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.

针对奶牛饲料利用效率开展遗传选育，是缓解环境排放、降低乳品生产环境足迹的极具前景的策略。本研究评估了由STgenetics公司开发的EcoFeed指数（EcoFeed index）用于剩余采食量（residual feed intake, RFI）的遗传选育效果，将其作为提升饲料利用效率、减少温室气体（greenhouse gas, GHG）排放的技术工具。本研究采用生命周期评估（life cycle assessment, LCA）方法，量化了三种RFI选育情景下饲料生产、瘤胃发酵与粪便管理环节的排放水平：基准情景（平均基因组剩余采食量，即gRFI）、青年母牛与经产母牛gRFI提升1个标准差（standard deviation, SD）情景，以及青年母牛与经产母牛gRFI提升3个标准差情景。正如预期，提升gRFI的选育可改善饲料转化效率。gRFI提升1个标准差的奶牛终身采食量降低2.73%；gRFI提升3个标准差的奶牛终身采食量降低8.2%，且未对生产性能产生负面影响。上述饲料利用效率的提升，使1个标准差组的终身二氧化碳当量（CO2 equivalent, CO2e）排放降低2.42%（35769 kg CO2e vs 34902 kg CO2e），3个标准差组则降低7.31%（35769 kg CO2e vs 33153 kg CO2e）。瘤胃甲烷（CH4）排放是奶牛终身碳足迹的最大贡献来源，在基准情景中占总排放的38.9%，凸显了遗传选育用于甲烷减排的重要性。饲料生产与粪便管理环节分别占总排放的17.51%与32.53%。本研究结果表明，采用EcoFeed指数开展RFI遗传选育，可通过提升终身饲料利用效率、降低单位牛乳生产的采食量，显著降低牛乳生产的碳强度，为乳品行业减少温室气体排放提供了关键策略。