Effects Of Low Molecular Weight Chitosan On Growth,Metabolism And Immunity Of Carp Cyprinus Carpio

The effects of low molecular weight chitosan (LMWC) on growth, metabolism and immuntiy of carp Cyprinus carpio were investigated in the study. First of all, Based on single factor concentration gradient method, the fish were divided randomly into five equal groups of six animals each:(1) the basic diet group (control group),(2)0.25%LMWC group (0.25%LMWC was added to the basic deit),(3)0.5%LMWC group,(4)0.75%LMWC group, and (5)1.0%LMWC group. The carp physiological indicators (rate of weight gain and feeding coefficient) and digestive enzymes (hepatic and intestinal amylase, lipase, trypsin) indicators were examined after the carp were fed the basal diet and different concentrations of LMWC feed. The glucose metabolism indicators (blood glucose levels, liver and musscle glycogen) were also studied in the fish that had been fed different concentrations of the LMWC feed for60d, followed by a starvation periods of1,3,5and15d. After the effects of LMWC feed on carp growth and metabolism were investigated, the impacts of different concentrations of LMWC feed on hepatic and blood serum llmmune enzymes(SOD, ACP, AKP, PO) at different times (30,45,60d) were assessed.(1) With increasing concentration of LMWC and feeding time, the weight gain rates and the activity of amylase, lipase and trypsin increased gradually compared with the control, while such an increasing trend in1.0%LMWC group was less obvious. It was suggested that the influences of different percentages of LMWC in diet on the growth and digestive enzyme activities of C. carpio were different.(2) The blood sugar levels, liver glycogen content and muscle glycogen content showed a decreasing trend in animals that were fed different concentrations of LMWC feed following by starvation, reaching the minimum after15d of starvation; A significant diffiference in blood glucose concentration was found in the group starved for1and15d, while glycogen content in animals starved for1,3,5and15d was significantly different from that of the control group. The muscle glycogen content in fish deprived of food for1,3and7d after being fed high concentrations of LMWC group registered a significantchange.(3) With increasing concentration of LMWC and feeding time, hepatic ACP and AKP activity and blood serum ACP, AKP, and PO activity, but not SOD activity, gradually increased. Diet containing1.0%LMWC is the best for carp immune activity.Conclutions:(1) Diet containing different percentages of LMWC promoted carp growth and the activity of digestive enzymes, The most suitable ratio of LMWC in the basic diet was found to be0.75%.(2) Starvation for different durations after feeding different concentrations of LMWC for60d, the glucose levels and glycogen content showed a good stability, while the liver glycogen declined faster than that in musscle, the effect of starvation on carps was less obvious in the high LMWC groups compared to control, indicating that liver glycogen was the main energy source during short-term starvation. LMWC has some effect on the energy metabolism of carps, which can enhance the anti-starvation ability of carps and slow the loss of nutrition.(3) With different percentages of LMWC at different stages of experiment, the activities of SOD, ACP, AKP and PO of tested fish were increased and showed a concentration and time effect, indicating that LMWC can be used as an immunostimulant in aquatic green additives.