Real-time monitoring of breath methane concentration in dairy cows using tunable diode laser spectroscopy and facemask-based sampling

Accurate measurement of enteric methane (CH 4 ) emissions from dairy cows remains challenging, as it fundamentally relies on CH 4 concentration measurements that are difficult to obtain accurately under farm conditions. Here, a facemask-based sampling system combined with tunable diode laser absorption spectroscopy (TDLAS) was developed for real-time monitoring of CH 4 concentration in exhaled breath of individual cows. The system revealed distinct dynamic CH 4 concentration patterns characterized by baseline respiration and transient peaks associated with eructation events, with concentrations reaching up to 8000 ppm by volume (ppmv). Peak concentrations were typically 4 to 10 times higher than baseline levels, with consistent minimum to maximum ratios of 0.1 to 0.3 across animals. The proposed approach provides new insights into methane release dynamics and offers potential for improved emission quantification through integration with flow measurements.