Screening Of Amino Acid Compound Attractant And Its Effect On Yellow River Carp Fed Fish Meal Free Diet

The aim of this study was to investigate the effect of crystal amino acids on the feeding of Yellow River carp(Cyprinus carpio.var)in plant protein diet.Firstly,the maze test was used to study the effects of eight crystal amino acids on the feeding of juvenile Yellow River carp by repeated experiments,comparative experiments and difference analysis.Screening of four monomeric amino acids with predatory effect and their optimal predatory concentration.Then,four kinds of compound amino acid attractants were formed according to the best concentration of attractant,and three kinds of compound amino acid attractants with better attractant effect were selected.Finally,800 Yellow River carp with average body weight of12.81 ± 0.17 g were selected and fed with three kinds of compound amino acid attractants.The experiment was divided into 5 groups,including PC group(positive control group),NC group(negative control group),AA1,AA2 and AA3 groups.Each group had 4 replicates,40 fish in each replicate.The feeding experiment lasted for 50 days.The results are as follows:1.The results of maze test of single amino acids showed that L-histidine,L-arginine,L-glycine and L-alanine had significant effects(P<0.05),and the optimal concentrations were0.2%,0.5%,0.7% and 0.4%,respectively.2.The results of maze test of compound amino acids showed that all the four compound amino acids had significant effects on Yellow River carp(P<0.05),among which group A(0.4% alanine + 0.7% glycine + 0.5% arginine)had the best effect,followed by group C(0.4% alanine + 0.7% glycine + 0.2% histidine)and group D(0.5% arginine + 0.7% glycine +0.2% histidine).The group B(0.4% alanine + 0.5% arginine + 0.2% histidine)had a significant effect on food attraction compared with the control group,but it was not as good as the best effect of amino acids alone.3.The effect of compound amino acids on Yellow River carp fed a diet without fish meal.(1)The growth results showed that compared with NC group,the final average weight and specific growth rate of AA1 group were significantly increased(P<0.05),and those of AA2 and AA3 groups were also increased,but the difference was not significant(P>0.05).The final average weight and specific growth rate of each group were significantly lower than those of PC group(P<0.05).In terms of feed coefficient,AA1,AA2 and AA3 were lower than that of NC group,but the difference was not significant(P>0.05),and that in PC group was significantly lower than that in the control group(P<0.05).The hepatopancreatic index of PC group and each attractant group was significantly lower than that of NC group(P<0.05).(2)The results of the whole fish body composition showed that the crude protein content of PC group and AA1 group was significantly higher than that in NC group(P<0.05),and AA2 and AA3 group were higher than that in NC group(P>0.05).(3)The results of serum biochemical indexes showed that alanine aminotransferase and aspartate aminotransferase in NC group and each feeding group were significantly higher than those in PC group(P<0.05).(4)The results of immune indexes showed that the serum lysozyme levels in AA1,AA2 and AA3 groups were significantly higher than those in NC group,and significantly lower than those in PC group(P<0.05).The content of alkaline phosphatase in gill of AA2 group was significantly higher than that of NC group,and that of PC group was significantly higher than that of other groups(P<0.05).(5)The results of antioxidant indexes showed that,the catalase content of serum in AA1 group was significantly higher than that in NC group(P<0.05),and that in PC group was significantly higher than that in other groups(P<0.05);the malondialdehyde content in AA1,AA2 and AA3 groups was significantly lower than that in NC group,and higher than that in PC group(P<0.05).the SOD content of liver in AA1 group was significantly higher than that in NC group(P<0.05),and that in PC group was significantly higher than that in other groups(P<0.05);The content of MDA in AA1 group was significantly lower than that in NC group(P<0.05),and that in PC group was significantly lower than that in other groups(P<0.05).The SOD content of gill in AA1 and AA2 groups was significantly higher than that in NC group(P<0.05),and that in PC group was significantly higher than that in other groups(P<0.05).(6)The results of intestinal morphology showed that the plica height and muscle thickness of foregut in AA1 group were significantly higher than those of NC group(P<0.05),and there was no significant difference between AA1 group and PC group(P>0.05);the muscle thickness of AA2 and AA3 groups was also higher than that of NC group(P>0.05).In conclusion,0.2% L-histidine,0.5% L-arginine,0.7% L-glycine and 0.4% L-alanine had significant food attractiveness for Yellow River carp.The compound amino acid attractants composed of 0.4% alanine + 0.7% glycine + 0.5% arginine,0.4% alanine + 0.7%glycine + 0.2% histidine and 0.5% arginine + 0.7% glycine + 0.2% histidine were better than the single single amino acid attractant.Adding these three kinds of compound amino acid attractants to plant protein diet can improve the growth performance,non-specific immunity and antioxidant capacity of Yellow River carp,and also improve the intestinal health.The compound attractant composed of 0.4% alanine + 0.7% glycine + 0.5% arginine had the best application effect.