Effect of zinc supplementation on growth performance, intestinal development, and intestinal barrier function in Pekin ducks with lipopolysaccharide challenge

This study was conducted to investigate the influence of zinc (Zn) supplementation on growth performance, intestinal development and intestinal barrier function in Pekin ducks. A total of 480, one-day-old male Pekin ducks were divided into 6 groups with 8 replicates: 0 mg/kg Zn, 0 mg/kg Zn +0.5 mg/kg lipopolysaccharide (LPS), 30 mg/kg Zn, 30 mg/kg Zn +0.5 mg/kg LPS, 120 mg/kg Zn, 120 mg/kg Zn +0.5 mg/kg LPS. The duck primary intestinal epithelial cells (DIECs) were divided into 6 groups: D-Zn (Zinc deficiency, treated with 2 µmol/L zinc Chelator TPEN), A-Zn (Adequate Zinc, basal medium), H-Zn (High level of Zn, supplemented with 20 µmol/L Zn), D-Zn + 20 µg/mL LPS, A-Zn + 20 µg/mL LPS, H-Zn + 20 µg/mL LPS. The results were as follows: in vivo, with Zn supplementation of 120 mg/kg reduced LPS-induced decrease of growth performance and intestine damage (P < 0.05), and increased intestinal digestive enzyme activity of Pekin ducks (P < 0.05). In addition, Zn supplementation also attenuated LPS-induced intestinal epithelium permeability (P < 0.05), inhibited LPS-induced the expression of proinflammatory cytokines and apoptosis-related genes (P < 0.05), as well as reduced LPS-induced the intestinal stem cells mobilization of Pekin ducks (P < 0.05). In vitro, 20 µmol/L Zn inhibited LPS-induced expression of inflammatory factors and apoptosis-related genes (P < 0.05), promoted the expression of cytoprotection-related genes, and attenuated LPS-induced intestinal epithelium permeability in DIECs (P < 0.05). Mechanistically, 20 µmol/L Zn enhanced tight junction protein markers including CLDN-1, OCLD, and ZO-1 both at protein and mRNA levels (P < 0.05), and also increased the level of phosphorylation of TOR protein (P < 0.05) and activated the TOR signaling pathway. In conclusion, Zn improves growth performance, digestive enzyme activity, and intestinal barrier function of Pekin ducks. Importantly, Zn also reverses LPS-induced intestinal barrier damage via enhancing the expression of tight junction proteins and activating the TOR signaling pathway.