Effect of protein levels and different carbon sources on mucus immune parameters, hepatic enzymes activity and Lactobacillus loading in biofloc system of common carp (Cyprinus carpio) juvenile

An 8-week experiment was conducted to evaluate the effect of different carbon sources and protein levels on mucus immune parameters, hepatic enzymes and intestine lactic acid bacteria loading in biofloc system of common carp (Cyprinus carpio) juvenile in intensive culture. Fish fed the feed containing 20 or 30% crude protein including two groups in clear water conditions with no biofloc, two biofloc groups given a molasses as additional carbon source (M), two biofloc groups given rice bran (RB) and two biofloc groups given mixture of molasses + rice bran at equal weight ratio (M+RB). At the end of trial, mucus immune parameters (lysozyme activity and total immunoglobulin), hepatic enzymes (LDH, AST, ALT, ALP) and intestine lactic acid bacteria loading were investigated. The results showed that significant improvements in immune parameters were observed in fish fed 30% dietary protein and reared in biofloc condition (P<0.05). Hepatic enzymes and lactic acid bacteria loading significantly improved in fish fed 30% dietary protein and reared in M and M+RB biofloc than control group (P<0.05). In conclusion, using mixture of M+RB as carbon source associated higher protein can be improved immune response, metabolic enzyme and lactobacillus loading in intensive farming of common carp.