Individuele methaanemissies (KB-12-006.03-002)

There is an increasing interest in mitigation of methane emission of ruminants due to the strong relation between methane emission and the greenhouse effect. Methane production currently can be reduced by feeding nutrition measures or potentially permanently reduced by genetic breeding. To apply or assess any methane mitigation methods especially those related to breeding, we first have to be capable of measuring methane production from dairy cows. Although there are already several methods to measure methane production from dairy cows, none of the methods are flawless. Methods are limited either because of technical complexity and costs or because of short sampling periods. New methods are therefore needed to measure large numbers of individual cows at farm level. The main objective of this research is to design, test, and validate existing and new methods to determine or rank the methane production of individual dairy cows at farm house level. For this purpose we first designed and constructed an artificial reference cow (ARC). We built a device that simulated exhaling and inhaling cycles and eructation of cows. Besides precisely controlling methane production at pre-set values, methane concentrations released by the ARC were controlled to fluctuate as sinusoidal cycles to mimic observed cow release patterns. We used the ARC to evaluate the breath methane concentration method that is now used in many studies. Its performance was investigated in a laboratory setup and in a barn setting with milking robot, and  we concluded that the capability of this method to adequately measure methane production is uncertain and requires further investigation into variation sources with a systematic nature. A new method was developed based on a hood sampler that measures methane fluxes from lying cows in the cubicles. A prototype of this hood sampler is now operated in a cow barn of Wageningen University.