Reciprocal regulation of rumen microbiota and epithelial genes in response to small peptide supplementation for feed efficiency in beef cattle

0.6% and 0.8% of SP supplement showed the highest average daily weight gain (ADG), neutral detergent fiber (NDF) digestibility, and the lowest feed conversion ratio (FCR) among all treatments, which showed significant discrepancies compared with CON treatment (<i>P</i> < 0.05). Additionally, 0.6% of SP supplement treatment showed a significant higher content of acetate, and acetate/propionate ratio compared with 0.8% and CON treatments(<i>P</i> < 0.05). Therefore, 0.6% of SP supplement treatment was considered as the optimum supplement level and applied for further microbial and rumen epithelial gene expression analysis. SP supplement significantly increased the Alpha diversity and relative abundances of the <i>Acetitomaculum, Butyrivibrio, Pseudobutyrivibrio, Bifidobacterium,</i> and <i>Butyricicoccus</i> (<i>P</i> < 0.05), while decreased the <i>Saccharofermentans</i>, and <i>Selenomonas</i> (<i>P</i> < 0.05). Rumen epithelial results showed SP supplement up-regulated genes of <i>ATP10B, ACSF2, ADGRG6,</i> and <i>GALNT15,</i> while down-regulated genes of <i>ABCC3, GEM, PDK2,</i> and <i>ADIRF</i>. The differential expressed genes mainly enriched into the catalytic activity, pyruvate metabolism, metabolic pathways, protein digestion and absorption pathways. Conclusion. These findings demonstrate that SP supplementation enhances growth performance and rumen function and provide a viable nutritional strategy for improving feed efficiency in finishing beef cattle.