Comparative methane estimation from cattle based on total CO 2 production using different techniques

The objective of this study was to compare the precision of CH 4 estimates using calculated CO 2 (HP) by the CO 2 method (CO 2 T) and measured CO 2 in the respiration chamber (CO 2 R). The CO 2 R and CO 2 T study was conducted as a 3 × 3 Latin square design where 3 Dexter heifers were allocated to metabolic cages for 3 periods. Each period consisted of 2 weeks of adaptation followed by 1 week of measurement with the CO 2 R and CO 2 T. The average body weight of the heifer was 226 ± 11 kg (means ± SD). They were fed a total mixed ration, twice daily, with 1 of 3 supplements: wheat (W), molasses (M), or molasses mixed with sodium bicarbonate (Mbic). The dry mater intake (DMI; kg/day) was significantly greater ( P < 0.001) in the metabolic cage compared with that in the respiration chamber. The daily CH 4 (L/day) emission was strongly correlated ( r = 0.78) between CO 2 T and CO 2 R. The daily CH 4 (L/kg DMI) emission by the CO 2 T was in the same magnitude as by the CO 2 R. The measured CO 2 (L/day) production in the respiration chamber was not different ( P = 0.39) from the calculated CO 2 production using the CO 2 T. This result concludes a reasonable accuracy and precision of CH 4 estimation by the CO 2 T compared with the CO 2 R.