Inulin enhances systemic health and egg quality by regulating gut microbiota and metabolomic profiles in laying hens

This study investigated the effects of dietary inulin supplementation on systemic health and egg quality in laying hens through changes in the gut microbiota and metabolome. A total of 288 healthy 15-week-old laying hens were randomly assigned to a basal diet (CON) or the same diet supplemented with 1.5 g/kg inulin (INU). At the peak laying age of 35 weeks, egg yolk fatty acid composition was determined, cecal microbial composition was analyzed by 16S rRNA gene amplicon sequencing, and cecal metabolites were assessed using untargeted metabolomics. Compared with the CON group, the INU group showed significantly improved laying performance, systemic health-related indicators, egg quality, serum and yolk antioxidant capacity, and yolk fatty acid composition (P < 0.05), along with a significantly lower yolk malondialdehyde concentration (P < 0.05). In addition, compared with the CON group, the INU group had a higher relative abundance of potentially beneficial microbiota, particularly Bacteroides and Faecalibacterium, and higher concentrations of acetic acid, butyric acid, and isobutyric acid (P < 0.01). Cecal metabolomic analysis further showed that, compared with the CON group, the INU group had significantly altered metabolic pathways mainly related to histidine metabolism, biotin metabolism, glycerophospholipid metabolism, and tryptophan metabolism. These results indicate that dietary inulin supplementation improved laying performance, systemic health, yolk antioxidant capacity, and egg quality in laying hens, and these beneficial effects were associated with cecal microbiota shifts, increased microbial fermentation products, altered metabolic pathways, and improved antioxidant status.