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Table 4 Descriptive statistics of total gas production (GP), methane (CH4) production and proportion (% CH4 on total GP) for the main sources of variation analyzed in the multivariate stepwise analysis after correction for the study effect (n = 339 observations, 30 papers)

From: Methodological factors affecting gas and methane production during in vitro rumen fermentation evaluated by meta-analysis approach

Main factors

Noa

GP, mL/g DM

CH4, mL/g DM

CH4, % on total GP

mean

s.d.b

mean

s.d.

Mean

s.d.

Pressure

 Constant

145

198

94.4

31.8

17.94

15.7

5.76

 Increasing

194

185

61.4

32.4

15.29

17.6

5.95

Incubation time, h

 24

253

178

77.9

27.6

14.20

15.6

5.59

  ≥ 48

86

227

63.1

45.3

15.63

20.2

5.60

Collection time

 Before feeding

191

174

81.5

26.3

14.58

15.1

5.47

 After feeding

148

212

65.9

39.7

15.68

19.0

5.79

Donor species

 Sheep

49

162

116.6

24.5

15.60

15.9

6.40

 Bovine

290

195

67.7

33.4

16.29

16.9

5.85

N in the buffer

 Presence

296

191

78.4

32.2

17.07

16.8

6.18

 Absence

43

190

71.0

31.5

11.52

16.7

3.82

BRF/FSc

  < 130 mL/g DM

134

172

77.6

25.0

12.74

14.7

5.54

 130-140 mL/g DM

105

217

65.4

40.8

12.00

19.2

4.08

  > 140 mL/g DM

100

187

81.5

32.5

20.17

17.0

7.02

  1. aNo = number of observations accounted in each class
  2. bs.d. = standard deviation of means
  3. cBRF/FS = ratio between buffered rumen fluid and feed sample