Improving feed efficiency with the EcoFeed index reduces greenhouse gas emissions in dairy cattle

Genetic selection for feed efficiency in dairy cattle is a promising strategy to mitigate environmental emissions reduce the environmental footprint of dairy production.In this study, genetic selection for residual feed intake (RFI) using the EcoFeed index developed by STgenetics was evaluated as a tool to improve feed efficiency and reduce GHG emissions.A life cycle assessment approach was used to quantify emissions from feed production, enteric fermentation, and manure management under 3 RFI selection scenarios: baseline (average genomic RFI [gRFI]), a 1-SD improvement in the genomic breeding value for RFI in heifers and cows (gRFIheifer and gRFIcow), and fa 3-SD improvement in gRFIheifer and gRFIcow.As expected, selection for improved gRFI led to enhanced feed efficiency.Animals with a 1-SD improvement in gRFI consumed 2.73% less feed over their lifetime, whereas those with a 3-SD improvement consumed 8.2% less, with no impact on productivity.These improvements in feed efficiency translated into a 2.42% reduction in lifetime CO 2 equivalent (CO 2 e) emissions (35,769 vs. 34,902 kg CO 2 e) in the 1-SD group, and a 7.31% reduction (35,769 vs. 33,153 kg CO 2 e) in the 3-SD group.Enteric CH 4 emissions were the largest contributor to the lifetime carbon footprint, accounting for 38.9% of total emissions in the baseline scenario, highlighting the importance of genetic selection for methane mitigation.Feed production and manure management accounted for 17.51% and 32.53% of total emissions, respectively.These findings suggest that genetic selection for RFI using the EcoFeed index significantly reduces the carbon intensity of milk production through improved lifetime feed efficiency and subsequently reduced feed intake per unit of milk production, establishing it as a key strategy for reducing GHG emissions the dairy sector.