Abstract
The effects of supplementing finishing pigs with different levels of SeY on intestinal morphology, epithelial mucus production, antioxidant activity and colonic bacterial community were evaluated. A total of thirty 90-day-old Duroc×Landrace×Yorkshire finishing pigs (with an average body weight of 54.37±2.13 kg) were randomly assigned to five treatment groups. The control group (CON) was fed a basal diet, while the other four groups were fed the basal diet supplemented with SeY at 0.3, 1, 3, and 5 mg/kg, respectively, for an 80-day of feeding trial. Intestinal morphology results showed that the addition of SeY at 0.3 mg/kg increased villus height, villus height/crypt ratio, and mucus production (as revealed by increased mucosal goblet cell number, mucus thickness, and the mRNA expression of MUC-1, claudin-1, occludin and ZO-1 gene) in the ileum compared with the control group (P<0.05), while high-dose selenium at 5 mg/kg was detrimental to the mucosal histology. Ileal antioxidant activity of SOD and GSH-Px, and jejunal mRNA expression of GPX-1 and GPX-4, were significantly higher in response to Se supplementation (P<0.05). Faecal Se excretion increased significantly in SeY supplemented groups in a dose-dependent manner (P<0.05). SeY supplementation resulted in a significant difference in beta diversity between treatment groups, as determined by Permutational Multivariate Analysis of Variance based on Bray-Curtis distance (PERMANOVA, F=2.472, P=0.002) Additionally, colonic fermentation metabolites, including acetate, propionate, butyrate, valerate, isobutyrate, and isovalerate, showed a linear decreasing trend with increasing doses of SeY (P < 0.05). Acetate, propionate, butyrate, and total short-chain fatty acids were positively correlated with the biomarker genera Agathobacter (SeY at 0.3mg/kg), while isobutyrate and isovalerate were negatively correlated with biomarker genera Lactobacillus (SeY at 0.3mg/kg) (P < 0.05). Faecalaccumulation of Se was positively correlated with the biomarker genera Alloprevotella (SeY at 3mg/kg) and Prevotellaceae_UCG-001 (SeY at 5mg/kg) and was negatively correlated with biomarker genera Agathobacter (SeY at 0.3mg/kg), Bacteroides (CON), and Faecalibacterium (CON) (P < 0.05). In conclusion, SeY doses of 0.3 mg/kg have beneficial effects on intestinal health, whereas prolonged SeY doses up to 5 mg/kg may compromise the intestinal function in finishing pigs.