Determining the appropriate level of protein in diet of Cyprinus carpio fry based on some parameters of growth, blood and serum biochemistry in biofloc system

The present study was conducted to determine the appropriate level of protein in diet of Cyprinus carpio fry based on biofloc technology. The experiment was designed based on triplicate of four bioflocs treatments (BFT) and one control treatment (CW). 450 specimens of C. carpio fry with mean weight of 17±0.08 g were stocked in 15 fiberglass tanks. Fish were fed in biofloc treatments with diets containing 23% crude protein (CP) (BFT-23%), 27% CP (BFT-27%), 31% CP (BFT-31%) and 35% CP (BFT-35%). Sugar beet molasses was added as a carbon material to development the biofloc. Fry were fed with 35% CP (CW-35%) in non-biofloc control treatment. According to obtained results, weight gain, specific growth rate, daily growth and protein efficiency rate were significantly higher in BFT-31% and BFT-27% than other treatments (P<0.05). Protein level of diet had significant effect on some parameters of blood and serum biochemistry (red blood cells, white blood cells, hematocrit, hemoglobin, total protein and albumin) in bifloc treatments and their rates in BFT-31% and BFT-35% treatments were significantly higher than other treatments (P<0.05). Results of this research indicated that diet protein level can decrease from 35% to 27% without any effect on survival, growth, feed conversion ratio and some parameters of blood and serum chemistry when Cyprinus carpio fry culture in biofloc system, and shows that biofloc system can help to protein feeding and physiological health of Cyprinus carpio.