Temporal and spatial variation of methane concentrations around lying cubicles in dairy barns

To breed cows for low methane production, farm measurement methods are required to measure individual methane production of cows. The long lying period of cows in cubicles could be utilised here. However, variable aerial conditions around cubicles may challenge this approach. The objective of this study was to (1) assess temporal and spatial variability of methane concentrations around cubicles; (2) explore influencing factors on them; and (3) assess effects of barn background variability in methane concentrations on assessed individual methane production. Concentrations around two cubicles in a naturally ventilated dairy barn were measured during a summer and a winter period. The effect of barn background variability in methane concentration on individual cow measurements was analysed in relation to the working principles of the breath methane concentration and methane flux methods. Mean methane concentrations around the cubicle were 29-37 ppm in the summer and 33-51 ppm in the winter period. Spatial variations of hourly averages of methane concentration around the cubicle were 71% in the summer and 58% in the winter period. Temporal variations of hourly averages of methane concentration varied from 115 to 153% in the summer, and from 57 to 109% in the winter period among the sample locations. These variations were mainly affected by airflows and barn management. The coefficient of variation (CV) of the background concentration strongly influenced the overall measurement CV of assessed methane production, in both the methane flux and breath methane concentration method. This information can be used to limit measurement variation in methane measurement methods.