Short communication: First insights into response to selection for reducing methane emissions in dairy cows

Genetic selection against methane emissions is one of the levers to reduce the environmental impact of dairy production. Once genetic evaluation of methane emissions is available, the next step is to include this trait in breeding objectives. In this study, we investigated the consequences of three selection scenarios on methane emission and traits currently under selection for the Montbéliarde dairy cattle breed. We estimated the expected genetic progress based on genetic (co)variances between traits currently under selection and two methane traits predicted from milk mid-infrared spectra. The first scenario, representing the current total merit index, revealed the necessity of incorporating a methane trait to reduce methane emissions. The second scenario demonstrated the feasibility of achieving -1% annual methane emissions, but at the expense of a reduced genetic progress on the other selected traits, in particular milk production and fertility, which reached only 66 and 65%, respectively, of the progress achieved in the first scenario. The third scenario, maintaining 90% of the current genetic gain on existing traits while incorporating methane traits, achieved approximately -0.38% annual methane emissions. These preliminary results illustrate the feasibility of genetically reducing methane emissions through including methane traits into breeding objectives.