An evaluation of the face mask system based on short-term measurements compared with the sulfur hexafluoride (SF6) tracer, and respiration chamber techniques for measuring CH4 emissions

The objective of the present study was to compare the short term measurement (30 min/day for 3 days) face mask system (FM), with SF6 tracer and respiration chamber (RC) techniques for measuring CH4 emissions from crossbred (Holstein × Gyr) yearling bulls fed at three intake levels. Data were derived from 17 individuals in a completely randomized design experiment in a repeated measures scheme. Bulls were fed a diet consisting of 59.6% corn silage and 40.4% concentrate on a DM basis at three levels of DM intake (DMI) of 1.2% of BW, 1.8% of BW and ad libitum. After an adaptation period, CH4 emissions were measured first using the SF6 tracer technique, followed by the FM and RC techniques, respectively. Daily CH4 emission (g/day) from bulls differed (P < 0.007) with CH4 measurements techniques, with highest emissions measured using RC (107.9 ± 15.36), followed by FM (103.2 ± 11.86) then SF6 tracer technique (87.9 ± 10.16). The CH4 emissions adjusted for differences in DMI and BW did not differ among techniques, averaging 21.5 g/kg DMI and 0.4 g/kg BW, respectively. Total CH4 emissions (g/day) were positively correlated with DMI as measured by all three techniques (SF6r = 0.93; FM r = 0.93; RC r = 0.96). The concordance correlation coefficient (CCC) for CH4 emission (g/d) were 0.82, 0.82 and 0.74 for comparisons of SF6vs RC, FM vs RC and FM vs SF6, respectively. The day-to-day (21.3%) and animal-to-animal (13.4%) variation in CH4 yield (g/kg DMI) was greater from bulls using the FM technique, compared to SF6 (18.8% and 6.8%, respectively) and RC (12.9% and 7.5%, respectively) techniques. We conclude that the short-term FM technique generated CH4 measurements that were comparable to those estimated using SF6 and chamber techniques across a range of DMI levels. However, the FM method may have limitations in terms of assessing enteric CH4 mitigation strategies that are applied over a short duration to low numbers of animals due to higher animal-to-animal and day-to-day coefficients of variation than either the SF6 or RC techniques.