Effects Of Feed Lysine On Growth Performance,Immunity And Antioxidant Capacity Of Cherax Quadricarinatus

Cherax quadricarinatus is a freshwater economic shrimp.Due to its delicious meat,strong disease resistance,and fast growth rate,it has high edible value and huge market potential^[1].Lysine is an essential amino acid for aquatic animals,and it is also known as"growth amino acid"due to its high demand during the growth period of shrimp and crab animals.However,because it cannot be synthesized in the body of shrimp and crab animals by its own way,it can only be obtained from feed,and is also known as the first limiting amino acid of shrimp and crab animals.Currently,the demand for lysine for crayfish,Crayfish,is unclear,which hinders the development and utilization of its standard formula feed and affects the economic benefits of aquaculture.This study was conducted to investigate the effects of different lysine levels on growth performance,antioxidant and immune abilities,and muscle amino acid composition of crayfish,and to determine the optimal concentration of lysine in the diet of crayfish,in order to provide theoretical reference for the development and application of formula feed for crayfish aquaculture.The results of this test are studied as follows:1.Effects of different lysine levels on growth performance of crayfish larvaeIn this experiment,900 healthy crayfish larvae with an initial weight of（0.45±0.32）g,healthy appendages,and sensitive activity were randomly divided into five experimental groups（A-E group）,each with three replicates,each with 60 tails.Using crystal L-lysHcl as a feed lysine source,formulated feeds with different lysine levels of equal nitrogen and equal energy were prepared,with the addition amounts of 1.3%,1.6%,1.9%,2.2%,and 2.5%,respectively.The measured values are 1.15%,1.46%,1.75%,2.05%,and 2.27%,respectively.The experiment was started after 4 weeks of pre feeding and lasted for 8 weeks.The experimental results showed that compared with other groups,lysine in group D（2.05%）significantly improved the growth performance and feed utilization of crayfish larvae(P.The above results indicate that the lysine level in feed is 1.75%-2.05%;It significantly improved the weight gain rate,specific growth rate,and feed utilization rate of crayfish larvae.2.Effects of different lysine levels on muscle amino acids and digestive capacity of crayfish larvaeThe results of dietary lysine levels on the muscle amino acid composition,digestive enzymes,and nutritional composition of crayfish larvae showed that,in addition to serine,isoleucine,phenylalanine,methionine,threonine,and arginine,other essential and non essential amino acids in the muscle amino acids of crayfish larvae showed a trend of first increasing and then decreasing with the increase of lysine addition,and group D reached the maximum value,There was a significant difference（P<0.05）.The activities of pepsin and lipase increased first and then decreased with the increase of lysine concentration,and reached the maximum value in Group D,with a significant difference（P<0.05）.The level of lysine in group D was the highest in crude protein and water content of muscle,with a significant difference（P<0.05）.The above results indicate that the digestive function of group D with 2.05%lysine addition is superior to other groups,and the EAA and TEAA contents are higher than other groups;Flavor amino acids were significantly higher than other groups.3.Effects of different lysine levels on antioxidant and immune functions of crayfish larvaeAt the end of the 56 day trial,the antioxidant and immune related indicators of liver,pancreas,and muscle,as well as blood physiological and biochemical indicators were measured.The results showed that the activities of superoxide dismutase（SOD）and reducing glutathione（GSH-Px）in group C reached the maximum at the lysine level in the hepatopancreas and muscle,with significant differences（P<0.05）.The activity of catalase（CAT）in the liver and pancreas of group C reached the maximum,with a significant difference（P<0.05）.The muscle CAT activity in group D reached the maximum value,significantly higher than that in other groups（P<0.05）.The gene expression level of SOD in liver and pancreas of group C was significantly higher than that of other groups（P<0.05）,and the gene expression level of SOD in muscle of group D was significantly higher than that of other groups（P<0.05）.The reductive glutathione（GPx）levels in hepatopancreas and muscle tissue in groups D and E were significantly higher than those in other groups（P<0.05）.The activities of lysozyme（LZM）,acid phosphatase（AKP）,and alkaline phosphatase（ACP）in group D were significantly higher than those in other groups(P.The gene expression levels of anti lipopolysaccharide factor（ALF）,lysozyme（LZM）,chitosan hyperglycemic hormone（CHH）,and serine protease inhibitor（SPI）in muscle and hepatopancreatic tissues of group D were significantly higher than those of other groups（P<0.05）.The activities of albumin（ALB）,globulin（GLB）,and ceruloplasmin（HEM）in group D were significantly higher than those in other groups（P<0.05）,while the activities of ALT and AST were significantly lower than those in other groups（P<0.05）.The above results indicate that young red crayfish with lysine levels of 1.75%（Group C）and 2.05%（Group D）have stronger antioxidant,immune,and blood biochemical indicators.In Abstract:In this study,the optimal amount of lysine added to the formula feed for crayfish larvae is 2.05%.