The agreement between two next-generation laser methane detectors and respiration chamber facilities in recording methane concentrations in the spent air produced by dairy cows

•The Laser Methane Detector (LDM) was tested for measuring methane from dairy cows.•The LMD was suitable to measure low methane concentrations in the air.•The LMD can detect activity differences of cows kept in a respiration chamber.•The data recorded with two LMD and two chamber facilities were in good agreement.•Its utility to measure methane emissions directly on dairy cows has to be shown. In this study, the handheld laser methane detector (LMD) was discussed as a tool for estimating the methane emissions of individual dairy cows by measuring the profiles of the exhaled air. Data obtained with the most recent generation of the device were compared with those of indirect open-circuit respiration chambers, which are commonly used to quantify methane emissions from ruminants. Data from two LaserMethane Mini-Green LMD units (Tokyo Gas Engineering Solutions) exhibited high agreement with those from four respiration chambers, two at the AgroVet-Strickhof, Eschikon, Lindau (Switzerland) and two at the Leibniz Institute for Farm Animal Biology (FBN) Dummerstorf (Germany). The results were determined using Pearson and concordance correlations and the Bland–Altman method. An inverse regression analysis was used to predict the amount of methane in the chambers from the LMD data. The two LMD units also agreed well with each other in the same respiration chamber and under farm conditions. Both the LMDs and chambers were suitable for detecting differences in mean methane concentrations in the spent air produced by dairy cows during different cow activities in the chamber (p < 0.05). Therefore, the most recent LMD model can reliably quantify the dynamics of methane concentrations in the air produced by dairy cows, although the devices were originally designed to detect gas leaks with high methane concentrations in industrial applications. Further studies are needed to investigate the utility of the current LMD technology in measuring the methane profiles directly at the animal’s nostrils to quantify methane emissions from dairy cows and other ruminants.