3.1 Species diversity analysis
Fresh faecal samples were obtained from the cattle of CON group and 3 treatment groups after 105 days of the treatment to investigate the effect of adding 3%, 6%, 9% Scutellaria baicalensis Georgi stems and leaves on cattle intestinal microbiota composition. A total of 113,457 labels were matched with 19 samples, with effective-quality control rate of 89.30% and high-quality control rate of 85.96% (Table 3). The rarefaction curve (average curve for each group) indicates that most microbial diversity has been fully recorded (Figure 1A). According to the Wilcoxon rank-sum test, no significant differences were observed in Chao, Observed species, Shannon, Simpson, Faith, Pielou or Goods coverage (Figure 1B) between the treatment group and the CON group (P > 0.05). However, some substantial differences in 3 treatment groups and CON group were observed due to adding Scutellaria baicalensis Georgi stems and leaves. The NMDS ranking diagram, based on Bray Curtis distance measurement, demonstrated that the faecal bacterial population in the sample was separated by adding Scutellaria baicalensis Georgi stems and leaves (Figure 1C). According to Anosim analysis, the differences between groups are shown in Table 4. There was a significant difference between the CON group and the group with adding 9% Scutellaria baicalensis Georgi stems and leaves (P < 0.05), as well as the group with adding 3% Scutellaria baicalensis Georgi stems and leaves and the 9% group (P < 0.05).
3.2 Differential microbiota expression
Analyzing the classification components with relative abundance greater than 1% can determine the bacterial population induced by adding Scutellaria baicaliasis stems and leaves (Figure 2A). Firmicutes were the most abundant in CON group, with an average abundance of 49.47%, followed by Bacteriodota (32.81%). In the group of adding 3% Scutellaria baicalensis Georgi stems and leaves, Firmicutes (50.85%) also occupied an absolute advantage, followed by Bacteriodota (31.47%), Spirochaetes (8.57%), Tenericutes (4.08%), Verrucomicrobia (1.88%) and Proteobacteria (1,39%). In the group of adding 6% Scutellaria baicalensis Georgi stems and leaves, Firmicutes (46.62%) also occupied an absolute advantage, followed by Bacteriodota (35.57%), Spirochaetes (8.09%), Tenericutes (4.92%), Verrucomicrobia (1.43%) and Proteobacteria (1.23%). In the group of adding 9% Scutellaria baicalensis Georgi stems and leaves, Firmicutes (48.06%) also occupied an absolute advantage, followed by Bacteriodota (35.67%), Spirochaetes (8.90%), Tenericutes (4.76%), Verrucomicrobia (0.62%) and Proteobacteria (0.84%). To investigate the evolutionary relationships of species at the genus level, sample sequences from the Top 100 genera were acquired through multiple sequence alignment, as shown in Figure 2B. 20% can be annotated to the genus level. Treponema was the most abundant in CON group, with an average abundance of 9.19%, followed by 5-7N15 (4.13%). In the group of adding 3% Scutellaria baicalensis Georgi stems and leaves, Treponema (8.42%) also occupied an absolute advantage, followed by 5-7N15 (3.46%), Clostridiaceae_Clostridium (2.31%) and CF231 (1.9%). In the group of adding 6% Scutellaria baicalensis Georgi stems and leaves, Treponema (7.59%) also occupied an absolute advantage, followed by 5-7N15 (4.62%), Clostridiaceae_Clostridium (1.30%) and CF231 (1.58%). In the group of adding 9% Scutellaria baicalensis Georgi stems and leaves, Treponema (8.36%) also occupied an absolute advantage, followed by 5-7N15 (4.34%), Clostridiaceae_Clostridium (1.82%) and CF231 (1.62%). In addition, we have mapped the taxonomic hierarchy (Figure 2C) and evolutionary tree diagrams (Figure 2D) for the phylum, class, order, family, and genus with the highest abundance of 50 OTUs.
Wayne diagrams and species composition heatmaps were drawn to further compare the differences in species composition between samples. The Wayne diagram is shown in Figure 3A, with 1111 identical OTUs in the four groups. There are 101, 146, 138, and 121 OTUs in CON group, and adding 3%, 6%, and 9% Scutellaria baicalensis Georgi stems and leaves groups, respectively. Draw a heat map of the top 20 OTUs with average abundance as shown in Figure 3B. Description of OTU_131, OTU_56, OTU_808, OTU_2509, OTU_1424, OTU_83, OTU_93, OTU_2944, OTU_1792, OTU_776, OTU_2839, OTU_166, OTU_1178, OTU_167, OTU_814, OTU_2325, OTU_269, OTU_262, OTU_162 and OTU_957 is an important indicator of inter group differences.
3.3 Enrichment of differential microbiota pathways
These bacteria were subjected to a KEGG, MetaCyc and COG analysis, which revealed substantial differences (Figure 4A). Differential microorganisms were found to be mainly involved in the Nucleoside and Nucleotide Biosynthesis, Amino Acid Biosvnthesis, Cofactor, Prosthetic Group, Electron Carrier, and Vitamin Biosynthesis, Fatty Acid and Lipid Biosynthesis, Carbohydrate Biosynthesis, Carbohydrate Degradation, Carboxylate Degradation, Nucleoside and Nucleotide Degradation, C1 Compound Utilization and Assimilation, Polymeric Compound Degradation, Fermentation, Glycolysis, TCA cycle, Glycan Biosynthesis and Glycan Degradation pathway through pathway enrichment. In addition, the PIZI graph shows that the five most abundant phylum species are Firmicutes, Bacteroidetes, Spirochetes, Tenericulates and Verrucomimicrobia (Figure 4B).