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

The objective of this study was to compare the precision of CH estimates using calculated CO by the CO method (COT) and measured CO in the respiration chamber (COR). The COR and COT 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 COR and COT. 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 ( < 0.001) in the metabolic cage compared with that in the respiration chamber. The daily CH (L/day) emission was strongly correlated ( = 0.78) between COT and COR. The daily CH (L/kg DMI) emission by the COT was in the same magnitude as by the COR. The measured CO (L/day) production in the respiration chamber was not different ( = 0.39) from the calculated CO production using the COT. This result concludes a reasonable accuracy and precision of CH estimation by the COT compared with the COR.