This study aimed to investigate the effect of dietary slow-digestible starch (RS) on rumen microbial metabolic alterations and barrier function, and to reveal their interrelationships in lambs using native starch (NS) as the control. Twenty Hu lambs (25.1±1.1 kg) were recruited in a 56-day finishing trial and allocated into two groups offered either a corn NS (35% of dietary dry matter) or a corn RS (35% of dietary dry matter) diet. Results showed that dietary RS improved lamb weight gain and feed efficiency (P<0.05). Meanwhile, RS increased the rumen minimum pH (P<0.05) and decreased lipopolysaccharide and lactate concentrations (P<0.05). Dietary RS enhanced bacterial diversity and the abundances of Ruminococcus, while reducing the abundance of Prevotella (P<0.05). Metabolomic analysis showed that RS increased the relative concentrations of bile acids and decreased those of purines (P<0.05), leading to enriched primary bile acid biosynthesis and purine metabolism (P<0.05). Regarding rumen morphology, dietary RS increased rumen papilla length and surface area, and increased the thickness of the stratum corneum (P<0.05). Regarding gene expressions, dietary RS upregulated Claudin-1 and ZO-1, but downregulated TLR4, IL-6 and TNF-α expressions (P<0.05). Overall, dietary RS promoted rumen health by modulating microbial compositions and shifting metabolic alterations toward bile acid and purine metabolisms. Our study provides new insights into the molecular mechanisms of rumen ecosystem–host interactions in finishing lambs and highlights the potential role of RS in improving rumen health.

To Cite This Article: Tian K, Yuan H, Qiu S, Xu Z, Dicky A, Huang W, Luo G and Zhao Y, 2026. Microbial metabolic shifts and inflammation-related gene expression underlie protective effects of slow digestible starch on rumen epithelium of finishing lambs. Pak Vet J, 46(5): 1324-1332. http://dx.doi.org/10.29261/pakvetj/2026.093