The effects of reducing the feeding rates on growth and feed performance, blood biochemical parameters, and water quality in bio-floc common carp (Cyprinus carpio) culture and clean systems

This study aimed to investigate the effect of reduction of feeding rates on water quality, growth performance, and immune response in bio-floc common carp (Cyprinus carpio) and clean water systems. Fish (9.04 ± 0.44 g mean initial weight) were stocked into 18 tanks (50 L) through a 2×3 factorial design consisting: The use of commercial feed of 100, 85 and 70% (2.5, 2.12 and 1.75 % of body weight) in bio-floc groups (BF1, BF2 and BF3) and non-floc groups (NF1, NF2 and NF3) for 60 days. At the end of the experiment, Total ammonia nitrogen (TAN) concentration was significantly lower in bio-floc compared to non-floc. The highest fish growth performance and the lowest feed conversion ratio were obtained in the bio-floc groups with 2.5 and 2.12% feed intake (BF1 and BF2), respectively. After 60 days, the serum lysozyme and total immunoglobulin levels were significantly increased and serum cortisol levels decreased in the bio-floc groups. This study showed that reducing the feeding rates (2.12 to 2.5% of body weight) have a positive effect on growth performance and immune response in bio-floc common carp culture system compared to clean water system.