Fig. 9

Full text of the overview summary. Rumen microbial species, rumen microorganisms’ function, rumen metabolites, and serum metabolites were analyzed among the four groups. The top five differentially abundant microbial species and the main differential KEGG function were demonstrated (LDA score of > 2.0 and P value of < 0.05). The rumen and serum metabolism were mainly analyzed in ACon vs. BT, A16Con vs BT and A30Con vs BT. Metabolites were selected by VIP > 1 and P < 0.05. Before transport, the most bacteria were involved in polysaccharides digestion. At day 1 after-transport, serum upregulated metabolites were mainly associated with skeletal muscle catabolism and energy metabolism. At day 4 after transport, rumen microbes were in rapid reproduction and recovered by enriched pyrimidine metabolism and purine metabolism within rumen microbial functions, and higher orotidylic acid concentration from rumen microbial metabolites at this stage. At day 16 after-transport, the energy metabolism was enhanced and ruminal contents of MCP and VFAs were highest, the energy loss induced by higher methane yields and the pathogenic bacteria together caused inflammation and oxidative stress in the A16Con cattle. At this time, the most upregulated ruminal L-ornithine produces more catabolites polyamines, which cause oxidative stress to rumen microbes and their host; the most downregulated ruminal 2',3'-cAMP provided favorable growth conditions for pathogenic bacteria; and the downregulated ruminal vitamin B6 metabolism and serum PC/LysoPC disrupt immune function and inflammation reaction. At day 30 post-transport, with the decrease of L-ornithine and the increase of protozoa, the oxidative stress is relieved, and the increase of anti-inflammatory bacteria can alleviate the body’s inflammatory reaction