Journal of Dairy Science - 2025

Genetic selection for feed efficiency in dairy cattle is a promising strategy tomitigate environmental emissionsreduce 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 greenhouse gas (GHG) emissions. A life cycle assessment (LCA) approach was used to quantify emissions from feed production, enteric fermentation, and manure management under three RFI selection scenarios: baseline (average genomic RFI; gRFI), 1 standard deviation (SD) improvement in gRFI heifer and gRFI cow and 3 SD improvement in gRFI heifer and gRFI cow. As expected, selection for improved gRFI led to enhanced feed conversion efficiency. Animals with a 1 SD improvement in gRFI consumed 2.73% less feed over their lifetime, while 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 CO₂ equivalent (CO₂e) emissions (35,769 vs 34,902 kg CO₂e) in the 1 SD group, and a 7.31% reduction (35,769 vs 33,153 kg CO₂e) in the 3 SD group. Enteric CH₄ 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.