| Red claw crayfish(Cherax quadricarinatus)has the characteristics of fast growth,strong resistance and high yield of meat.Since its introduction from Australia,the aquaculture industry of red crayfish has developed rapidly.However,there is no special diet for red claw crayfish at any growth stage so far,and it is difficult to meet and adapt the nutritional requirements of red claw crayfish by using the commercial diet of other aquaculture animals,which restricts the development of red crayfish aquaculture.Therefore,it is urgent to develop a professional compound feed for red claw crayfish culture.Protein is one of the most important nutrient elements in animal nutrition and its cost ratio is the highest in aquatic feed.At present,fish meal is used as the main protein source in aquatic feed.However,due to limited fishing,the price of fish meal is rising,and the international influence is great.Therefore,it is necessary to find alternative raw materials for fish meal,and plant protein is one of the best alternative raw materials for fish meal.Therefore,in this study,the effects of different plant protein sources,different proportion of plant protein substitutes for fish meal and essential amino acid supplementation of plant protein formula on growth,digestion,antioxidant capacity and intestinal health of red claw crayfish during the development stage were investigated.In order to provide nutritional reference for the development of special feed for red claw crayfish in the development stage.1 Effects of four typical plant protein sources replacing dietary fish meal on growth and health of red claw crayfishIn this part of the experiment,soybean meal,rapeseed meal,peanut meal and cottonseed meal were used to replace 50% of the fish meal in the red crayfish feed,respectively,and the breeding cycle was 8 weeks.The results showed that 50%replacement of fish meal with different plant proteins had no significant effect on the survival of crayfish.The weight gain was inhibited in the peanut meal replacement group,but the replacement of other plant proteins had no significant effect on the growth of crayfish.The activities of glutathione peroxidase(GSH),alanine aminotransferase(ALT)and aspartate aminotransferase(AST)in serum were significantly increased by the intake of peanut meal replacement group,and intestinal tissue damage was caused by the intake of peanut meal replacement group.Dietary plant protein decreased the activity of digestive enzymes,but the amylase activity increased in the cottonseed meal replacement group.Moreover,cottonseed meal intake also increased the hepatopancreas alkaline phosphatase activity and muscle valine content of crayfish.Rapeseed meal intake increased the fatness of crayfish,but the intestinal perimetric membrane fell off.In conclusion,the substitution of cottonseed meal for half the fish meal in the diet of red crayfish not only has no significant effect on growth,but also can improve the digestive capacity,immune function and muscle amino acid nutritional value,so it is an appropriate substitute protein for fish meal.2 Effects of single or mixed substitution of soybean meal and cottonseed meal for feed fish meal on growth and health of red claw crayfishIn this part,the optimal replacement ratio of soybean meal and cottonseed meal to feed fish meal of red lobster was studied.75% and 100% of feed fish meal were replaced by soybean meal and cottonseed meal separately,and 50%,75% and 100% of fish meal were replaced by equal mixture of soybean meal and cottonseed meal protein content.After 8 weeks of experiment,the growth and digestive enzyme activities of shrimp were significantly decreased by replacing 100% fish meal with cottonseed meal alone or by replacing 100% fish meal with cottonseed meal mixed with soybean meal.When cottonseed meal was replaced by 100% cottonseed meal,the activities of glutathione peroxidase,alanine aminotransferase,aspartate aminotransferase and the content of malondialdehyde in the serum of crayfish were significantly increased.The arginine content in muscle of crayfish was significantly increased and the weight gain of crayfish was also increased when 50% fish meal intake was replaced by equal ratio mixture.In all treatment groups,only soybean meal and cottonseed meal were substituted for 100% fish meal alone to make the intestinal perineal membrane slightly detached from the intestinal fold.When plant protein completely replaced fish meal,the abundance of beneficial bacteria was significantly decreased,while the abundance of pathogenic bacteria was significantly increased.In addition,100% replacement of fish meal by cottonseed meal group also reduced the abundance of functional pathway of intestinal microorganism "cell movement".In conclusion,soybean meal can completely replace the feed fish meal without affecting the growth of crayfish,but cottonseed meal can only replace 75% of the fish meal.When 50% fish meal was replaced by soybean meal and cottonseed meal in equal proportion,the growth had an upward trend,and the muscle amino acid nutrition was better,which was the best substitute scheme and proportion of plant protein.3 Study on the role of essential amino acids in plant protein source feed of red claw crayfishIn this experiment,50% fish meal was replaced by a mixture of soybean meal and cottonseed meal in equal proportion without amino acid feed as the control group.Lysine or threonine diets supplemented with 0.2% and 0.4% respectively were divided into four experimental treatment groups.After 8 weeks of feeding,crayfish fed diets supplemented with 0.4% lysine or threonine showed better growth and significantly increased trypsin and glutathione peroxidase activities.The activities of alkaline phosphatase(ALP)and acid phosphatase(ACP)in hepatopancreas of crayfish in all treatment groups were higher than those in the control group,but there was no significant effect on the intestinal tissue of crayfish.In the results of intestinal microbiology analysis,the abundance and diversity of intestinal microflora decreased with 0.4% lysine supplementation,while the abundance of pathogenic bacteria increased.However,0.4% threonine increased the abundance of beneficial bacteria,and the structure of intestinal flora was more stable.In conclusion,when 50% fish meal is replaced by soybean meal and cottonseed meal,the addition of0.4% threonine can not only promote growth,but also improve antioxidant capacity and digestive capacity,and the abundance of beneficial bacteria in intestinal tract is also significantly increased. |
