Fig. 4

Relationships between predominant rumen microbial groups. a Ratio of bacterial abundance to archaeal abundance, represented by 16S rRNA gene copy number obtained using qPCR. b Ratio of Firmicutes to Bacteroidetes. c Ratio of Methanobrevibacter gottschalkii to Methanobrevibacter ruminantium. The 16S rRNA gene copy number and relative abundance were log10-transformed, and the correlation analysis was performed using the Spearman’s rank correlation (ρ = correlation coefficient)