| 1Effect of dietary carbohydrate-to-lipid ratios on growth, physiology and biochemisty by the juvenile Australian redclaw crayfish, Cherax quadricarinatus (Von Martens)Australian red claw crayfish Cherax quadricarinatus is considered to be a popular freshwater crustacean species for aquaculture due to its potential large side, fast growth rate, good taste and unaggressive behavior. A growth experiment was conducted to determine the optimal carbohydrate-to-lipid (CHO:L) ratio for juvenile Australian redclaw crayfish (initial weight1.72±0.01g (mean±S.D.)) cultured in indoor recirculing aquaculture system. Five isonitrogenous (31.13±0.004g/kg) and around isoenergetic (17.49±0.396MJ kg-1) diets with dietary CHO:L ratios:10.75,4.81,2.66,1.52and0.87, were fed twice a day to apparent satiation.1.1Over8-week growth trial, the best final weight, weight gain, specific growth rate and feed conversion ratio value (P<0.05) were observed in redclaw crayfish fed diets with a CHO:L ratio of2.66. Redclaw crayfish fed either the lowest (0.87:1) or highest (10.75) CHO:L ratio tended to produce lower growth and poorer feed conversion ratio. Based on a second-order polynomial regression analysis of WG against dietary carbohydrate and lipid levels, growth maxima was observed when the dietary carbohydrate and lipid levels were268.82g/kg and122.20g/kg, corresponding to a CHO:L ratio of2.20. These results indicated that the utilization of dietary lipid and carbohydrate was moderate in redclaw crayfish and the preferential utilization of carbohydrate was over that of lipid.1.2Over8-week, dietary lipid levels was40～145g/kg, the lipase and alkaline phosphatase activities were stimulated by elevated levels of dietary lipid. However, the activities of hexokinase and pyruvate kinase showed opposite trend. The pepsin and intestine amylase activities were significantly (P<0.01) affected by CHO:L ratios. The higher activity of Pepsin were observed when the CHO:L were2.66:1and1.52 (P<0.05). The intestine amylase activity was significantly increased (P<0.05) as dietary CHO levels (156.3g/kg～360.4g/kg) increased.1.3Over8-week trial, Lipid deposition in the tail muscle decreased as the dietary CHO.L ratio increased (P<0.05), and the highest lipid deposition occurred in redclaw crayfish fed the lowest CHO:L ratio diet. Hepatopancreatic glycogen content was significantly higher (P<0.05) in the specimens fed with the2.66:1CHO:L ratio diet than with the other diets. Plasma glucose, plasma total cholesterol, and triacylglycerol contents were also significantly (P<0.05) affected by the CHO:L ratios in the diets. The plasma glucose content significantly decreased (P<0.05) as dietary CHO:L ratios decreased. However, the plasma total cholesterol and triacylglycerol contents showed the opposite trend. Plasma total cholesterol levels increased linearly as dietary CHO:L ratios decreased. Plasma triacylglycerol content of the specimens fed the diet with the lowest CHO:L ratio was significantly higher (P<0.05) than that of specimens in the other treatments.2The effect of starvation and compensatory growth on growth, physiology and biochemisty in Australian redclaw crayfish, Cherax quadricarinatus (Von Martens)The effect of starvation and compensatory growth on Cherax quadricarinatus were investigated for the first time. Some growth, physiology and biochemisty indexes were measured in experimental regime, including weight gain, specific growth rate, feeding rate, food-conversion efficiency, biochemical composition content, digestive enzymes activities and immune enzymes activities. Each experimental index was synthesize, and effect of starvation and compensatory growth on growth, biochemical composition, digestive and immune function in Cherax quadricarinatus were analysed. This reaearch would provide the physiological and ecological counter-measure to starvation, and provide the scientific basis for enhancing efficiency breeding for the crayfish Cherax quadricarinatus.The recovery growth experiment in Cherax quadricarinatus following different periods of starvation. The experiment lasted for18days for each test group. Group C, S2, S4and S8were deprived food for0,2,4and8days, respectively. Then each group was re-fed at satiation level for its rest experimental time.2.1At the end of starvation, the body weight of each starved group (S4and S8) was significantly lower than that of group C. At the end of experiment, the mean body weight of group S2and S4were similar to that of group C, while the body weight of group S8was still significantly lower than that of group C. Upon realimentation after periods of starvation, specific growth rate and feeding rate in terms of weight in each previously starved group were higher than those in group C. The results indicated that there was completely or partially compensatory effect in the recovery growth in Cherax quadricarinatus following starvation, and that the compensatory effect mainly resulted from significant increase of the feeding level in there covery growth. During starvation, the water and the ash content within the crayfish body increased slightly; the protein and lipid content decreased, but the losing of lipid was higher than that of protein. The results suggest lipid is the source energy mostly during starvation. At the end of the recovery growth, chemical composition in each group were similar with control group except the water content in S8test group.2.2The change of pepsion, trypsin and LPS activity in Cherax quadricarinatus was the same tend during starvation and after recovery growth, S4and S8test decrease significantly and then increase. While the activity of amylase increase a little and then decrease significantly. At the end of the recovery growth, the indexs of the digestive system of the crayfish in each group were similar with control group.2.3With time of starvation, the change of SOD, CAT, AKP and ACP activity in Cherax quadricarinatus was the same tend during starvation and after recovery growth. The tends of activity were increase a little and then decrease significantly. At the end of the recovery growth, the indexs of the immune system of the crayfish in each group were similar with control group.
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