The aim of this study was to evaluate the sulphur hexafluoride (SF6) tracer technique for methane (CH4) emission measurement in sheep. Methane emissions from ten Romney sheep were individually measured both by the SF6tracer (‘tracer CH4’) and by the indirect calorimetry chamber (‘calorimetric CH4’) techniques while fed on lucerne hay. The tracer technique involved the use of permeation tubes with pre-calibrated permeation rates (‘pre-calibrated PR’) of SF6. The ‘tracer CH4’ measurements were carried out for 5 days in digestibility crates housed within a covered yard. Sheep were transferred to calorimetry chambers for 3 days acclimatisation, followed by measurement of CH4emission for 3 days. Permeation tubes were recovered at the end of the animal trial and their ‘post-recovery PR’ determined after subsequent weighing for a 6-month period. Although the ‘tracer CH4’ was slightly lower (by 4%) and had larger variation than the ‘calorimetric CH4’ values (18.8±0.4 vs. 19.5±0.6), the two measurement techniques did not differ significantly (P>0.05) in their CH4emission estimates. The ‘post-recovery PR’ was not different (P>0.05) from their ‘pre-calibrated PR’ values, and they were highly correlated to each other (r=0.98, P<0.0001). It is concluded that the tracer technique provides a reliablealternative method for CH4measurement in forage-fed sheep.
Proceedings of the New Zealand Society of Animal Production, Volume 67, Wanaka, 431-435, 2007
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