Effects of adding molasses in water and diet of common carp on growth, blood biochemical indices, digestive enzymes and water quality in a biofloc system

This study was carried out to evaluate the effects of adding molasses (in water and diet) on growth performance, digestive enzyme activity and non-specific immunity of Cyprinus carpio in a biofloc system. Common carp (12.06± 0.35 g mean initial weight) were cultured in 3 treatments with triplicate for 7 weeks with daily addition of sugar beet molasses as carbon source to maintain the C/N ratio (1:15) which included: addition molasses to water (MW) and feed (MF) in biofloc system and clean water control without molasses addition (control). There was no statistically significant difference in water quality (ammonia and nitrate) between different experimental treatments. The growth and feed performance were significantly higher in the receiving molasses treatment than the control (P<0.05). The digestive enzymes of amylase, lipase and protease had a significant statistical difference between experimental treatments (P<0.05). Protease activity was significantly higher in MW and MF treatments than control. Plasma immunoglobulin and lysozyme levels of fish cultured were significantly higher in the biofloc system (MW and MF) than in the control, whereas plasma cortisol was significantly lower in receiving molasses treatment. Overall, the present findings suggested that molasses can be taken into account as functional feed additives for Cyprinus carpio.