Effects of Bacillus Subtilis on Growth Performance, Diarrhea, and Gut Health of Weanling Pigs Experimentally Infected with F18 Escherichia coli

The objective of this experiment was to investigate dietary supplementation of a direct-fed microbials (DFMs), Bacillus subtilis (DSM 25841) on growth performance, diarrhea, gut morphology and permeability of weaned pigs experimentally infected with a pathogenic F18 Escherichia coli (E. coli). Forty-eight pigs (6.73 ± 0.77 kg BW) were individually housed in disease containment rooms and randomly allotted to one of four treatments with 12 replicates per treatment. Four treatments included negative control (NC), positive control (PC), low dose DFMs group, and high dose DFMs group. Pigs in the NC and PC groups were fed with basal diet but without or with E. coli challenge. Pigs in the DFMs groups were fed the diets either supplemented with 1.28 × 10⁹ CFU or 2.56 × 10⁹ CFU Bacillus subtilis/kg feed and challenged with E. coli. The experiment lasted 18 days [7 days before and 11 days after the first inoculation (d 0)]. The inoculum used in this experiment was F-18 E. coli, containing LT, STb, and SLT-2 toxins. The inoculation doses were 10¹⁰ cfu/3 mL oral dose daily for 3 consecutive days. Growth performance was measured on d 0 to 5, 5 to 11, and 0 to 11 post-inoculation (PI). Diarrhea score (DS; 1, normal, to 5, watery diarrhea) was recorded for each pig daily. Twenty-four pigs were euthanized on d 5 and 11 PI, respectively, to collect duodenum, middle of jejunum, and ileum to analyze gut morphology. Jejunum were also freshly collected from 4 pigs per treatment except the low dose DFMs group for transcellular and paracellular permeability analysis. All data were analyzed by ANOVA using the PROC MIXED of SAS. The E. coli infection reduced (P < 0.05) growth performance and intestinal villi height, but increased (P < 0.05) diarrhea and transcellular and paracellular permeability in jejunum compared with pigs in the NC. Supplementation of Bacillus subtilis linearly enhanced ADG of E. coli infected pigs from d 0 to 5 PI (P < 0.05) and 0 to 11 PI (P = 0.058). However, no differences were observed in daily diarrhea score and overall frequency of diarrhea among E. coli challenge groups. Supplementation of high dose of Bacillus subtilis reduced (P < 0.05) both transcellular and paracellular permeability on d 5 and d 11 PI compared with the PC. In conclusion, supplementation of Bacillus subtilis enhanced growth rate and reduced gut permeability of weaned pigs infected with a pathogenic E. coli.