Effects of oleic acid supplementation on ileal fatty acid digestibility, intestinal barrier function, and cecal microbiota in Pekin ducks fed a high-fat diet.

This study aimed to investigate the effects of a diet supplemented with oleic acid (OA) on apparent ileal digestibility (AID) of fatty acids, intestinal barrier function, and the cecal microbiota as well as its metabolites in Pekin ducks fed a high-fat diet (HFD). A total of 240 male ducks (14 d of age) were randomly assigned to three groups: control group (Con), high-fat diet (HFD), and the HFD plus 0.50% OA (HFD_OA). The experimental duration was 28 days. Results demonstrated that HFD significantly decreased the AID of ether extract and palmitic acid (P < 0.05), whereas OA supplementation effectively restored these levels and further increased the AID of total saturated fatty acids (SFAs) (P < 0.05), which led to a decreased flow of unabsorbed SFAs at the terminal ileum. Meanwhile, OA reinforced the intestinal epithelial barrier by decreasing endotoxin concentrations in both serum and ileal mucosa (P < 0.05) and upregulating the mRNA expression of tight junction (TJ) proteins (Occludin, Claudin-1, and ZO-1) and lysozyme (LYZ), along with suppressing MLCK mRNA expression (P < 0.05). Moreover, OA intervention specifically enriched the abundance of Parabacteroides and significantly increased the concentrations of short-chain fatty acids (SCFA) (P < 0.05). Spearman correlation analysis further revealed that Parabacteroides enrichment was positively correlated with LYZ mRNA expression and SCFA production (P < 0.05) and was negatively correlated with serum endotoxin levels. These results suggest that OA enhances proximal assimilation of SFAs to reduce hindgut lipid overload, thereby ameliorating dysbiosis, suppressing endotoxin concentrations in both serum and ileal mucosa, and restoring TJs to reverse HFD-induced intestinal barrier dysfunction in Pekin ducks.