Early weaning induces villous atrophy in the small intestine (SI) of piglets. Oral administration of live lactic acid bacteria (LAB) can improve villous shortening. In this study, we evaluated the oral administration of a heat-killed and dried cell preparation of Enterococcus faecalis (a LAB) strain EC-12 against villous atrophy in early-weaned mice (Experiment 1) and pigs (Experiments 2 and 3). Twelve 16-days-old mice were divided into two groups in Experiment 1: gavage of EC-12 (10 mg/kg body weight (BW)/day), or control. On day 21, SI was collected. Eighteen 21-day-old pigs were divided into two groups in Experiment 2: gavage of EC-12 (10 mg/kg BW/day), or control. After 10 days, the villous height of jejunum was measured. Six 21-day-old pigs were divided into two groups in Experiment 3: the basal diet supplemented with EC-12 at 0.05%-fed group, or the basal diet-fed group. After 10 days, the villous height of jejunum was measured. The villous heights in SI were significantly higher by EC-12 administration in all experiments. EC-12 successfully improved the villous atrophy in the early-weaned mice and pigs when EC-12 was administered orally.

Weaning piglets are continuously exposed to various viruses. The antiviral effects of lactic acid bacteria (LAB) have been confirmed mainly in humans and mice, while few studies have been conducted in livestock. In this study, we evaluated the effect of oral administration of Enterococcus faecalis strain EC-12 (EC-12) on the gene expressions of antiviral cytokines in weaning piglets. Piglets were allocated to the EC-12-administered group (E group) and the no-treatment control group (C group). The small intestinal tissue, the mesenteric lymph node (MLN) cells and the splenocytes were collected from the piglets. The tissue and cells were co-cultured with a live vaccine of porcine reproductive respiratory syndrome virus, porcine epidemic diarrhea virus or EC-12. After the incubation, the gene expressions of IFN-γ and TNF-α in the tissue and cells were evaluated. The gene expressions of IFN-γ in the MLN cells and TNF-α in the splenocytes were significantly higher in the E group than in the C group. However, the increase in the gene expression of antiviral cytokines was observed independently of the antigen treatments. The results of the present study suggest that oral administration of EC-12 did not increase the response of immune cells to specific viral antigens but increased the baseline gene expression of antiviral cytokines.