Synbiotics improves growth performance and nutrient digestibility, inhibits PEDV infection and prevents intestinal barrier dysfunction by mediating innate antivirus immune response in weaned piglets challenged with PEDV.

This experiment was conducted to explore the effects of dietary synbiotics supplementation on growth performance, immune function, and intestinal barrier function in piglets challenged with PEDV. Forty crossbred (Duroc × Landrace × Yorkshire) weaned piglets (26 ± 1 day-old) with a mean body weight of 6.62 ± 0.36 kg were randomly allotted to five groups: Control (CON) I and CONII group, both fed basal diet; 0.1% synbiotics (SYB) group, 0.2% SYB group and 0.2% yeast culture (YC) group, fed basal diet supplemented with 0.1%, 0.2% synbiotics, and 0.2% yeast culture, respectively. On d 22, all piglets were orally administrated with 40 mL PEDV (5.6 × 103 TCID50/mL) except piglets in CONI group, which were administrated with the same volume of sterile saline. The trial lasted for 26 days. Before PEDV challenge, dietary 0.1% synbiotics supplementation increased final body weight, average daily gain (ADG) and decreased the ratio of feed to gain (F/G) during 0-21d (P < 0.05), as well as improved the apparent nutrient digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), and gross energy (GE). At the same time, 0.2% YC also improved the apparent nutrient digestibility of DM, OM, EE and GE (P < 0.05). PEDV challenge increased diarrhea rate and diarrhea indexes while decreased ADG (P < 0.05) from 22-26 d, and induced systemic and intestinal mucosa innate immune and pro-inflammatory responses, destroyed intestinal barrier integrity. The decrease in ADFI and ADG induced by PEDV-challenge was suppressed by dietary synbiotics and yeast culture supplementation, and 0.1% SYB had the best alleviating effect. Dietary 0.1% SYB supplementation also increased serum IL-10, IgM, C4 and jejunal mucosal IL-4 levels, while decreased serum DAO activity compared with CONII group (P < 0.05). Furthermore, 0.1% SYB improved mRNA expressions of Claudin-1, ZO-1, MUC2, IFN-γ, IRF-3, STAT (P < 0.05) and protein expression of Occludin, and down-regulated mRNA expressions of TLR3 and TNF-α (P < 0.05) in jejunal mucosa. Supplementing 0.2% SYB or 0.2% YC also had a positive effect on piglets, but the effect was not as good as 0.1% SYB. These results indicated that dietary 0.1% SYB supplementation improved growth performance under normal conditions, and alleviated the inflammatory response and the damage of intestinal barrier via improving innate immune function and decreasing PEDV genomic copies, showed optimal protective effects against PEDV infection.