A Review of Enteric Methane Emission Measurement Techniques in Ruminants

SIMPLE SUMMARY: Enteric methane emissions from ruminants are a major contributor to atmospheric greenhouse gas accumulation in agricultural production systems, which may consequently contribute to climate change. Accurate measurement of methane production in ruminants is vital to develop robust national greenhouse gas emission inventories and to evaluate mitigation strategies of methane emissions. This review summarizes several common methane measurement techniques suitable for ruminant production and discusses the advantages and disadvantages of each method. There is not a perfect technique for all situations. The appropriate technique depends on the objectives and resources available. Sophisticated techniques such as respiration chambers, sulphur hexafluoride tracer and ventilated hood are usually highly accurate but labor and time intensive. Simplified techniques such as GreenFeed, sniffer method, facemask, laser methane detector and portable accumulation chamber may be less accurate but are rapid with a high throughput. In general, an understanding of measurement mechanisms and the advantages and disadvantages with an appreciation of animal behavior and welfare is necessary for all techniques. ABSTRACT: To identify relationships between animal, dietary and management factors and the resulting methane (CH(4)) emissions, and to identify potential mitigation strategies for CH(4) production, it is vital to develop reliable and accurate CH(4) measurement techniques. This review outlines various methods for measuring enteric CH(4) emissions from ruminants such as respiration chambers (RC), sulphur hexafluoride (SF(6)) tracer, GreenFeed, sniffer method, ventilated hood, facemask, laser CH(4) detector and portable accumulation chamber. The advantages and disadvantages of these techniques are discussed. In general, RC, SF(6) and ventilated hood are capable of 24 h continuous measurements for each individual animal, providing accurate reference methods used for research and inventory purposes. However, they require high labor input, animal training and are time consuming. In contrast, short-term measurement techniques (i.e., GreenFeed, sniffer method, facemask, laser CH(4) detector and portable accumulation chamber) contain additional variations in timing and frequency of measurements obtained relative to the 24 h feeding cycle. However, they are suitable for large-scale measurements under commercial conditions due to their simplicity and high throughput. Successful use of these techniques relies on optimal matching between the objectives of the studies and the mechanism of each method with consideration of animal behavior and welfare. This review can provide useful information in selecting suitable techniques for CH(4) emission measurement in ruminants.