A Comparison of Methodologies for Measuring Methane Emissions from Ruminants

Abstract

Accurate measurement techniques are needed for determining greenhouse gas (GHG) emissions in order to improve GHG accounting estimates to IPCC Tiers 2 and 3 and enable the generation of carbon credits. Methane emissions from agriculture must be well defi ned, especially for ruminant production systems where national livestock inventories are generated. This review compares measurement techniques for determining methane production at different scales, ranging from in vitro studies to individual animal or herd measurements. Feed intake is a key driver of enteric methane production (EMP) and measurement of EMP in smallholder production systems face many challenges, including marked heterogeneity in systems and feed base, as well as strong seasonality in feed supply and quality in many areas of sub-Saharan Africa.In vitro gas production studies provide a starting point for research into mitigation strategies, which can be further examined in respiration chambers or ventilated hood systems. For making measurements under natural grazing conditions, methods include the polytunnel, sulfur hexafl uoride (SF 6 ), and open-path laser. Developing methodologies are briefl y described: these include blood methane concentration, infrared thermography, pH, and redox balance measurements, methanogen population estimations, and indwelling rumen sensors.

Response to Climate Change: Evaluation of Methane Emissions in Northern Australian Beef Cattle on a High Quality Diet Supplemented with Desmanthus Using Open-Circuit Respiration Chambers and GreenFeed Emission Monitoring Systems

“…Open-circuit respiration chambers (RCs) are considered as the ‘gold standard’ for accurately measuring CH 4 production from rumen and hindgut fermentation [ 14 , 15 , 16 , 17 ]. However, RCs are expensive to construct, technically demanding to operate and maintain, and cannot be used to measure many animals at once [ 17 ].…”

A Review of Enteric Methane Emission Measurement Techniques in Ruminants

“…Hammond et al [ 17 ] found that the GF technique didn’t detect the effects of diet and animal factors on CH 4 emissions when compared with RC and SF 6 . This is possibly due to the requirement of a bait feed supplement to encourage the animal to use the facility, which may not be consumed equally by different animals and will interact with the dietary treatments, thus introducing between-day and between-animal variation in the measurement [ 9 , 58 ]. When used for animals freely grazing on pasture, it is voluntary for the animals to be assessed which could limit the measurement timing and frequency of individual animals and unbalance the number of animals measured in different treatment groups [ 17 ].…”

“…CH 4 production is associated with many factors such as animal growth stage, production efficiency, behavior, feed intake, dietary chemical composition and animal management, etc. [ 9 ]. On the other hand, any technique affecting these factors will limit its suitability for CH 4 measurement.…”

Genetic control of methane emission, feed efficiency and metagenomics in dairy cattle

“…A number of authors have labelled breath gas concentration measures as imprecise Goopy et al, 2016; and this may be the case as seen by the lower repeatability estimates of CH4_C and CO2_C and the increased CV as compared to other phenotypes. However, the aforementioned studies often compare mass flux CH 4 production (g/day) to CH 4 breath concentrations using the coefficient of determination (R 2 ) with the expectation that a deviation of R 2 from unity (1.0) indicates imprecision.…”

“…Sniffer methane phenotypes have been dismissed off hand by many authors for the great variation (implied imprecision), inaccuracy or deviations in linear association from flux methods Goopy et al, 2016;Hammond et al, 2016;. For example, in their review Hammond et al (2016) stated '…the need for high throughput methodology, e.g.…”