Yeast polysaccharides modulate lipid metabolism and restore oviduct inflammatory and microbial homeostasis to support egg quality in Salmonella Pullorum-challenged hens.

Abstract

Our previous work demonstrated that yeast polysaccharides (YP) possess prebiotic and immunomodulatory activity and improve performance, immunity via modulating gut microbiota in laying hens. Building on these findings, the present study examined whether YP additionally modulate layers lipid utilization and related metabolic signatures under basal conditions and mitigates oviduct dysfunction and egg-quality deterioration during Salmonella Pullorum challenge. A total of 288 Hy-Line Brown hens (35 weeks) were fed diets containing 0, 250, 500, or 1,000 mg/kg YP for 12 weeks. Egg quality and apparent total tract digestibility were recorded, and untargeted plasma metabolomics was performed in CON and YP1000 hens. Thereafter, hens from the CON and YP1000 groups were orally inoculated with S. Pullorum or saline, generating the CON, SAL, and YP + SAL groups. Post-challenge assessments included egg quality, magnum histology, oviductal albumen antimicrobial proteins, serum and oviduct cytokines, Salmonella load and LPS levels, and oviduct microbiota composition. Under basal conditions, YP linearly increased yolk color at week 12 (ANOVA, P = 0.043; linear, P = 0.015; quadratic, P = 0.045) and enhanced ether-extract digestibility (ANOVA, P = 0.004; linear, P < 0.001; quadratic, P < 0.001). Metabolomics identified 16 differential metabolites; YP1000 elevated multiple LysoPC/LysoPE species, choline, taurine-conjugated bile acids, riboflavin, and nicotinamide, and decreased PE(38:6) (P < 0.05). Following S. Pullorum challenge, SAL hens showed reduced albumen height and Haugh unit, magnum epithelial disruption, heightened IL-1β and TNF-α responses, increased Salmonella and LPS burdens, reduced ovotransferrin and lysozyme levels, and a Proteobacteria-enriched, Lactobacillus-depleted oviduct microbiota (P < 0.05). YP supplementation mitigated these outcomes: YP + SAL hens maintained internal egg quality near control values, preserved magnum structure and antimicrobial protein secretion, increased serum IL-10 while normalizing IL-1β and TNF-α, reduced Salmonella and LPS levels, and displayed higher oviduct microbial diversity with enrichment of Lactobacillus and fewer opportunistic Proteobacteria (P < 0.05). YP not only improve lipid utilization and yolk pigmentation but also enhance the resistance of the oviduct-egg axis to S. Pullorum through coordinated modulation of host inflammation and oviduct microbial balance, offering a practical nutritional tool to support egg quality and safety in layer production.