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. 2015 Sep 2;1(3):128–134. doi: 10.1016/j.aninu.2015.08.015

Table 5.

Linear equations obtained for the CH4:CO2 ratio when using mixed models with physiological state and dietary variables.1,2

Equations AIC σexpt σres R2 Eq.
CH4:CO2 Created by potrace 1.16, written by Peter Selinger 2001-2019 0.0809 (0.00197)+0.0036 (0.00158) if Phys1 −8,664 0.0076 0.0063 0.06 3a
CH4:CO2 Created by potrace 1.16, written by Peter Selinger 2001-2019 0.0776 (0.00297)+0.0034 (0.00153) if Phys1+Inline graphic −8,679 0.0079 0.0060 0.15 3b
CH4:CO2 Created by potrace 1.16, written by Peter Selinger 2001-2019 0.0706 (0.00262)+0.0034 (0.00155) if Phys1+0.0426 (0.00685) ADF −8,692 0.0079 0.0061 0.12 3c
CH4:CO2 Created by potrace 1.16, written by Peter Selinger 2001-2019 0.0681 (0.00282)+0.0034 (0.00154) if Phys1+0.0306 (0.00465) NDF −8,695 0.0080 0.0061 0.13 3d

AIC = Akaike information criterion, ADF = acid detergent fibre, NDF = neutral detergent fibre.

1

Each predictor had a significant effect (P < 0.05 or less, Wald tests) on the relationship and the data in brackets are standard errors.

2

Physi = physiological state (i = 1 for lactating cows, i = 0 for dry cows and young cattle), FPi = forage proportion (i = 1 for FP ≤ 25%, i = 2 for 25% < FP ≤ 50%, i = 3 for 50% < FP ≤ 75% and i = 4 for FP > 75%), units for ADF and NDF are kg/kg DM, reference levels for the categorical variables correspond to Phys0 and FP1.σexpt and σres, where σ = standard deviation for the random effects (expt: experiment and res: residuals).R2 values were obtained from regression analyses, after adjusting CH4:CO2 observations for the experiment effect.