Dietary supplementation of Platycodon grandiflorum polysaccharides mitigates weaning stress in piglets by modulating intestinal microbiota and improving gut health.

Platycodon grandiflorum polysaccharide (PGP) extracted from Platycodon grandiflorum, which has the advantages of anti-inflammatory, antioxidant, anti-tumor, and no side effects on the organism. This study evaluated whether dietary PGP alleviates weaning-induced intestinal dysfunction in piglets. A total of 18 newly weaned piglets (6.46±0.31 kg) were allocated to 3 treatments (n = 6/group) for a 28-day feeding trial. The control group received a basal diet, while the L-PGP and H-PGP groups were supplemented with 1 g/kg and 2 g/kg PGP, respectively. On day 28, piglets were electrically stunned and euthanized by exsanguination; spleen, liver, and colon samples were collected to assess inflammatory/antioxidant markers, barrierrelated genes, and colonic microbiota. The supplementation of PGP increased the average daily gain (p<0.05), and reduced the feed-to-gain ratio of weaned piglets. In addition, PGP reduced the expression of splenic IL-1β, IL-2, and IL-4 (p<0.05). This effect was associated with upregulated mRNA levels of the key tight junction proteins Occludin, ZO‑1, and Claudin‑1 in the colonic mucosa and tissue (p<0.05). Compared with the control group, the mRNA expression levels of PKC, Nrf2 and KEAP1 in the colonic tissue of weaned piglets were increased in the HPGP (p<0.05). More importantly, H-PGP supplementation increased the relative abundances of Bacteroidota, while decreasing the abundance of Proteobacteria. Moreover, Spearman correlation analysis revealed that short-chain fatty acid-producing commensal genera (Faecalibacterium) were negatively correlated with pro-inflammatory cytokines and signaling genes, but positively correlated with antioxidant genes (p<0.05). Conversely, the relative abundance of Escherichia-Shigella was negatively correlated with the mRNA expression of PKC, Nrf2, and Keap1 (p<0.05). PGP can alleviate the weaning stress in piglets, by modulating the colonic microbiota and enhancing systemic anti-inflammatory capacity and intestinal barrier function.