Structurally distinct polysaccharides differentially affect laying performance, hepatic lipid metabolism, intestinal endocrine markers, cecal microbial and metabolic profiles in aged laying hens.

This work aimed to investigate the effects of three structurally distinct soluble polysaccharides, β-glucan, arabinoxylan (AX), and pectin (Pectin), on hepatic lipid metabolism, gut endocrine-related markers, gut microbiota and associated metabolites in laying hens during late-laying period. A total of 288 Jingfen No. 6 laying hens (63-week-old, 1,094.3 ± 8.4 g, P > 0.05) were randomly allocated to four dietary treatments, each with eight replicates and 9 hens per replicate: the basal diet (control, CON) or the CON diet supplemented with 2 g/kg of Pectin, AX, or β-glucan. One week of pre-feeding, followed by 8-week formal trial period. During weeks 1-4, Pectin and β-glucan supplementation significantly increased laying rate and egg mass (P < 0.05), whereas AX supplementation had no significant effect on these production traits. At week 8, β-glucan significantly enhanced eggshell strength, whereas AX reduced albumen height and Haugh unit (P < 0.05). Further, both polysaccharides significantly reduced hepatic triglyceride (TG) content and lipid deposition at week 4 (P < 0.05), and these effects persisted to week 8 in the β-glucan and Pectin groups. The results further revealed that Pectin and β-glucan upregulated genes related to intestinal endocrine markers including fibroblast growth factor 19 (FGF19), 5-hydroxytryptamine (5-HT), glucagon-like peptide 1 (GLP-1), and ghrelin at week 4 (P < 0.05), whereas only β-glucan maintained elevated FGF19 expression at week 8 (P < 0.01). Further, correlation analysis revealed that Faecousia abundance was positively associated with duodenal 5-HT2A expression and lipid-related metabolites sitosterol metabolite and 5-oxo-eicosatetraenoic acid, but negatively correlated with plasma TG (P < 0.05). Similarly, Ligilactobacillus showed positive associations with short-chain fatty acids (SCFA) and negative associations with hepatic TG content (P < 0.01). These findings demonstrate that dietary β-glucan and Pectin alleviate hepatic lipid accumulation, which were accompanied by remodeling the gut microbiota, enhancing intestinal endocrine-related signaling, and modulating hepatic lipid metabolism. Taken together, this work demonstrates that polysaccharides with distinct structural characteristics exert differential regulatory effects, and identifies specific polysaccharides as potential nutritional modulators for remodeling the gut microbiota and associated metabolites and alleviating hepatic lipid accumulation in aged laying hens.