Dietary effect of low fishmeal aquafeed on gut microbiota of olive flounder (Paralichthys olivaceus) at different growth stages (MBO3_2019_06_0239_raw data)

This study was conducted to investigate the long-term effect of a low fishmeal (FM) diet comprising plant-based protein sources (PPS) on changes of gut microbial diversity in olive flounder (Paralichthys olivaceus) over the course of life. Two experimental diets were prepared to contain 74% FM (control) or 52% FM with 22% PPS (30% FM replacement, FM30). Fish were fed one of the two experimental diets for eight months, and we collected the midgut contents to analyze the gut bacterial community by Illumina Miseq based on the metagenomic sequences in the V3-V4 regions of 16S rRNA. We found that there were nine dominant phyla, which in turn presented Proteobacteria, Firmicutes, and Actinobacteria as the three major phyla in the gut microbiota of the flounder. At genus level, the dominant genera were Delftia, Prevotella, and Chthoniobacter at the juvenile stage (below 100 g/fish); Chthoniobacter, Bacillus, and Bradyrhizobium at the grower stage (400 g/fish); Chthoniobacter, Bacillus, and Delftia at the sub-adult stage (800 g/fish); and Lactobacillus, and Prevotella at the adult stage (over 1,000 g/fish). The microbial diversity in olive flounders arched from the juvenile and sub-adult stage and reached a plateau thereafter. The fish fed the FM30 diet significantly had an increased abundance of Lactobacillus and Photobacterium and had less abundance of Prevotella and Paraprevotella than the control. However, the effect of dietary PPS was not significant on total microbial richness, indicating no negative effect as feed sources on the intestinal microbiota in olive flounder. These results indicate that the life stage of olive flounder is more important in modulating intestinal microbiota than is the diet. It could also be concluded that dietary PPS might be used as a potential fishmeal alternative without any compromising effects on microbial diversity of olive flounder for long-term feeding.

本研究旨在探究以植物蛋白源（plant-based protein sources, PPS）替代部分鱼粉（fishmeal, FM）的低鱼粉日粮，对牙鲆（Paralichthys olivaceus）全生命周期肠道微生物多样性变化的长期影响。实验设置两组日粮：一组为含74%鱼粉的对照组，另一组为含52%鱼粉与22%植物蛋白源的日粮（鱼粉替代率30%，记为FM30）。将牙鲆分别饲喂上述两种实验日粮8个月，采集其中肠内容物，基于16S rRNA的V3-V4区宏基因组序列，通过Illumina Miseq平台分析肠道细菌群落组成。
研究共鉴定出9个优势菌门，其中变形菌门（Proteobacteria）、厚壁菌门（Firmicutes）与放线菌门（Actinobacteria）为牙鲆肠道菌群的三大优势菌门。属水平上，不同生长阶段的优势菌属存在显著差异：幼鱼阶段（体质量<100g/尾）的优势菌属为戴沃斯菌属（Delftia）、普雷沃氏菌属（Prevotella）和Chthoniobacter；育成阶段（体质量400g/尾）为Chthoniobacter、芽孢杆菌属（Bacillus）和慢生根瘤菌属（Bradyrhizobium）；亚成体阶段（体质量800g/尾）为Chthoniobacter、芽孢杆菌属与戴沃斯菌属；成体阶段（体质量>1000g/尾）则为乳杆菌属（Lactobacillus）和普雷沃氏菌属。牙鲆肠道微生物多样性在幼鱼至亚成体阶段逐步升高，后续趋于平稳。与对照组相比，饲喂FM30日粮的牙鲆肠道中乳杆菌属与发光杆菌属（Photobacterium）的丰度显著升高，而普雷沃氏菌属和副普雷沃氏菌属（Paraprevotella）的丰度显著降低。但植物蛋白源日粮对肠道微生物总丰富度无显著影响，表明该替代饲料源不会对牙鲆肠道菌群产生负面影响。
本研究结果显示，相较于日粮因素，牙鲆的生长阶段对肠道菌群的调控作用更为关键。同时可得出结论：长期饲喂条件下，植物蛋白源可作为潜在的鱼粉替代源，且不会对牙鲆肠道微生物多样性产生不利影响。