Response Mechanism Of Litopenaeus Vannamei To Fish Meal Substitutes In Feed

In the present study,we replaced fish meal with biofloc meal,fish silage and fermented soybean meal in the diet of white shrimp(Litopenaeus vannamei).And we further investigated the response mechanism of shrimp to fish meal substitutes in terms of mTOR signaling pathway,intestinal microbiota,metabonomics and proteomics.All main results are as follows: 1.Evaluation of biofloc meal as an ingredient in diets for Litopenaeus vannamei under practical conditionsThis study evaluated the potential for the replacement of fish meal with biofloc meal in the diet of Litopenaeus vannamei under practical conditions.Two isonitrogenous and isolipidic diets were formulated,in which fish meal was replaced with biofloc meal at 0%(FM)and 15%(BM).A commercial diet(CD)was used as reference.A 6-week feeding trail was conducted in concrete tanks in green house with 8000 shrimps(initial weight 7.76 ± 0.61 g)per tank.Compared to FM,BM did not make negative effect on growth performance,digestive enzymes and mTOR signaling pathway(P > 0.05).The parameters for growth performance of both FM and BM were significantly higher than that of CD(P < 0.05).Through real-time quantitative PCR analysis,relative expression levels of trypsin,tor and s6 k of CD were significantly down-regulated(P < 0.05).Based on the above data,15% replacement of fishmeal with biofloc meal did not make any difference on shrimps compared with fish meal group.And mTOR signaling pathway is closed to growth of shrimp.2.Response to replacement of fish meal with fish silage of mTOR signaling pathway and intestinal microbiota in Litopenaeus vannameiThis study evaluated the potential for the replacement of fish meal with fish silage in the diet of Litopenaeus vannamei.And an Illumina-based highthroughput sequencing method was further used to analyse the intestinal microbiota of shrimp.Five isonitrogenous and isolipidic diets were formulated: a control diet(FM)containing and four experimental diets in which the fishmeal in control diet was replaced by fish silage at 25(FS25%),50(FS50%),75(FS75%)and 100%(FS100%).An 8-week feeding trail was conducted in fifteen fiberglass tanks with 50 shrimps(initial weight 0.26 ± 0.03 g)per tank.After 8 weeks trial,shrimps fed with diets FM and FS25% had significantly enhanced growth performance in terms of FW,PWG and SGR and PER(P < 0.05).No significant difference was found in body composition of all groups(P > 0.05).Through real-time quantitative PCR analysis,relative expression levels of trypsin,tor and s6 k of low replacement level groups(FM and FS25%)were significantly uo-regulated(P < 0.05).Based on the Illumina sequencing of 15 samples,family Vibrionaceae and genus Photobacterium were more abundant in high replacement level groups(50%,75% and 100%)than those in low replacement level groups(0% and 25%),which may be related to the worse growth performance of high replacement level groups.However,dietary different levels of fish silage did not make significant difference on intestinal bacterial richness,diversity and metabolism functions(P > 0.05),which indicated the limited impact of dietary fish silage on intestinal microbiota.3.Response to replacement of fish meal with fermented soybean meal of mTOR signaling pathway and intestinal microbiota in Litopenaeus vannameiThis study evaluated the potential for the replacement of fish meal with fermented soybean meal in the diet of Litopenaeus vannamei.And an Illumina-based highthroughput method was further used to analyse the intestinal microbiota of shrimp.Five isonitrogenous and isolipidicdiets were formulated: a control diet and four experimental diets in which FM in control diet was replaced by FSM at 10(FSM10%),20(FSM20%),30(FSM30%)and 40%(FSM40%).An 8-week feeding trial was conducted in fifteen fibreglass tanks with 100 shrimps(initial weight 0.27 ± 0.04 g)per tank.After 8 weeks trial,FSM20% had significantly enhanced growth performance(P < 0.05).No significant difference was found in body composition and digestive enzyme activities of all groups(P > 0.05).Through real-time quantitative PCR analysis,tor and s6 k expression levels of FSM20% were significantly up-regulated(P < 0.05).Based on the Illumina sequencing of 15 samples,dietary different levels of fermented soybean meal did not make any difference on intestinal bacterial composition,richness,diversity and metabolism functions(P > 0.05).4.Screening of signaling pathway which is sensitive to replacement of fish meal with fermented soybean meal in Litopenaeus vannamei using metabolomics and proteomics methodIn the present study,we investigated the metabolomics and proteomics of FM,FSM20% and FSM40% by LC-MS and TMT technology.Based on results of metabolomics,there were 29,97 and 61 differential metabolites in FM and FSM40%,FM and FSM20%,FSM 20% and FSM40%,respectively.These differential metabolites enriched in protein digestion and absorption,ABC transporters and central carbon metabolism in cancer signaling pathway.Based on results of proteomics,there were 202,184 and 179 differential proteins in FM and FSM40%,FM and FSM20%,FSM 20% and FSM40%,respectively.These differential proteins enriched in glucagon,lysosome and protein digestion and absorption signaling pathway.Based on results of conjoint analysis of metabolomics and proteomics,protein digestion and absorption signaling pathway changed significantly,which indicated its signicant response to replacement of fish meal with fermented soybean meal in the diet of Litopenaeus vannamei.