Table 1.
List of developed linear and non-linear statistical models used to predict CH4 production (MJ/day) from buffaloes, sheep, goats, and tropical cattle.
| Species | Equation: CH4 (MJ/day) | RMSE | R2 | RMSPE% |
|---|---|---|---|---|
| Sheep (96) | ||||
| Eq. 1 | = 0.208(±0.040) + 0.049(±0.0039) × GE intake (MJ/day) | 0.24 | 0.86 | 22.7 |
| Eq. 2 | = 0.550(±0.172) + 1.299(±0.126) × DM intake (kg/day) − 0.266(±0.053) × FL − 0.00093(±0.00042) × NDF (g/kg) | 0.22 | 0.92 | 22.4 |
| Eq. 3 | = −0.784(±0.269) + 0.138(±0.0084) × ME intake (MJ/day) − 0.378(±0.062) × FL + 0.00294(±0.00046) × OMDm − 1.943(±0.381) × metabolizability | 0.21 | 0.94 | 24.5 |
| Eq. 4 | = 5.699(±1.94) − [5.699(±1.94) − 0.133(±0.047)] × exp[−0.021(±0.0071) × ME intake (MJ/day)] | 0.14 | 0.91 | 20.7 |
| IPCC (93)a | = 0.065 × GE intake (MJ/day) | – | – | 23.1 |
| FAO (1)b | = [(9.75 − 0.005 × DM digestibility g/kg)/100] × GE intake (MJ/day) | – | – | 30.6 |
| Goat (95) | ||||
| Eq. 5 | = 0.242(±0.073) + 0.0511(±0.0073) × DE intake (kg/day) | 0.31 | 0.83 | 30.3 |
| Eq. 6 | = −1.042(±0.271) + 2.205(±0.395) × NDF intake (kg/day) − 2.417(±1.102) × EE intake (kg/day) + 1.456(±0.323) × NFC intake (kg/day) + 0.0208(±0.0039) × OMDm (g/kg) − 0.513(±0.137) × FL | 0.14 | 0.82 | 30.3 |
| Eq. 7 | = 0.885(±0.154) + 0.809(±0.0867) × DM intake (kg/day) − 0.397(±0.0494) × FL + 0.0198(±0.0022) × OMDm (g/kg) + 2.04(±0.234) × ADF intake (kg/day) − 8.54(±0.548) × EE intake (kg/day) | 0.24 | 0.88 | 36.3 |
| Eq. 8 | = 1.721(±0.151) × {1 − exp[−0.0721(±0.0092) × ME intake (kg/day)]} | 0.17 | 0.79 | 38.0 |
| Buffalo (2, 89) | ||||
| Eq. 9 | = 1.29(±0.576) + 0.788(±0.099) × DM intake (kg/day) | – | 0.81 | 19.4 |
| Eq. 10 | = −0.436(±0.665) + 0.678(±0.184) × DM intake (kg/day) + 0.697(±0.347) × NDF intake (kg/day) | – | 0.85 | 16.1 |
| Eq. 11 | = 21.71(±3.84) − [21.71(±3.84) − 0.732(±0.637)] − exp[−0.0485(±0.0094) × DM intake (kg/day)] | – | 0.79 | 21.2 |
| Cattle (94) | ||||
| Eq. 12 | = 9.311(±1.060) + 0.042(±0.001) × GE intake + 0.094(±0.014) × NDF − 0.381(±0.092) × EE + 0.008(±0.001) × BW + 1.621(±0.119) × MF; for lactating cattle | 2.59 | – | 15.6 |
| Eq. 13 | = 2.880(±0.200) + 0.053(±0.001) × GE intake − 0.190(±0.049) × EE; for non-lactating cattle | 1.29 | – | 14.4 |
| Eq. 14 | = 1.487(±0.318) + 0.046(±0.001) × GE intake + 0.032(±0.005) × NDF + 0.006(±0.0007) × BW; For heifer cattle | 1.23 | – | 18.6 |
| Eq. 15 | = 0.221(±0.151) + 0.048(±0.001) × GE intake + 0.005(±0.0005) × BW; for steer | 0.92 | – | 15.1 |
| Tropical cattle (98) | ||||
| Eq. 16 | = 1.29(±0.906) + 0.878(±0.125) × DM intake | 5.49 | 0.70 | 31.0 |
| Eq. 17 | = 0.910(±0.746) + 1.472(±0.154) × DM intake − 1.388(±0.451) × FL − 0.669(±0.338) × ADF intake | 4.22 | 0.84 | 22.2 |
| Eq. 18 | = 71.47(±22.14) × [1 − exp(−0.0156(±0.0051) × DM intake)] | 3.56 | 0.83 | 30.3 |
aIPCC (93) had RMSPE% of 52.4, 27.2, 18.6–30.5, and 32.5 for the database of goat, buffalo, cattle, and tropical cattle, respectively.
bFAO (1) had RMSPE% of 51.0 and 19.2–29.7% for the database of goat and cattle, respectively.
GE, gross energy; DE, digestible energy; DM, dry matter; NDF, neutral detergent fiber; FL, feeding level; ADF, acid detergent fiber; ME, metabolizable energy; EE, ether extract; NFC, non-fiber carbohydrate; OMDm, organic matter digestibility at maintenance level of feed intake; MF, milk fat (%); BW, body weight (kg); RMSE, root means square error; RMSPE, root mean square prediction error.