Modulation of the Ruminant Gastrointestinal Microbiome by Dietary Compounds: Consequences for Growth and Feed Efficiency

The ruminant gastrointestinal (GI) microbiome, often described as the “second genome,” represents a complex and dynamic ecosystem essential for nutrient digestion, energy supply, and overall animal productivity. This microbial community—comprising bacteria, archaea, fungi, and protozoa—plays a pivotal role in degrading plant polysaccharides, producing volatile fatty acids (VFAs), and synthesizing microbial protein, thereby directly influencing growth performance and feed efficiency. Dietary modulation of the rumen microbiome has emerged as a promising strategy to optimize nutrient utilization and enhance livestock sustainability. Evidence demonstrates that variations in forage-to-concentrate ratios, metabolizable energy levels, and supplementation with bioactive compounds such as isoflavones, allicin, and nitro compounds can reshape microbial populations, improve fermentation profiles, and mitigate adverse effects of high-grain diets. Beyond dietary interventions, approaches including probiotics, prebiotics, rumen microbiota transplantation, and early-life microbial modulation highlight additional avenues for improving feed conversion efficiency and average daily gain. Integrated meta-omics studies further reveal microbial taxa and functional genes associated with high-efficiency phenotypes, underscoring the interplay between host genetics and microbial ecology. Collectively, these findings emphasize that targeted modulation of the ruminant GI microbiome offers a powerful framework to enhance growth performance, reduce feed costs, and support sustainable livestock production. Future research should prioritize mechanistic insights and translational strategies to balance productivity gains with environmental resilience.

Keywords:

Ruminant gastrointestinal microbiome , Feed efficiency , Growth performance