On-farm methane measurements during milking correlate with total methane production by individual dairy cows

Abstract

The objective of this study was to investigate whether measurement of methane emissions by individual dairy cows during milking could provide a useful technique for monitoring on-farm methane emissions. To quantify methane emissions from individual cows on farm, we developed a novel technique based on sampling air released by eructation during milking. Eructation frequency and methane released per eructation were used to estimate methane emission rate. For 82 cows, methane emission rate during milking increased with daily milk yield (r = 0.71), but varied between individuals with the same milk yield and fed the same diet. For 12 cows, methane emission rate recorded during milking on farm showed a linear relationship (R² = 0.79) with daily methane output by the same cows when housed subsequently in respiration chambers. For 42 cows, the methane emission rate during milking was greater on a feeding regimen designed to produce high methane emissions, and the increase compared with a control regimen was similar to that observed for cows in respiration chambers. It was concluded that, with further validation, on-farm monitoring of methane emission rate during milking could provide a low-cost reliable method to estimate daily methane output by individual dairy cows, which could be used to study variation in methane, to identify cows with low emissions, and to test outcomes of mitigation strategies.

Applicability of short-term emission measurements for on-farm quantification of enteric methane

“…Breath spot samples during supplementation Recently, measurements of methane concentration in the air around the mouth of cattle have been used to provide shortterm estimates of methane flux, with these being scaled up to estimate DMP (Chagunda et al, 2009;Lassen et al, 2010;Garnsworthy et al, 2012a). In the method of Chagunda et al (2009), a hand-held laser is used to make repeated manual measurements of (background corrected) methane concentration over 15 to 25 s in the air column out to 3 m from the nose of the cows.…”

“…Despite these numerous assumptions, a solid correlation was apparent between DMP estimated from the laser-based short-term emission and RC emission measures in dairy cows (r 5 0.7; Chagunda and Yan, 2011). Garnsworthy et al (2012a) have used an alternative approach to estimating DMP from cows, relying on short-term measurements made at milking. Their method relies on monitoring methane concentration in the feed bin, while cows are ingesting supplement during milking.…”

“…Because MERm is a measure of emission rate while cattle are eating, it is not representative of the average emission rate over the entire day. This episodic emission is probably due to both increased rumen fermentation after feeding and the more frequent eructation throughout feeding as noted by Garnsworthy et al (2012a). An equation based on 12 cows whose emissions were measured over the short term while milking (MERm), and subsequently in a prolonged respiratory chamber study, was created to convert MERm values to DMP (g/d) values.…”

“…As not all the air in the feed bin is collected (as occurs in the GreenFeed unit), there is a risk that the position of the animal's head could affect measured methane concentration, although initial tests using controlled gas release indicated that this was not the case (Garnsworthy et al, 2012a). As with the GreenFeed unit, the animal's head position is considered (indirectly) in choosing whether to accept data; small emission peaks are discarded as they may have arisen when the head was away from the feed bin when the eructation occurred.…”

“…Robinson et al (2010) identified that short-term measures of methane production were strongly correlated with DMP and can be used to obtain short-term on-farm emission data without need for an RC. This paper summarises and evaluates the use of current short-term emission measurement methods for on-farm quantification of enteric emissions from ruminants.Variation in methane production and release from ruminants over time Enteric methane production has traditionally been expressed as a daily rate, although the measurement period from which this rate is derived ranges from 13.5 h to 7 days (Wright et al, 2004;Garnsworthy et al, 2012a), with 3 days being recommended and often used for RC studies (Lines et al, 2010;Xue et al, 2011). Correlation between emission rates on consecutive days is high, the correlation (in DMP or methane yield; g/kg DM) between measures made weeks or -E-mail: roger.hegarty@une.edu.au 401 months apart is far lower, which in part reflects seasonal diet changes (Mü nger and Kreuzer, 2008), but also occurs when a uniform feed source is maintained .…”