PSII-15 Dietary Supplementation of Bacillus Subtilis Modified Intestinal Microbiome of Weaned Pigs Differently to Antibiotics

Abstract The objective of this study was to compare the dietary effects of Bacillus subtilis and antibiotics in intestinal microbiota of pigs experimentally infected with F18 E. coli. Forty-eight weaned pigs (6.17 ± 0.36 kg BW) were individually housed and randomly allotted in one of four treatments with 12 replicates per treatment: negative control (NC), positive control (PC), antibiotics, and B. subtilis (probiotics). Pigs in NC and PC were fed with basal diet without or with E. coli, respectively. Pigs with antibiotics and probiotics were challenged with E. coli and supplemented with 50 mg/kg of carbadox or 500 mg/kg of B. subtilis, respectively. After 7 days habituation period, pigs were inoculated with F18 E. coli at 1010 CFU/3 mL dose for three consecutive days. All pigs were euthanized to collect feces and digesta from jejunum, ileum, and colon on d 21 post-infection to perform 16S rRNA sequencing at the V4 hypervariable region. Downstream analysis was performed using QIIME2 (2019.4) and R. Kruskal-Wallis test followed by Conover test was used to analyze data in R. Colon digesta and feces have greater (P < 0.05) alpha diversity than ileal and jejunal digesta. No difference was observed among treatments at different intestinal sites. Bray-Curtis PCoA plots displayed pronounced clusters of all treatment groups throughout all sites. Bacteroidetes and Proteobacteria were more (P < 0.05) abundant but Firmicutes were less (P < 0.05) abundant in ileal digesta of pigs fed with antibiotics than pigs in probiotics. Firmicutes were more (P < 0.05) abundant in colon and feces of NC than of antibiotics. Bifidobacterium was least (P < 0.05) abundant throughout all sites and Prevotella 1 was most (P < 0.05) abundant in colon of pigs fed with antibiotics compared with other treatments. In conclusion, both B. subtilis and carbadox supplementation modified gut microbiota of weaned pigs challenged with F18 E. coli. However, the impacts are different and need further investigation.