Reduction of methane emission by dairy cows
Methane emissions from dairy cows constitute more than half the global-warming impact of milk production. Methane is produced predominantly in the cow’s rumen as a result of microbial fermentation of feed components. In terms of global warming it is approximately 25 times more damaging than carbon dioxide. Reduction of methane emissions from cows will contribute substantially to reducing the ecological footprint of dairy production.
The Dutch dairy sector is aiming for a 30% reduction in greenhouse gasses by 2020, and this project contributed to that goal via a four-pronged multidisciplinary approach. First, an indicator for methane emission from individual cows was developed: this method enabled large-scale measurement of methane emissions. The methane production of individual cows in climate respiration chambers and analysed milk samples from the same cows was measured. Preliminary results indicated that about 70% of the variation in methane emissions between cows is related to differences in milk composition. Secondly, we explored the genetic variation in methane emissions between cows in order to quantify the potential of breeding measures to reduce methane emissions. Methane was also analysed in the exhaled air of cows in automatic-milking systems on commercial dairy farms. Results demonstrated that at least part of the variation in methane emissions between cows is of genetic origin. Thirdly, we characterised the composition and functioning of microorganisms in the rumen of the cow in order to quantify the effects of rumen dynamics on methane emissions. For this goal the microbial composition was analysed of rumen samples taken from the cows whose methane was measured in the climate respiration chambers. Results indicated differences in the activities of individual cow’s rumen microorganisms. Finally, we developed mechanistic models that will improve the understanding of how methane emission is influenced by the interactions between the genetics of the cow, the microorganisms in the rumen of the cow and cow feedstuffs. These interactions were also studied experimentally in more detail.