Enterotoxigenic Escherichia coli (ETEC) is a major cause of post-weaning diarrhea (PWD) in pigs and causes significant damage to the swine industry worldwide. In recent years, there has been increased regulation against the use of antibacterial agents in swine due to their health risks. Utilizing experimental models that consistently recapitulate PWD is important for the development of non-antibacterial agents against PWD in pigs. In this study, we established a highly reproducible PWD infection model by examining differences in adhesion of ETEC to the intestinal tissue as well as the association between MUC4 polymorphisms and sensitivity to PWD. Post-weaning diarrhea differences between pig breeds were also examined. The adhesion to enterocytes varied from 104.0 to 106.4 CFU/mL even among the F4 ETEC strains. Experimental infection revealed that PWD can be induced in all MUC4 genotypes after infection with 1010 CFU/pig of highly adherent ETEC, although there were variable sensitivities between the genotypes. Lowly adherent ETEC did not cause PWD as efficiently as did highly adherent ETEC. The incidence of PWD was confirmed for all pigs with the ETEC-susceptible MUC4 genotypes in all of the breeds. These results indicate that high-precision and reproducible experimental infection is possible regardless of pig breeds by controlling factors on the pig-end (MUC4 genotype) and the bacterial-end (adhesion ability).

Diarrhea can lead to mortality and delayed growth in pigs and is a major economic loss in the pig industry. In this study, we evaluated non-antimicrobial materials that can prevent diarrhea to infection by enterotoxigenic Escherichia coli (ETEC) in weaned pigs and investigated biological changes. We confirmed the efficacy of fumaric acid, lactic acid, Enterococcus faecalis strain EC-12 (EC12) and sugar cane extract (SCE) in inhibiting diarrhea and investigated the biological changes by analyzing gut microbiota and plasma metabolites. Administration of EC12 (0.1%, w/w) and SCE (1.0%, w/w) groups had reduced score of diarrhea. Furthermore, the combination of EC12 and SCE was effective at reducing the fecal score of diarrhea even at low concentrations. Administration of either EC12 or SCE greatly reduced the relative abundance of Enterobacteriaceae in pigs. EC12 and SCE were most effective in suppressing ETEC-induced diarrhea in weaned pigs. Furthermore, we were able to identify biological changes in pigs when EC12 and SCE were administered to pigs. These feeds may have prevented infection by ETEC in weaned pigs and may improve pig productivity and reduce the use of antimicrobial agents.