Effects Of Low Molecular Weight Chitosan On Growth Metabolism Of Crayfish Procambarus Clarkii

Low molecular weight chitosan (LMWC) has many outstanding health benefits such as anti-oxidative, anti-bacterial, immunity regulation, and cholesterol lowering. This study aimed to examine the effect of dietary supplementation with LMWC on caryfish(Procambarus clarkii) digestive enzyme activities, antioxidant defense system, and lipid metabolism. Based on single factor concentration gradient method, the caryfish were divided randomly into five equal groups:(1) the basic deit group (control group),(2)0.25%LMWC group (0.25%LMWC were added to the basic deit),(3)0.50%LMWC group,(4)0.75%LMWC group and (5)1.00%LMWC group. The activities of amylase, lipase, trypsin and pepsin in the hepatopancreas, stomach and intestinal were analyzed after feeding for10d,20d and30d. The antioxidant defense system such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) were also studied in the caryfish that had been fed different concentrations of the LMWC feed for30,45, and60days. Otherwise, the indexes were measured in different treating times (30,45, and60d), which include the levels of hepatosomatic index, content of lipid and cholesterol in hepatopancreas, muscle and serum biochemical indexes (TG, TC, LDL-C, HDL-C). The results showed that:(1) When compared with control group, the activities of amylase, lipase, trypsin and pepsin showed a gradual upward trend for feed coefficient with increasing dietary LMWC supplementation and feeding time. For1.00%LMWC group, the digestive enzyme activities gradually slowed down with increasing feeding time.(2)0.75%LMWC group significantly increased SOD, CAT, GSH-Px activities and decreased MDA content in hepatopancreas and muscle of Procambarus clarkii compared with the control group. Different stages of the experiment, crayfish hepatopancreas and muscle changes in antioxidant enzyme activitiy that different diets the percentage of LMWC can increase SOD, CAT, and GSH-Px activity, and enhance antioxidant capacity of caryfish, also showed a concentration-effect manner.(3) With the elevated concentrations of LMWC and feeding time, the hepatosomatic index and the content of lipid and cholesterol in hepatopancreas and muscle were decreased gradually relative to the control. The LMWC groups decreased serum biochemical indexes of the crayfish compared with the control group. Especially, serum biochemical indexes in0.75%LMWC group significantly decreased at the time of60d than control group. In1.00%LMWC group, the decreasing levels of serum TG, TC, and LDL-C were slowly while there was no pronounced change of HDL-C level.Conclutions:(1) Dietary LMWC supplementation in different proportions had different effects on digestive enzyme activities in crayfish and the optimal dosage was0.50%.(2) LMWC had improved antioxidant capacity and inhibited lipid peroxidation content. LMWC can be used as an antioxidant aquaculture feed additives in the green.(3) The influences of the diets with different percentages of LMWC on the lipid metabolism of Procambarus clarkii were different. LMWC was shown to lower the level of cholesterol and TG level.