Host-Adapted Ruminal Microbiota Investigation and Functional Validation of Duolang Sheep-Derived Ligilactobacillus salivarius KS1018

This study characterized the rumen microbiota of Duolang sheep, a Xinjiang local breed, to identify potential probiotics for Hu sheep. 16S rRNA sequencing revealed that Duolang sheep possessed a distinct rumen microbial structure (beta-diversity, p < 0.05), lower diversity (higher Simpson index, p < 0.01), and a higher Firmicutes-to-Bacteroidetes ratio compared to Hu sheep. Subsequently, a Duolang-derived strain, Ligilactobacillus salivarius (L. salivarius) KS1018, was evaluated in a 56-day feeding trial with Hu sheep. Supplementation enhanced systemic immunity (serum IgG and IgM) and antioxidant status (SOD) (p < 0.05). Metabolic profiles were also modified, with serum β-hydroxybutyrate (BHB) level increasing significantly in both medium-dose (p < 0.001) and high-dose (p < 0.05) groups, whereas BUN and lipid markers (TG, CHOL) elevated significantly in the medium-dose (p < 0.05) and high-dose group (p < 0.05), respectively. The strain with medium- and high-dose also reduced fecal crude fat (p < 0.01) and influenced mucosal secretory immunoglobulin A (sIgA) by increasing levels in the duodenum while decreasing them in the rumen (p < 0.05). Ruminal histology was also altered (p < 0.01). Spearman’s correlation analysis showed that Prevotellaceae_UCG-003 was positively correlated with serum BUN (p < 0.001), IgM (p < 0.05), BHB (p < 0.01), and SOD (p < 0.01). Overall, L. salivarius KS1018 improved antioxidant capacity, systemic and mucosal immunity, and ruminal structure in Hu sheep, demonstrating its potential to influence host–microbe interactions in livestock.