View source for Breath sampling during milk and feeding

Several research groups have developed methods to measure CH<sub>4</sub> concentration in breath of cows during milking and/or feeding. These are often referred to as ‘sniffer methods’ because they use devices originally designed to detect dangerous gas leaks. Air is sampled near the animal’s nostrils through a tube fixed in a feed bin and connected directly to a gas analyser. The feed bin might be in an automatic milking station (Garnsworthy et al., 2012A<ref>Garnsworthy, P.C., Craigon, J., Hernandez-Medrano, J.H. and Saunders, H. 2012A. On-farm methane measurements during milking correlate with total methane production by individual dairy cows. J. Dairy Sci. 95:3166-3180.</ref>, Garnsworthy et al., 2012B<ref>Garnsworthy, P.C., Craigon, J., Hernandez-Medrano, J.H., and Saunders, N. 2012B. Variation among individual dairy cows in methane measurements made on farm during milking. J. Dairy Sci. 95:3181–3189.</ref>; Lassen et al., 2012<ref>Lassen, J., Lovendahl, P., and Madsen, J. 2012. Accuracy of noninvasive breath methane measurements using Fourier transform infrared methods on individual cows. J. Dairy Sci. 95:890-898.</ref>; Pszczola et al., 2017<ref>Pszczola, M., Rzewuska, K., Mucha, S., and Strabel, T. 2017. Heritability of methane emissions from dairy cows over a lactation measured on commercial farms. J. Anim. Sci. 95:4813-4819. doi: 10.2527/jas2017.1842.</ref>) or in a concentrate feeding station (Negussie et al., 2017<ref>Negussie, E., Lehtinen, J., Mäntysaari, P., Bayat, A.R., Liinamo, A.E., Mäntysaari, E.A., and Lidauer, M.H. 2017. Non-invasive individual methane measurement in dairy cows. Animal 11:890-899.</ref>). Different research centres use different gas analysers (Nondispersive Infrared (NDIR), Fourier-transform infrared (FTIR) or photoacoustic infrared (PAIR)) and different sampling intervals (1, 5, 20 or 90-120 seconds). Methane concentration during a sampling visit of typically between 3 and 10 minutes may be specified as the overall mean, or the mean of eructation peaks. Some centres use CO<sub>2</sub> as a tracer gas and calculate daily CH<sub>4</sub> output according to ratio of CH<sub>4</sub> to CO<sub>2</sub> and daily CO<sub>2</sub> output predicted from performance of the cow (Madsen et al., 2010<ref>Madsen, J., Bjerg, B.S., Hvelplund, T., Weisbjerg, M.R., and Lund, P. 2010. Methane and carbon dioxide ratio in excreted air for quantification of the methane production from ruminants. Livest. Sci. 129:223-227.</ref>). Repeatability and rank correlations were higher for eructation peaks than for mean concentrations, and were higher for eructation peaks than for CH<sub>4</sub> to CO<sub>2</sub> ratio (Bell et al., 2014<ref>Bell, M.J., Saunders, N., Wilcox, R.H., Homer, E.M., Goodman, J.R., Craigon, J., Garnsworthy, P.C. 2014 Methane emissions among individual dairy cows during milking quantified by eructation peaks or ratio with carbon dioxide. J. Dairy Sci. 97:6536–6546.</ref>). However, all methods show good repeatability.