Regulation of rumen development in neonatal ruminants through microbial metagenomes and host transcriptomes

Table 1 Postnatal changes in active rumen bacteria, rumen morphology, and metabolites of pre-weaned calves

	Calf age			P value
	1 week	3 weeks	6 weeks	P value
Active rumen bacteria
R. flavefaciens¹	3.8 ± 1.9E08^a	1.6 ± 0.4E09^b	1.3 ± 0.5E09^b	0.03
R. albus	1.4 ± 0.5E05	6.3 ± 6.2E06	2.2 ± 1.7E07	0.34
P. ruminicola	6.4 ± 2.7E04	4.4 ± 3.0E05	7.6 ± 7.4E07	0.37
E. ruminantium	7.8 ± 3.8E05	1.5 ± 0.6E06	1.6 ± 0.6E06	0.48
Rumen papillae
Length (μm)	317.8 ± 7.6^a	413.0 ± 13.6^b	678.1 ± 41.1^c	< 0.01
Width (μm)	155.5 ± 2.7^a	224.0 ± 6.3^b	275.8 ± 9.0^c	< 0.01
Rumen fermentation parameters
Acetate²	21.1 ± 2.2^a	37.0 ± 2.8^b	50.3 ± 3.8^c	< 0.01
Propionate	10.6 ± 2.0^a	25.8 ± 4.3^b	36.3 ± 1.8^c	< 0.01
Butyrate	5.6 ± 1.8^a	11.8 ± 2.7^b	17.8 ± 2.2^b	< 0.01
Isobutyrate	0.3 ± 0.04^a	0.8 ± 0.1^b	1.3 ± 0.1^c	< 0.01
Valerate	1.0 ± 0.4^a	3.7 ± 0.7^b	5.1 ± 0.8^b	< 0.01
Isovalerate	0.3 ± 0.07^a	0.8 ± 0.1^a	1.3 ± 0.3^b	< 0.01
Total	39.6 ± 6.2^a	80.5 ± 9.0^b	113.9 ± 6.9^c	< 0.01
Acetate³	55.3 ± 2.7^a	47.0 ± 2.4^b	44.2 ± 1.9^b	0.01
Propionate	26.7 ± 1.4	31.3 ± 2.9	32.1 ± 1.4	NS
Butyrate	13.0 ± 2.0	14.4 ± 2.5	15.4 ± 1.4	NS
Isobutyrate	0.8 ± 0.1	1.0 ± 0.1	1.2 ± 0.1	NS
Valerate	2.1 ± 0.5^a	4.6 ± 0.6^b	4.5 ± 0.6^b	0.01
Isovalerate	0.8 ± 0.2	1.0 ± 0.2	1.2 ± 0.2	NS

Means with different superscript letters within a row are significantly different at P < 0.05
¹Density of active rumen bacteria (16S rRNA copy/g of rumen content)
²VFA concentration (mM/mL of rumen fluid)
³Molar proportion of VFA (%)