Table 2.
Comparisons of methods for recording methane emission in dairy cattle.
| Alternate Methods 1 Versus Respiration Chambers | ||||||||
|---|---|---|---|---|---|---|---|---|
| Method | N Cows | N Obs | Mean S.E. | Rep S.E. | Between-Cow CV 2 | Total CV | Correlation 3 (S.E.) | CCC 4 (S.E.) |
| SF6 | 33 | 97 | 471 (14.3) | 0.44 (0.13) | 11.6 | 17.4 | 0.87 (0.08) | 0.30 (0.17) |
| Respiration Chambers | 33 | 97 | 437 (10.7) | 0.36 (0.08) | 8.4 | 14.0 | ||
| GreenFeed | 27 | 63 | 433 (8.7) | 0.64 (0.08) | 12.8 | 15.9 | 0.81 (0.10) | 0.41 (0.12) |
| Respiration Chambers | 27 | 63 | 459 (6.5) | 0.51 (0.09) | 8.1 | 11.3 | ||
| NDIR Peaks | 12 | 12 | 376 (12.1) | N/A | N/A | 11.1 | 0.89 (0.07) | 0.88 (0.10) |
| Respiration Chambers | 12 | 12 | 377 (10.7) | N/A | N/A | 9.4 | ||
| NDIR CO2 t1 | 20 | 60 | 573 (16.8) | 0.58 (0.11) | 10.1 | 13.1 | 0.72 (0.11) | 0.38 (0.21) |
| Respiration Chambers | 20 | 60 | 521 (13.7) | 0.61 (0.12) | 9.1 | 11.7 | ||
| PAIR CO2 t2 | 21 | 21 | 555 (21.3) | N/A | N/A | 11.3 | 0.80 (0.08) | 0.70 (N/A) |
| Respiration Chambers | 21 | 21 | 585 (14.1) | N/A | N/A | 17.1 | ||
| Alternate methods 1 versus Alternate methods | ||||||||
| SF6 | 48 | 144 | 405 (22.5) | N/A | N/A | 38.5 | 0.40 (0.18) | 0.34 (N/A) |
| GreenFeed | 48 | 144 | 373 (13.9) | N/A | N/A | 25.8 | ||
| LMD | 11 | 88 | 432 (24.8) | 0.21 (0.11) | 19.4 | 42.7 | 0.77 (0.23) | 0.18 (0.23) |
| GreenFeed | 11 | 88 | 423 (18.5) | 0.49 (0.12) | 11.4 | 16.8 | ||
| NDIR CO2 t1 | 27 | 63 | 586 (19.4) | 0.59 (0.13) | 13.2 | 17.2 | 0.64 (0.18) | 0.14 (0.19) |
| GreenFeed | 27 | 63 | 453 (9.8) | 0.75 (0.08) | 9.7 | 11.2 | ||
| NDIR CO2 t1 | 39 | 118 | 365 (8.3) | 0.66 (0.11) | 13.9 | 17.1 | 0.60 (0.11) | 0.18 (0.19) |
| LMD | 39 | 118 | 363 (10.3) | 0.14 (0.09) | 7.5 | 19.6 | ||
| FTIR CO2 t2 | 34 | 68 | 315 (12.3) | 0.77 (0.13) | 21.3 | 24.3 | 0.57 (0.25) | 0.20 (0.22) |
| LMD | 34 | 68 | 299 (6.1) | 0.27 (0.15) | 7.5 | 14.5 | ||
| NDIR CO2 t1 | 45 | 90 | 383 (8.7) | 0.85 (0.04) | 14.0 | 15.2 | 0.58 (0.15) | 0.14 (0.19) |
| NDIR Peaks | 45 | 90 | 393 (8.1) | 0.59 (0.09) | 10.7 | 13.9 | ||
| FTIR CO2 t1 | 43 | 103 | 392 (8.1) | 0.81 (0.05) | 14.1 | 15.3 | 0.97 (0.02) | 0.79 (0.12) |
| NDIR CO2 t1 | 43 | 103 | 382 (8.9) | 0.86 (0.04) | 12.2 | 13.6 | ||
| FTIR CO2 t1 | 45 | 90 | 392 (7.9) | 0.81 (0.05) | 12.2 | 13.6 | 0.53 (0.17) | 0.15 (0.19) |
| NDIR Peaks | 45 | 90 | 382 (8.2) | 0.60 (0.09) | 10.8 | 14.0 | ||
1 SF6 = Sulphur hexafluoride tracer gas technique, LMD = Laser methane detector; NDIR = Nondispersive Infrared; FTIR = Fourier Transform Infrared; PAIR = Photoacoustic Infrared. CO2 t1 method uses CO2 predicted from milk yield, live weight and days pregnant; CO2 t2 method uses CO2 predicted from metabolisable energy intake. 2 Coefficient of variation (%). 3 When repeated measures per cow were made the repeated measures correlation was reported, when single measures per cow were made Pearson’s correlation was reported, N/A not available, due to single measurements. 4 Lin’s concordance correlation coefficient [48].