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Background: The interest on probiotics as a potential substitute for antibiotics is rising, however, little is known about Bacillus dietary supplementation to counteract piglet ETEC infection. This study investigated the effect of Bacillus amyloliquefaciens DSM25840 or Bacillus subtilis DSM25841 supplementation on growth, health, immunity, intestinal functionality and microbial profile of F4-ETEC infected post-weaning pigs.Methods: Sixty-four post-weaning piglets (BW 7748g ± 643g) were randomly allocated to four groups: control basal diet (CO); CO + 28 x 106cfu/g of B. amyloliquefaciens (BAA); CO + 1.28 x 106cfu/g feed of B. subtilis (BAS); CO + 1 g colistin/kg of feed (AB). At day 7, animals were challenged with 105 CFU of E. coli F4ac O149/mL and then followed for faecal score and performance until day 21 (d21). Blood was collected at day (d) 6, d12 and d21 for immunoglobulins, at d8 for acute phase proteins, at d8 and d21 for metabolomics analysis. Jejunum mucosa was sampled for morphometry, quantification of apoptosis, cell proliferation, neutral and acid mucine and IgA secretory cells, and microarray analysis at day 21. Jejunum and cecum contents were collected for microbiota at day 21.Results: AB and BAS (at d14) improved the faecal score compared to CO (P < 0.05). Body weight(BW), Average daily weight gain (ADWG), average daily feed intake (ADFI) and gain to feed ratio (G:F) did no differ between the Bacillus groups and CO. AB improved BW at d7, d14 and d21, ADWG ADFI and G:F from d0 to d7 (P< 0.05). At d8, CO had higher plasma arginine, lysine, ornithine, glycine, serine and threonine than other groups, and higher haptoglobin than AB (P < 0.05). At d21, CO had lower blood glycine, glutamine and IgA than BAS. Morphology, cells apoptosis and mucins did not differ among groups. BAS and AB increased the villus mitotic index. Transcriptome profile of BAS and AB were more similar than CO. Gene sets related to adaptive immune response were enriched in BAA, BAS and AB. CO had enriched gene set for nuclear structure and RNA processing. CO had a trend of higher Enterobacteriaceae in cecum compared to the other groups (P = 0.06).Conclusion Bacillus subtilis DSM25841 treatment may reduce ETEC F4ac infection in weaned piglets, decreasing diarrhoea and influencing mucosal transcriptomic profile. |