour, or rice bran, on the growth performance, body composition, histological health, and immune response of common carp ( Cyprinus carpio ) fingerlings in a BFT system. Methods A 90-day experiment was conducted using common carp fingerlings, where different groups were fed diets supplemented with jaggery in combination with either corn flour, rice flour, or rice bran, creating varying C:N ratios. Water quality parameters, Biofloc volume, growth performance (final weight, weight gain, specific growth rate), body composition (crude protein, crude lipid), histological analysis of liver and intestine, Biofloc morphology, and immune-related gene expression were assessed. Results The addition of carbon sources, particularly jaggery and rice flour, significantly improved water quality by reducing total ammonia nitrogen, nitrite, and nitrate levels, and increasing Biofloc volume. The jaggery and rice flour group exhibited the highest final weight, weight gain, specific growth rate, and levels of crude protein and crude lipid. Histological analysis showed improved hepatic and intestinal health in this group. Biofloc morphology varied, with rod shapes observed in the jaggery and rice flour group and spherical peanut shapes in the jaggery and corn flour group. The jaggery and rice flour group also demonstrated elevated expression of immune-related genes. Discussion The combination of jaggery and rice flour provided an optimal C:N ratio, leading to enhanced water quality, improved growth performance, better body composition, healthier histological structure, and a strengthened immune response in common carp fingerlings. The unique Biofloc morphology and increased immune gene expression observed in this group suggest a synergistic effect of jaggery and rice flour in promoting a robust and efficient BFT system for common carp aquaculture.