Abstract
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.