One of the by-products of rumination – the process by which animals such as sheep and cattle digest food – is methane, a powerful greenhouse gas (GHG).
Over one year, the methane from one cow’s belches is equivalent to the CO2 emission from a small car, so there is interest in reducing this amount.
Danish workers have therefore constructed a sampling system to collect the breath of cows standing in an automatic milking machine, an activity which took place between two and 12 times per day during the research.
The two main GHG’s of interest were methane and CO2, and these were measured simultaneously using a Gasmet FTIR (Fourier Transform InfraRed) analyser. The instrument also produces spectra for the sampled gases, from which it is possible to determine the concentrations of hundreds of other gases. The supplied Calcmet software stores this spectra.
The results showed that both concentrate feed intake and total mixed ration intake were positively related to methane production, whereas milk production levels were not correlated with it. Following research of over 1000 cows, methane production was found to vary between individuals by 20% and this was shown to be a heritable trait. It is therefore possible to measure methane production rates of cattle and thereby to infer a ‘methane score’ for individual bulls. By selecting sires with a good methane score, dairy farmers could make a significant contribution to the fight against climate change. It may, however, be difficult to encourage them to make such choices unless there is significant commercial reason for doing so.