Alfalfa intervention alters the colonization of rumen epithelial bacteria to promote rumen development and lamb health during early life

Understanding the rumen epithelial (RE) microbial community structure and population dynamics of young ruminant during development is fundamental in promoting the establishment of a well-developed rumen for animal health and production. In this study, 10-day-old Hu lambs were fed with milk replacer (B-10), milk replacer and starter (STA) or milk replacer and starter supplemented with alfalfa (S-ALF). The RE bacteria of lambs at d10, 17, 24, 38, 45 and 66 were assessed to characterize RE bacterial colonization during early life and its response to fiber intervention. In B-10 lambs, 434 operational taxonomic units (OTUs) belonging to 57 core genera were observed in the RE. A number of the fibrolytic bacteria (Butyrivibrio and unclassified Ruminococcaceae), the pectinolytic bacterium (Treponema), the protein and fat digester (p-75-a5), the short-chain fatty acids producers ([Eubacterium], Succiniclasticum, unclassified Succinivibrionaceae, and Clostridiales), and the non-fermentive bacterium (Mogibacterium) were induced by alfalfa intervention in the S-ALF group during preweaning period, which attributed to a more mature RE bacterial community. OTUs belonging to Butyrivibrio, Succiniclasticum, Bacteroidales, Desulfovibrio, Clostridiales, and Succiniclasticum induced by alfalfa intervention were positively correlated with rumen tissue genes involved in fatty acid metabolism, barrier function, and PI3KAkt, FoxO, and calcium signaling pathways. During the postweaning period, the RE bacterial composition of STA group changed significantly, while the S-ALF group did not. Our results suggested that alfalfa induced changes in RE bacteria during preweaning period which was associated with rumen health. The findings provide guidance for improving rumen health by manipulating RE bacteria during early life.