Table 4.
Heritability (h2) (±SE) of emission parameters (determined using respiration chambers [RC] for lambs or portable accumulation chambers for lambs and ewes) without or with covariates, genetic correlations (rg) (±SE), and efficiency (Q)1 for a single emission parameter measure to select indirectly for RC CH4 yield (g/kg DMI)
| Trait | Covariate | h 2 | r g with RC CH4 yield | Q value (%) |
|---|---|---|---|---|
| Respiration chamber, lambs | ||||
| CH4, g/d | – | 0.27 (0.04) | 0.50 (0.10) | 73 |
| BW, kg | 0.27 (0.04) | 0.50 (0.10) | 73 | |
| CO2, g/d | 0.20 (0.03) | 0.76 (0.06) | 95 | |
| CH4 + CO2, mol/d | 0.20 (0.03) | 0.78 (0.06) | 97 | |
| CH4/(CH4 + CO2), mol/mol | – | 0.18 (0.03) | 0.93 (0.02) | 105 |
| Portable accumulation chamber, lambs | ||||
| CH4, g/d | – | 0.18 (0.04) | 0.34 (0.15) | 40 |
| BW, kg | 0.15 (0.03) | 0.40 (0.15) | 43 | |
| CO2, g/d | 0.18 (0.04) | 0.51 (0.14) | 60 | |
| CH4 + CO2, mol/d | 0.18 (0.04) | 0.53 (0.14) | 61 | |
| CH4/(CH4 + CO2), mol/mol | – | 0.16 (0.03) | 0.54 (0.14) | 61 |
| Portable accumulation chamber, lambs | ||||
| CH4, g/d | – | 0.19 (0.05) | 0.29 (0.15) | 35 |
| BW, kg | 0.14 (0.04) | 0.29 (0.17) | 30 | |
| CO2, g/d | 0.19 (0.05) | 0.42 (0.15) | 49 | |
| CH4 + CO2, mol/d | 0.19 (0.05) | 0.43 (0.15) | 51 | |
| CH4/(CH4 + CO2), mol/mol | – | 0.24 (0.05) | 0.48 (0.15) | 65 |
1Q = rg (hPAC_emission trait/hRC_CH4 yield), where h is the square root of the heritability.