Abstract
Background: Feed efficiency (FE) is a critical determinant of economic and environmental sustainability in dairy production. The rumen microbiome plays a pivotal role in nutrient utilization, yet its modulation as a strategy to improve FE remains underexplored. Methods: This study integrated meta-omics approaches (16S rRNA sequencing, metatranscriptomics, and metabolomics) to characterize ruminal microbial features associated with FE in 120 lactating Holstein cows. Cows were classified into high (HFE) and low (LFE) feed efficiency groups based on residual feed intake (RFI). A subset (n=40) received a probiotic blend (Lactobacillus spp. and Saccharomyces cerevisiae) for 8 weeks to assess microbiome modulation. Results: HFE cows exhibited higher alpha diversity (Shannon index: 6.8 vs. 5.9, PFibrobacter succinogenes, Ruminococcus flavefaciens) and propionate-producing pathways. Probiotic supplementation increased FE by 8.5% (PConclusions: Targeted microbiome modulation through probiotics can enhance FE in dairy cattle, with multi-omics providing mechanistic insights. These findings offer a foundation for developing microbiome-based interventions to improve dairy sustainability.