Gastrointestinal ecosystem and immunological responses in E. coli challenged pigs after weaning fed liquid diets containing whey permeate fermented with different lactic acid bacteria

• Pigs were fed with whey permeate (WP) fermented with different lactic acid bacteria.
• Weissella viridescens-fermented WP improved gut health of E. coli inoculated pig.
• Weissella viridescens-fermented WP did not significantly reduce the frequency of diarrhoea in piglets post weaning.

The objective of this study was to investigate the effect of feeding liquid feed containing whey permeate (WP) fermented with different lactic acid bacteria (LAB) on the microbiota and mucosal immune responses of Escherichia coli F4 inoculated piglets post weaning. The study consisted of 52 weaned piglets allotted to 6 treatments: (1) no infection and no WP (INF−WP−); (2) infection and no WP (INF+WP−); (3) infection and non-fermented WP (INF+WP+); (4) infection and WP fermented with Streptococcus thermophilus and Lactobacillus bulgaricus (INF+WP+LAB1); (5) infection and WP fermented with Lactobacillus plantarum (INF+WP+LAB2); and (6) infection and WP fermented with Weissella viridescens (INF+WP+LAB3). Piglets in groups 2 to 6 were inoculated with E. coli F4 on day 2 and 3 after weaning. Faeces were collected on days 2, 3, 4, 5, 6 and 8 and the pigs were sacrificed on day 11. Digesta and mucosa were collected from the GIT segments. Lactic acid concentration was higher (P < 0.05) in the stomach of the INF+WP+LAB3 fed piglets than in the other piglets, but the difference was not significant compared to the INF+WP+LAB1 and INF+WP+LAB2 fed piglets. Compared to the control diet, the fermented WP diet tended (P = 0.069) to lower total coliform and enhanced (P = 0.050) LAB:coliform ratio in GIT digesta. The faecal LAB:coliform ratio was higher (P < 0.05) in the INF+WP+LAB3 fed piglets than in the other piglets, but the difference was not significant compared to the INF+WP+LAB2 fed piglets. Intestinal immunoglobulin (Ig) A decreased (P < 0.05) when feeding WP or W. viridescens-fermented WP. Feeding W. viridescens-fermented WP upregulated (P < 0.05) ileal interleukin (IL)-10 expression. In conclusion, provision of liquid feed containing W. viridescens-fermented WP improved the intestinal health of E. coli inoculated pigs.