Effects Of Feed Protein Level,Processing Technology And Particle Size Feeding Strategy On Growth Performance,Digestive Enzyme Activity And Antioxidation Of Red Swamp Crayfish (Procambarus Clarkii)

This experiment took red swamp crayfish(Procambarus clarkii)as the research object to explore the effects of feed protein level,processing technology and particle size feeding strategy on growth performance,muscle quality,digestive enzyme activity and antioxidation of red swamp crayfish.The following are the main research contents:Experiment 1: Effects of feed protein level and processing technology on growth performance,digestibility and antioxidation of red swamp crayfish.A 13-week culture experiment was conducted with 4 protein levels(28%,30%,32% and 36%)and 2 processed feeds,namely expanded feed(EF)and hard pellet feed(PF).The results showed that: 1)protein level and processing technology had significant interaction on weight gain rate and liver / body ratio of red swamp crayfish(P < 0.05).The main effect results showed that 28% protein could significantly increase the weight gain rate and specific growth rate of red swamp crayfish.The final weight,weight gain rate and specific growth rate of EF group were significantly higher than those of PF group.2)the protein level and processing technology had interactive effects on the activities of trypsin and amylase in hepatopancreas of red swamp crayfish(P < 0.05).The main effect results showed that the activities of trypsin,amylase and intestinal trypsin in hepatopancreas were the highest at 28% protein level.The activities of trypsin,amylase and intestinal trypsin in hepatopancreas in EF group were higher than those in PF group.3)protein level and processing technology had significant interaction on the activities of MDA and alkaline phosphatase in hepatopancreas of Procambarus clarkii(P < 0.05).The main effect results showed that the total antioxidant capacity and alkaline phosphatase activity of hepatopancreas as well as serum alkaline phosphatase and acid phosphatase were the lowest at 28%protein level.The total antioxidant capacity and malondialdehyde content of hepatopancreas in PF group were significantly higher and lower than those in EF group,while alkaline phosphatase activity was significantly lower than that in EF group.4)the four models(Logistic,Gompertz,Von Bertalanffy and Brody)can well simulate the growth curve of body weight and body length of Procambarus clarkii,and the degree of fit is more than 0.97.among them,the Logistic model is the best to fit the body weight and body length,and the power function can reflect the relationship between body weight and body length.To sum up,28% protein level and puffing processing technology make red swamp crayfish have the best growth performance and digestibility,and the hard pellet feed with 28% protein level can improve the antioxidant capacity of red swamp crayfish.Experiment 2: Effects of particle size feeding strategies on growth performance,digestibility and antioxidation of red swamp crayfish under different feed processing techniques.Four different particle size combinations were fed with two kinds of feed(expanded feed and hard pellet feed).3mm diameters were fed for 60 days(ES1 and PS1),2mm diameters for 10 days and 3mm diameters for 50 days(ES2 and PS2),2mm diameters for 20 days and 3mm diameters for 40 days(ES3 and PS3),2mm diameters for 30 days and 3mm diameters for 30 days(ES1 and PS1).The initial body weight of crayfish was 7.73 ±0.05 g for 60 days.The results showed that under the expanded feed size feeding strategy,the weight gain rate and specific growth rate of red swamp crayfish increased at first and then decreased,and the maximum values appeared in ES2 group,and the feed coefficient in ES2,ES3 and ES4 groups was significantly lower than that in ES1 group.The activities of amylase and lipase in hepatopancreas were not significant,but trypsin activity increased at first and then decreased and reached the highest level in ES3 group.The SOD of hepatopancreas in ES4 group was the highest and significantly higher than that in other groups(P < 0.05),and the serum MDA was the highest in ES2 group.Under the hard pellet feed strategy,the weight gain rate and specific growth rate of red swamp crayfish were the highest in PS2 group,and the feed coefficient in PS2 group,PS3 group and PS4 group was significantly lower than that in PS1 group(P < 0.05).There was no significant effect on the activities of amylase and lipase in hepatopancreas,but trypsin was the highest in PS2 group.The activity of SOD in hepatopancreas in FS3 group was the highest,which was significantly higher than that in FS1 group.The content of MDA in hepatopancreas in PS2 group and FS4 group was significantly lower than that in PS1 group.To sum up,single particle size feed(3mm)could not meet the growth requirements of juvenile red swamp crayfish.Suitable feed size combination increased digestive enzyme activity and antioxidant capacity of red swamp crayfish,promoted growth and reduced feed coefficient.Therefore,it is suggested that the puffed feed strategy of red swamp crayfish at this stage is 2mm particle size feed for20 days and 3mm particle size feed for 40 days,and hard pellet feed for 10 days and3 mm particle size feed for 50 days.