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

 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

 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

 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