Table 3.
Mean in vivo CH4 production, dry matter and gross energy intakes, digestibility of dry matter and gross energy, methane conversion factor and methane yield for cows and heifers.
| Variable | Cows | Stand. Dev. | 95% Conf. Intervals | Heifers | Stand. Dev. | 95% Conf. Intervals |
|---|---|---|---|---|---|---|
| Mean | Mean | |||||
| Live weight, kg | 593.4 | 50.9 | 512–674 | 338.5 | 27.8 | 294–382 |
| DMI, kg d−1 | 24.9 | 0.5 | 24–25 | 10.4 | 0.5 | 9.6–11 |
| DDM intake, kg d−1 | 18.6 | 1.1 | 16–20 | 6.5 | 0.7 | 5.3–7.5 |
| Digestibility of diet, % | 74.9 | 3.1 | 69–79 | 62.2 | 3.9 | 55–68 |
| Gross energy intake, MJ d−1 | 424 | 8.5 | 16.9–17.1 | 173.0 | 7.8 | 160–185 |
| Digestibility of gross energy, % | 76.1 | 2.7 | 71–80 | 63.8 | 4.1 | 57–70 |
| CH4 emission, L d−1 | 687 | 123 | 490–882 | 248.0 | 40.0 | 184–311 |
| CH4 emission, g d−1 | 492 | 88.3 | 351–632 | 177.6 | 28.6 | 132–223 |
| CH4, L kg−1 of DMI | 27.6 | 4.8 | 19–35 | 24.0 | 4.8 | 16–31 |
| CH4, L kg−1 DDM intake | 36.7 | 5.3 | 28–45 | 39.0 | 9.8 | 23–54 |
| CH4, g kg−1 of DMI | 19.7 | 3.4 | 14–25 | 17.1 | 3.4 | 11.7–22.6 |
| CH4, g kg−1 DDM intake | 26.3 | 3.8 | 20–32 | 27.9 | 7.0 | 16–39 |
| CH4, g kg−1 milk | 21.1 | 3.3 | 15–26 | - | - | - |
| Ym, % | 6.4 | 1.1 | 4.6–8.1 | 5.7 | 1.1 | 3.8–7.5 |
| Milk yield, kg d−1 | 23.3 | 1.8 | 20–26 | - | - | - |
DMI = Dry matter intake, DDM = digestible dry matter, Ym = methane conversion factor, energy of CH4 as a percentage of GEI; the specific energy of CHR4R is 55.65 MJ kg−1. DMI = Dry matter intake, MP = milk production, DDM = digestibility of dry matter, DOM = digestibility of organic matter, LMP = liters of milk produced, ± = standard deviation.