KIU Publications

Feed efficiency remains a central goal in livestock production because it determines both economic viability and environmental performance. Yet conventionalmeasures such as feed conversion ratio and residual feed intake often treatefficiency as a host-level outcome and do not fully capture the biologicalprocesses that govern nutrient transformation and use. This perspective arguesthat the gastrointestinal microbiome is a critical, and still underappreciated,mediator of feed efficiency across livestock systems. In ruminants, rumen microbial communities drive the conversion of fibrous feeds into volatile fatty acids andmicrobial protein, thereby shaping host energy supply, nitrogen utilization, andmethane loss. In monogastrics, intestinal microbiota influence nutrient salvage,short-chain fatty acid production, barrier integrity, immune tone, and metabolicsignaling, with direct consequences for growth and productive performance. Wecontend that feed efficiency should be reframed as an emergent property of dietmicrobiome–host interactions rather than as a simple input–output trait. Fromthis viewpoint, microbial mediation helps explain between-animal variation innutrient bioavailability, digestive stability, inflammatory burden, and resilienceunder commercial production conditions. We further highlight how microbiomeinformed feeding strategies, including dietary bioactives, probiotics, prebiotics,enzymes, and precision nutrition approaches, could improve nutrient conversionwhile reducing methane emissions and reliance on antibiotics. Recognizing themicrobiome as a functional regulator offeed efficiency offers a more mechanisticand sustainability-oriented framework for livestock nutrition research and practice, with important implications for breeding, management, and future multiomics innovation.