The aim of this study was to compare metrics for quantifying enteric methane (CH4) emissions from individual cows during milking using frequent spot measurements and peak analysis methods. An infrared gas analyser was used to measure the CH4 emitted by cows, and eructation peaks were identified using a Signal Processing Toolbox provided by Matlab. CH4emissions were quantified by gas peak height, peak ampli-tude and average concentration, and were expressed in grams per day and CH4 yield (grams per kilogram of dry mat-ter intake (DMI)). Peak analysis measurements of CH4 were obtained from 36 cows during 2,474 milkings, during which cows were fed a ration containing between 39 and 70 % for-age. Spot measurements of CH4 were compared to a separate dataset of 196 chamber CH4 records from another group of 105 cows, which were fed a ration containing between 25 and 80 % forage. The results showed that the metrics of CH4 peak height and CH4 peak amplitude demonstrated simi-lar positive relationships between daily CH4 emissions and DMI (both r = 0.37), and a negative relationship between CH4yield and DMI (r = -0.43 and -0.38 respectively) as observed in the chamber measurements (r = 0.57 for daily emissions and r = -0.40 for CH4 yield). The CH4 metrics of peak height and peak amplitude were highly repeatable (ranging from 0.7 to 0.81), comparable to the high repeatability of production traits (ranging from 0.63 to 0.99) and were more repeatable than chamber CH4 measurements (0.31 for daily emissions and 0.03 for CH4 yield). This study recommends quantifying CH4 emissions from the maximum amplitude of an eructation.
Bell, M. J., Garnsworthy, P., Mallis, D., Eckard, R., Moate, P., & Yan, T. (2020). Modified approach to estimating daily methane emissions of dairy cows by measuring filtered eructations during milking. Landbauforschung, 69(1), 47-56