Effects Of Dietary α-starch Level On Growth,Antioxidant Capacity,Glycometabolism And Metabolome Of Largemouth Bass (Micropterus Salmoides)

Currently,there are many studies on the level of carbohydrate in feed,but the study on the carbohydrate α-starch is rarely reported.In order to investigate the physiological responses of α-starch as a carbohydrate in diet to largemouth bass(Micropterus salmoides).1.Effects of dietary α-starch content on growth performance、antioxidant capacity and glycometabolism of Largemouth bass(Micropterus salmoides)According to the previous research results,largemouth bass is better adapted to about10% carbohydrate content,the diet containing 10% α-starch was designed as low carbohydrate control group(LS group),and the diet containing 20% α-starch was designed as high carbohydrate(HS group),then the experimental diets of LS group and HS group were isonitrogenous(45%)and isolipid(15%).The largemouth bass,with an initial weight of 7.56 ± 0.02 g,was fed for 8 weeks,each group was set with three repetitions,30 fish in each repetition and the fish were fed visual satiation.After that,the growth,body composition,feed utilization,antioxidant capacity and glycometabolism of the experimental fish were used as indicators,to evaluate the effect of dietary α-starch content on largemouth bass.The HS group containing 20% α-starch was compared with the LS group containing 10% α-starch,there was no significant difference in largemouth bass survival rate between the two groups.The weight gain rate(WG)and specific growth rate(SGR)of largemouth bass in HS group containing 20% α-starch were decreased(P<0.05).However,the liver glycogen content of HS group with 20% α-starch content increased cumulatively(P<0.05);Feed conversion ratio(FCR)was significantly decreased(P<0.05),but protein efficiency ratio(PER)was increased(P<0.05);The catalase(CAT)activity and gene expression level in liver were significantly downregulated in high carbohydrate group(P<0.05),while the superoxide dismutase(SOD)activity and gene expression level in liver were not significantly affected in dietary carbohydrate group(P>0.05).Plasma aspartate aminotransferase(AST)activity was significantly increased with dietary carbohydrate level increasing(P<0.05),there were no significant differences in plasma cholesterol,triglyceride,glucose and ALT between the two groups(P>0.05)and liver malondialdehyde(MDA)content was increased(P<0.05).The gene expression levels of pyruvate kinase(PK)and phosphofructokinase(PFK)were increased(P <0.05),while the gene expression levels of hexokinase(HK)and phosphoenolpyruvate carboxylated kinase(PEPCK)were not significantly different between the two groups(P >0.05).The gene expression of glycogen synthase kinase-3 β(GSK3β)was decreased(P<0.05),and the gene expression of glycogen synthase(GS)was increased(P<0.05).These results indicate that largemouth bass fed high carbohydrate with 20% α-starch content has certain negative effects on growth and antioxidant capacity,and induces and activates glycolysis pathway,glycogen synthesis and glycogen accumulation in glycometabolism.2.Effects of dietary α-starch level on plasma and liver metabolites of largemouth bass based on metabolomeTo investigate the relationship between plasma and liver metabolites of largemouth bass with the difference of growth performance,antioxidant capacity and glycometabolism in high-carbohydrate group(HS group)containing 20% α-starch.Based on liquid-mass coupling(LC-MS/MS),plasma and liver metabolites of largemouth bass were detected.Using metabolome analysis related method,there are differences between the two groups,the plasma metabolites have 56 kinds,the most significant impact are eight metabolic pathways.There were 93 different metabolites between the two groups,and 22 metabolic pathways were most significantly affected,among which eight metabolic pathways related to amino acids were significantly affected.Thus,the results obtained by metabolome method provide significant changes in metabolites in largemouth bass under high α-starch feeding conditions,and provide theoretical basis and basis for further studies on adaptation to high carbohydrate in largemouth bass.In conclusion,the largemouth bass fed two different levels of α-starch(10% and 20%),the growth and antioxidant capacity of largemouth bass in the high carbohydrate group with 20% α-starch content were inhibited,and the glycolysis pathway,glycogen synthesis were activated and glycogen accumulation.The results of metabonomics research confirmed that the largemouth bass in 10% and 20% of α-starch,the plasma and liver metabolites between two groups showed significant difference,and partial differences metabolites were closely related and the growth,antioxidant capacity,glycogen synthesis,lipid metabolism,further studies of differential metabolites will be followed.