Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, Center for Ruminant Nutrition and Feed Engineering Technology Research, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Laboratory of Gastrointestinal Microbiology, Jiangsu Key Laboratory of Gastrointestinal Nutrition and Animal Health, Center for Ruminant Nutrition and Feed Engineering Technology Research, College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
J Dairy Sci. 2022 Aug;105(8):6601-6615. doi: 10.3168/jds.2021-21355. Epub 2022 Jun 7.
The objective of this study was to investigate changes in the composition of mucosa-associated bacterial community, the morphology of the small intestinal epithelia, and the gene expressions of junction proteins and inflammatory cytokines in the small intestines of dairy cattle fed a high-grain (HG) diet. A total of 12 ruminally cannulated Holstein cows in mid-lactation were randomly fed either a conventional (CON) diet (40% concentrate, dry matter basis) or an HG diet (60% concentrate, dry matter basis) for 4 wk. At the end of the feeding trial, all the cows were slaughtered and then examined for changes in the small intestinal mucosa-associated bacterial communities using 16S full-length amplicon sequencing. Furthermore, the gene expression of tight junction proteins and inflammatory cytokines in the small intestinal epithelium were studied using real-time quantitative PCR. The results of nonmetric multidimensional scaling plots showed that an HG diet altered the composition of mucosa-associated bacterial communities in the jejunum and ileum. The HG feeding only increased the numbers of operational taxonomic units in the mucosa-associated bacterial community in the jejunum. At the genus level, the HG diet increased the abundance of uncultured Succinivibrionaceae and Lachnospiraceae incertae sedis in the duodenal mucosa, whereas the proportions of Veillonella and Selenomonas increased in the jejunal mucosa. Compared with the CON group, the proportions of Acetitomaculum in both the jejunal and the ileal mucosa were higher in the HG group. Analysis via PICRUSt2 (version 2.2.0-b) suggested that the HG diet increased the abundance of genes related to biodegradation of xenobiotics in the jejunal mucosa and the abundance of genes related to immune disease in the ileal mucosa. Additionally, the group fed an HG diet had higher concentrations of lipopolysaccharides in the jejunal and ileal digesta. The HG feeding caused a downregulation of the mRNA expression of occludin and ZO-1 in the jejunal epithelium, as well as of claudin-1, claudin-4, and ZO-1 in the ileal epithelium. Moreover, the HG diet caused an increase in the mRNA expression of IL-1β, IL-2, and IFN-γ in the jejunal epithelium, but a higher expression of IL-2 and IFN-γ in the ileal epithelium. Correlation analysis revealed that the alteration of lipopolysaccharide levels and mucosa-associated bacterial community might partly contribute to changes in the expression of the epithelial cytokines in the jejunum and ileum during HG feeding. These findings suggest that microbiota residing in the small intestine provide essential health benefits to host dairy cattle.
本研究旨在探究高谷物（HG）日粮饲喂奶牛后，其肠道黏膜相关菌群组成、小肠上皮形态和紧密连接蛋白及炎症细胞因子基因表达的变化。试验选用 12 头处于泌乳中期、安装有永久性瘤胃瘘管的荷斯坦奶牛，随机分为 CON 组（40%精料，干物质基础）和 HG 组（60%精料，干物质基础），每组 6 个重复，每个重复 1 头牛。预试期 14d，正试期 4 周。正试期末，所有奶牛进行屠宰，采用 16S 全长扩增子测序分析小肠黏膜相关菌群组成，采用实时定量 PCR 分析小肠上皮紧密连接蛋白及炎症细胞因子基因表达。非度量多维尺度图的结果表明，HG 日粮改变了空肠和回肠黏膜相关菌群的组成。HG 组仅增加了空肠黏膜相关菌群的操作分类单元数量。在属水平上，HG 组增加了十二指肠黏膜中未培养的 Succinivibrionaceae 和 Lachnospiraceae incertae sedis 的丰度，而空肠黏膜中 Veillonella 和 Selenomonas 的比例增加。与 CON 组相比，HG 组空肠和回肠黏膜中 Acetitomaculum 的比例均较高。PICRUSt2（版本 2.2.0-b）分析结果表明，HG 日粮增加了空肠黏膜中与异生物质生物降解相关基因的丰度，增加了回肠黏膜中与免疫性疾病相关基因的丰度。此外，HG 组空肠和回肠食糜中 LPS 浓度较高。HG 组空肠上皮中 occludin 和 ZO-1 的 mRNA 表达下调，回肠上皮中 claudin-1、claudin-4 和 ZO-1 的 mRNA 表达下调。此外，HG 组空肠上皮中 IL-1β、IL-2 和 IFN-γ 的 mRNA 表达增加，回肠上皮中 IL-2 和 IFN-γ 的表达增加。相关性分析表明，HG 日粮饲喂期间，LPS 水平和黏膜相关菌群的改变可能部分导致了空肠和回肠上皮细胞因子表达的变化。这些发现表明，肠道黏膜相关菌群为宿主奶牛提供了重要的健康益处。
