Fig. 1.

Establishment of rumen microbiome from birth up to the first 6 weeks of life and the development of rumen papillae. a Estimated total bacterial density (DNA-based (16S rRNA gene copy/g of sample) and RNA-based (16S rRNA copy/g of sample)) in calf rumen during the first 6 weeks of life (P = 0.02). Bars represent mean bacterial densities, and error bars represent SEM. a and b represent the mean RNA-based bacterial densities different at P < 0.05. x and y represent the mean DNA-based bacterial densities different at P < 0.05. b Composition of rumen content-associated bacteria (mean relative abundance) at the phylum level. c Functional composition of rumen content-associated bacteria at level 1 SEED hierarchy/subsystems. d Estimated total archaea density using DNA-based (16S rRNA gene copy/g of sample) and RNA-based (16S rRNA copy/g of sample) quantifications. e Rumen content-associated archaeal composition at the family level. f Rumen papillae development in calves within the first 6 weeks of life. Images are obtained through a light micrograph of rumen tissue at a magnification of × 10 objective lens (bar = 200 μm)