Using Laser Methane Detector for measuring methane emissions of grazing dairy cows
Methane emissions from the agricultural sector represent 7.6% of total greenhouse gas (GHG) emissions in the European Union (EU). 90% are due to enteric fermentation in ruminants. Reducing the methane emitted by these farms is therefore a real issue. To estimate these emissions, it is essential to have tools to quantify the methane emitted. For this, several tools exist such as the Laser Methane Detector (LMD). This device is recent and its use in pasture has been little studied. The objective of our study was therefore to build a protocol for measuring the methane emitted by dairy cows on pasture, with the LMD. Secondly, this protocol was tested in a trial on grazing dairy cows by the National Institute for Agronomic Research and the Environment (INRAE). The definition of measurement parameters at the LMD took place in a pre-test phase. Then, a measurement protocol containing the measurement time as well as the distance and position of the operator from the animal was established. The position, activity and behaviour of the animal was recorded for each measurement. Application of this protocol during the trial demonstrated its reliability in pasture, on dairy cows. As a result of this study, this protocol is under test in 2022 in another trial. This could then lead to the use of this protocol on commercial farms to measure and then cut methane emissions.
GrASTech has made it possible to continue and materialize the work undertaken for 5 years on the LMD by Idele. It was notably used within the framework of the European program SmartCow. It has made it possible to offer users a clear and precise protocol to standardize measurements. Thus, consulting organizations and research structures now have a reliable, fast, easy to use and economical tool for measuring enteric methane in dairy cows.
In France, 90% of the methane emitted is coming from the enteric fermentation of ruminants, and in particular those of cattle. This gas is a powerful GHG. Thus, to limit current environmental problems, cattle farms have the challenge of reducing their CH4 emissions. The LMD is a reliable, easy-to-use tool for measuring this type of emissions. This device measures a concentration of methane in the air (in ppm*m), by absorption spectroscopy, between the LMD and the target point of the laser. Currently, several LMD measurement protocols exist for cows in buildings. Studies have also highlighted the influence of certain factors on the measurements made with this tool. These can be the climatic conditions, the time of measurement but also the behavior of the measured cow. But few studies have been adapted to grazing. This study therefore aims to define a precise measurement protocol with the LMD, on grazing dairy cows. This will measure the methane emitted at different times of the day and on cows in different activities and positions. Its ability to classify these cows, according to their ration, will also be studied during its application in an INRAE trial. This work will allow to implement solutions for cutting methane emissions and measure their impact.
Solutions to reduce enteric methane emissions from dairy cows are of four types: feed, herd management, feed additives and genetics. But to be able to reduce them, they must be measured or predicted. To predict them, the equations are based on feed or milk MIR spectra. To measure them, techniques are used in scientific research. But the main difficulty remains the direct measurement on animals on farm. The Laser Methane Detector (LMD) being a portable and easy-to-use device, it allows you to go directly to the farm to measure the methane emitted at the individual level. Work has already been carried out and has made it possible to specify an “indoor” measurement protocol (Chagunda et al., 2013; Gautier, 2021; Boré et al., 2022). The work of the GrASTech project, in conjunction with Inrae, has made it possible to specify the protocol for use on pasture on dairy cows and the effects of different feeding methods. Thus, a greater number of measurement situations becomes accessible to a diversity of feeding systems including grazing periods. This should make it possible to gain in precision on the knowledge of emissions during these periods to be able to reduce them in fine.
Now that the protocol for using the LMD has been clarified in buildings and on pasture, the objective is to continue the measurements in various production conditions: breed of cow, feeding systems, feed additives, etc. A research and development program must begin in France (2023-2026) on the question of methane and its reduction. The LMD will be used both in experimental farms for monitoring trials, in partnership with Inrae, but also in commercial farms. This work should make it possible to recognize the LMD as a technique for measuring methane in various conditions and to continue the reduction work undertaken.
