Abstract

The objective of the current study was to determine the precision of CH4 emission estimates from simulated spot-samples of variable time length (0.25 to 3.0 h) and over time compared to 24-h measured CH4 emissions, both based on respiration chamber data of the same day within cattle. Respiration chamber methane data, recorded approximately every 3 min, from two experiments were used, each with 12 growing beef cattle measured over two or three consecutive days. The ~3 min CH4 emissions during 24 h per animal per day were averaged in time intervals (bins; i.e. simulated spot-sample duration) of 0.25, 0.5, 1.0 and 3.0 h (expressed as g/d) from morning and from afternoon feeding. Precision of each time bin was evaluated by determining between-animal coefficient of variation (CV) and Pearson correlation (r) with 24-h measured emissions. In general, the average CV increased and the CV became more variable over time when the bin duration decreased from 3 h to 0.25 h. The correlation was low (r of approximately 0.1 to 0.5) in the first 0.5 to 2 h after the start of a feeding, after which the correlations increased (r of approximately 0.5 to 0.9) and remained relatively constant up to about 8 h after feeding. The overall trends observed suggest that the precision of a CH4 measurement improved with increasing simulated spot-sample (bin) duration from 0.25 to 3 h and the best time to take a spot-sample (based on any of the bin durations) would be between approximately 1 to 6-8 h after feeding. However, the best timing to perform spot-sampling was not fully consistent between the experiments and between emissions after morning and afternoon feeding, which warrants further investigation. Keywords: Spot-sampling; enteric methane; precision; time bin; variation

AA, Biswas, and A Joner

New Zealand Journal of Animal Science and Production, Volume 80, Online, 65-69, 2020