With demands and reliance on aquaculture still growing, there are various challenges to allow sustainable growth and the shift from fishmeal (FM) to other protein sources in aquafeed formulations is one of the most important. In this regard, interest in the use of insect meal (IM) in aquafeeds has grown rapidly. Accordingly, the aim of the present study was to assess the effects of dietary IM from Hermetia illucens (Hi) larvae included in a low-FM diet on gut microbial communities of rainbow trout (Oncorhynchus mykiss), in terms of both composition and function of microbiome. A feeding trial was conducted using 192 trout of about 100-g mean initial weight. Fish were fed in quadruplicate (4 tanks/diet) for 131 days with two diets: the control (Ctrl) contained 20% of FM as well as other protein sources, whereas the Hi diet contained 15% of Hi larvae meal to replace 50% of the FM contained in the Ctrl diet. High-throughput sequencing of 16S rRNA gene was used to identify the major feed and gut bacterial taxa, whereas Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis was performed on gut bacterial genomes to identify the major active biological pathways. The inclusion of IM led to an increase in Firmicutes, mainly represented by Bacilli class and to a drastic reduction of Proteobacteria. Beneficial genera, such as Lactobacillus and Bacillus, were enriched in the gut of fish fed with the Hi diet, whereas the number of bacteria assigned to the pathogenic Aeromonas genus was drastically reduced in the same fish group. The metagenome functional data provided evidence that dietary IM inclusion can shape the metabolic activity of trout gut microbiota. In particular, intestinal microbiome of fish fed with IM may have the capacity to improve dietary carbohydrate utilization. Therefore, H. illucens meal is a promising protein source for trout nutrition, able to modulate gut microbial community by increasing the abundance of some bacteria taxa that are likely to play a key role in fish health.

随着对水产养殖的需求和依赖仍在增长，实现可持续增长面临着各种挑战，而水产饲料配方中从鱼粉 (FM) 转向其他蛋白质来源是最重要的挑战之一。在这方面，人们对在水产饲料中使用昆虫粉 (IM) 的兴趣迅速增长。因此，本研究的目的是评估低 FM 饮食中来自Hermetia illucens (Hi) 幼虫的膳食 IM 对虹鳟 ( Oncorhynchus mykiss ) 肠道微生物群落的组成和功能的影响。微生物组。使用 192 条平均初始重量约为 100 克的鳟鱼进行喂养试验。鱼用两种饲料一式四份（4 个鱼缸/饲料）喂养 131 天：对照 (Ctrl) 含有 20% FM 以及其他蛋白质来源，而 Hi 饲料含有 15% Hi 幼虫粉，以取代 50% Ctrl 饮食中含有的 FM。 16S rRNA 基因的高通量测序用于鉴定主要的饲料和肠道细菌类群，而通过重建未观察状态进行群落系统发育研究 (PICRUSt) 分析则用于肠道细菌基因组，以确定主要的活性生物途径。 IM的加入导致厚壁菌门（主要以芽孢杆菌类为代表）的增加，以及变形菌门的急剧减少。在喂食 Hi 饮食的鱼的肠道中，乳酸菌和芽孢杆菌等有益菌属丰富，而同一鱼群中致病性气单胞菌属的细菌数量却急剧减少。宏基因组功能数据提供的证据表明，饮食中的 IM 含量可以影响鳟鱼肠道微生物群的代谢活动。 特别是，用 IM 喂养的鱼的肠道微生物组可能具有提高膳食碳水化合物利用率的能力。因此， H. illucens粉是一种很有前景的鳟鱼营养蛋白质来源，能够通过增加某些可能在鱼类健康中发挥关键作用的细菌类群的丰度来调节肠道微生物群落。