The measurement of methane losses from grazing animals.

A detailed description is given of the construction, operation and calibration of a system designed to measure methane emissions from sheep grazing in the field under as near natural conditions as possible. Results from four preliminary studies show that emission of methane averaged 14 g day(-1) per animal, equivalent to 5.1 kg year(-1) per animal. These rates, although lower than some estimates, confirm that methane emission from sheep forms a significant proportion of the total methane emissions currently attributed to UK agriculture.