| Poor feed palatability,low feed digestion and absorption rate are common in the breeding process of Litopenaeus vannamei,which not only cause eutrophication of the water environment,but also cause frequent occurrence of shrimp diseases during the breeding process and affect economic benefits.Aquatic animal feed attractants is a kind of feed additives that increase the appetite of aquatic animals and increase the utilization rate of feed by improving the palatability of feed.In this paper,based on the screening of single and compound attractant for L.vannamei,the effects of compound feed attractant on growth performance,digestive enzyme activity and metabolism related gene expression of shrimp were studied,aiming to screen out attractants that can promote prawn feeding,accelerate prawn growth,shorten the molting cycle,improve intestinal flora and reduce secondary pollution of water bodies,and lay the foundation for green and healthy breeding of Litopenaeus vannamei.The main research contents and results are as follows:1.The twelve kinds of single formula food attractants were conducted using the feeding rate of prawn as the index,and the results showed that the effect of shannaphthalene,licorice,glucose,squid extract and fish soluble peptide was significant(P< 0.05);the compound feed attractants(CFA)were made with different proportions of shannaphthalene,licorice,ferula,cinnamon,sterol,glucose and squid extract,and the fourth group had the best attractant effect in 9 groups.2.The effects of CFA on the growth performance,digestive enzyme activity,intestinal flora composition and genes expression of related factors in hepatopancreas of Litopenaeus vannamei were studied.The results showed that the CFA could significantly improve the weight gain rate,specific growth rate and survival rate of L.vannamei,and significantly reduce the fee coefficient.0.5% CFA could significantly increase the activities of amylase and lipase in hepatopancreas of L.vannamei(P < 0.05),1% CFA could significantly increase the activities of protease,lipase and amylase in hepatopancreas and gastrointestinal tract of L.vannamei(P<0.05),and 1.5% CFA could significantly increase the activities of hepatopancreatic protease and gastrointestinal lipase(P<0.05).The relative expression of tryspsin gene in 0.5 % CFA group was significantly higher than that in control group(P<0.05),the relative expression levels of cytochrome c oxidase(COXVIc),ATP synthase(ATPase),chymotrysin BII and tryspsin genes in 1% CFA group were significantly improved(P<0.05),and the relative expression levels of tryspsin and chymotrypsin BII in the 1.5% CFA were significantly higher than those in the control group(P<0.05).The CFA can be used to improve the diversity of intestinal flora of L.vannamei.The CFA can be used to reduce the content of 3 kinds of saturated fatty acids,including pentadecanoic acid,hexadecanoic acid and octadecanoic acid in shrimp muscles and increase the content of 5kinds of unsaturated fatty acids,including cis,cis-9,12 octadecadienoic acid,cis,cis-11,14 eicosadienoic acid,all-cis-5,8,11,14 eicosatetraenoic acid,EPA and DHA.It has no effect on the types of fatty acids.Based on comprehensive considerations,it is more suitable to add 1% CFA to the feed of L.vannamei. |
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