Effects Of Different Levels Of Fly Maggot Powder And Egg Yolk Powder In Feed On The Growth,Amino Acid,Antioxidant And Immune Performance Of Larve Largemouth Bass

Largemouth bass(Micropterus salmoides)is a highly economic freshwater fish in China,however,the low survival rate of fry stage restricts the sustainable development of largemouth bass farming.Therefore,it is an effective way to improve the survival rate of the fry by exploring the special feeds for the fry of largemouth bass with suitable amino acid composition.Fly maggot meal and egg yolk meal have been used as functional protein sources in many fish feed preparations because of their rich protein content,balanced amino acid composition and antibacterial active ingredients,but little research has been reported on their application in the feeds for larve largemouth bass.In this study,we investigated the effects of different levels of fly maggot meal and egg yolk meal on the growth,body composition,amino acids,fatty acids,digestion,antioxidant and immunity of larve largemouth bass,and provided a reference for the research of special quality compound feeds for larve largemouth bass and healthy breeding.1.Effects of different levels of fly maggot meal on growth and immune performance of juvenile largemouth bassThe aim of this experiment was to investigate the effects of different additions of fly maggot meal addition to feeds on growth performance,body composition,antioxidant enzymes and immune enzyme activities of larve largemouth bass.Five diets containing different additions of fly maggot meal at 0%(H0),5%(H5),10%(H10),15%(H15)and20%(H20)were designed for the experiment.Largemouth bass fingerlings with an initial weight of 3.79±0.61 mg were divided into five groups of three parallels each,with 2000 fish in each parallel and fed in a factory recirculating water system for a period of 30 days.The results showed that the final weight,length,weight gain and specific growth rate were significantly higher in the H5 group and lower in the H20 group than in the other groups,and the survival rate was significantly lower in the H20 group than in the other groups,however,the survival rate of other groups was not affected by the amount of fly maggot powder added.The crude protein and crude ash content of the fish were not significantly affected by the different levels of fly maggot meal in the feed,while the crude fat content of the H20 group was significantly lower than that of the other groups and the moisture content was significantly higher than that of the other groups.The analysis of amino acid composition showed that the addition of 5% fly maggot meal to the feed significantly increased the content of methionine(Met)and arginine(Arg)in juvenile Largemouth bass.The addition of fly maggot powder decreased the content of total n-3 polyunsaturated fatty acids(∑n-3PUFA)and increased the content of saturated fatty acids(SFA)in the feed and fish.Compared to the H0 group,the intestinal trypsin activity of largemouth bass juveniles in the other groups was significantly higher and did not differ significantly among the groups,but no significant changes in amylase activity were observed among the groups.The results of antioxidant enzyme activities showed that the total antioxidant capacity(TAOC)and glutathione(GSH)contents were significantly higher in the H5 group than in the other groups,and the malondialdehyde(MDA)content was significantly lower than in the other groups.Meanwhile,the immunoglobulin(IGM)content in the H5 group was significantly higher than the other groups,while alkaline phosphatase(AKP)and lysozyme(LYZ)activities were enhanced with the increase of feed fly meal level,and AKP and LYZ activities in the H0 and H5 groups were significantly lower than the other groups.In conclusion,the addition of 5% fly maggot powder to the feed significantly improved the growth performance,antioxidant and immune performance of juvenile largemouth bass.2.Effects of different yolk powder levels in diets on growth and immunity of larve largemouth bassThe aim of this experiment was to investigate the effects of different types and levels of egg yolk powder in feeds on the growth performance,body composition,antioxidant enzymes and immune enzyme activities of juvenile largemouth bass.Five diets containing different yolk powder with different addition ratios and types were designed,namely 0%egg yolk powder(E0),8% homemade egg yolk powder(E8),16% homemade egg yolk powder(E16),8% commercial egg yolk powder(CE8)and 16% commercial egg yolk powder(CE16).Largemouth bass fingerlings with an initial weight of 27.18±0.49 mg were divided into 5 groups of 3 parallels each,with 280 fish in each parallel,and fed in a factory recirculating water system for 30 days.The experimental results showed that the final body weight,body length,weight gain rate and specific growth rate of E8 group were significantly higher than those of E0 group,E0 group was significantly higher than those of E16 group,and E8 and E16 groups were significantly higher than the same proportion of CE8 and CE16 groups.the survival rate of E8 group was significantly higher than those of other groups,while the feeding rate of CE16 group was significantly lower than those of the remaining groups.The crude protein,crude ash and moisture contents of the fish in each group did not differ significantly,while E16 and CE16 had the highest crude fat content,and E0 group had the lowest crude fat content.The analysis of amino acid and fatty acid composition of the juvenile fish showed that the lysine(Lys),Arg,and C20:5n-3(EPA)contents of the fish in the E8 group were significantly higher than those of the other groups.The results of antioxidant enzyme activity assay showed that among all egg yolk powder groups,only the E8 group had significantly higher GSH content,T-AOC and CAT activity than the E0 group.And the GSH content,T-AOC and CAT activities of E8 and E16 groups were significantly higher than the same ratio of CE8 and CE16 groups,while the MDA content of E8 and E16 groups was significantly lower than the same ratio of CE8 and CE16 groups.The results of immune enzyme activity and inflammatory factor gene expression measurements showed that the gene expression of lysozyme activity,complement C4,immunoglobulin content and transforming growth factor(TGF-β)were significantly higher in the E8 and E16 groups than in the same ratio of CE8 and CE16 groups,and only the E8 group was significantly higher than the E0 group.the gene expression of tumor necrosis factor(TNF-α),interleukin-1β(IL-1β)gene expressions were significantly lower than those of the same proportion of the CE8 and CE16 groups.In conclusion,the growth performance,antioxidant and immunity of the E8 and E16 groups were stronger than those of the CE8 and CE16 groups,and only the growth performance,antioxidant and immunity of the E8 group were stronger than those of the E0 group,so it is recommended to add 8%of homemade egg yolk powder.