UC Davis

Probiotics and botanical extracts are investigated as potential feed additives for weaned pigs to strengthen the intestinal function or overall immunity by improving nutrient digestibility and immunity in weaned pigs. Under proper manipulation, gut microbiota can additionally offer great physiological and immunological benefits to growing pigs, however, gut microbiota yet tends to be overlooked when assessing the viability of potential feed additives to weaned pigs under diarrheal stress. Therefore, three experiments were conducted to determine the impacts of various feed additives (Bacillus (B.) subtilis, B. amyloliquefaciens, and botanical blends) on gut microbiota of newly weaned pigs using a disease challenge model. The first study investigated modifications in fecal and intestinal microbiota of weaned pigs challenged with enterotoxigenic Escherichia coli (ETEC) and compared the gut microbiota when supplemented with B. subtilis DSM 25841 or carbadox, an antibiotic growth promoter. ETEC infection decreased (P < 0.05) microbial richness in feces on d 7 post-inoculation (PI) compared with d 0 before ETEC infection. Relative abundance of Firmicutes was decreased (P < 0.05) while Proteobacteria and Enterobacteriaceae were increased (P < 0.05) in fecal samples of pigs challenged with ETEC on d 7 PI than on d 0. Supplementation of carbadox reduced (P < 0.05) the relative abundance of Lactobacillaceae in feces on d 0 and 21 PI. Lactobacillus was more (P < 0.05) abundant on d 7 PI and Lactobacillaceae was greater (P < 0.05) in relative abundance on d 21 PI in feces from pigs supplemented with B. subtilis than with carbadox. Among intestinal segments, Enterobacteriaceae was more (P < 0.05) abundant in ileum than in jejunum and colon of weaned pigs on d 21 PI. Pigs supplemented with B. subtilis increased (P < 0.05) the relative abundance of gram-positive bacteria than pigs supplemented with carbadox, including Lactobacillaceae and Bifidobacteriaceae in ileal digesta on d 21 PI. Overall, the present study indicated that B. subtilis supplementation modulated the fecal and intestinal microbiota differently from carbadox. The modulation of gut microbiota might contribute to the reduced diarrhea and enhanced intestinal health of ETEC infected pigs. The second study investigated the supplementation of B. amyloliquefaciens on growth performance, diarrhea, systemic immunity, and intestinal microbiota of weaned pigs infected with ETEC and compared the efficacy of B. amyloliquefaciens vs. carbadox on weaned pigs. ETEC infection reduced (P < 0.05) average daily gain (ADG) from d 0 and 21 PI, gain:feed from d 14 and 21 PI, increased (P < 0.05) frequency of diarrhea during the entire experiment and white blood cell and lymphocyte counts on d 7 and 21 PI when positive control was compared with negative control. B. amyloliquefaciens or carbadox supplementation did not affect diarrheal frequency throughout the experiment. However, carbadox supplementation enhanced (P < 0.05) ADG from d 0 to 21 PI than positive control. Pigs fed with carbadox had greater (P < 0.05) monocyte percentage in serum samples on d 7 and 21 PI but lower (P < 0.05) neutrophil percentage on d 21 PI than pigs fed with B. amyloliquefaciens under ETEC challenge. Pigs supplemented with B. amyloliquefaciens had greater (P < 0.05) Shannon index in ileal digesta than pigs fed with carbadox on d 21 PI. Positive control pigs had a greater (P < 0.05) abundance of Bacteroidota and Proteobacteria and lower (P < 0.05) Firmicutes in ileal digesta than negative control on d 21 PI. Carbadox addition increased (P < 0.05) the relative abundances of Firmicutes and Clostridiaceae but reduced (P < 0.05) Bifidobacterium in ileal digesta compared with B. amyloliquefaciens on d 21 PI. The results of the present study indicated that supplementation of B. amyloliquefaciens tended to increase ADG and had limited effects on diarrhea of ETEC infected pigs. However, pigs fed with B. amyloliquefaciens exhibit milder systemic inflammation than control. B. amyloliquefaciens differently modified intestinal microbiota of weaned pigs, compared with carbadox. The third study characterized the impacts of two types of botanical blends on gut microbiota composition and serum and ileal mucosa metabolites in weaned pigs challenged with ETEC. Botanical blends (BB1 and BB2) were comprised of 0.3% capsicum oleoresin and 12% garlic oil extracted from different sources. Throughout the experiment, the relative abundance of Lachnoclostridium was decreased (P < 0.05) in feces as the age of pigs was increased from d -7 to d 21 PI. ETEC infection reduced (P < 0.05) the relative abundance of fecal Faecalibacterium and Prevotella on d 5 and 21 PI when positive control was compared with negative control. On d 21 PI, the relative abundance of Firmicutes and Lactobacillaceae were lower (P < 0.05) in feces of pigs fed with 100 ppm BB1 than pigs in positive control. Pigs supplemented with 100 ppm BB2 had a greater (P < 0.05) relative abundance of Lachnospiraceae in feces than pigs fed with 100 ppm BB1 on d 21 PI. Pigs in positive control had the highest (P < 0.05) Shannon and Chao1 indices in ileal digesta on d 5 PI. Pigs supplemented with 100 ppm BB1 had greater (P < 0.05) abundances of Enterobacteriaceae and Escherichia-Shigella in ileal digesta than pigs in positive control on d 5 PI. The relative abundance of Prevotellaceae was greater (P < 0.05) in cecum of pigs supplemented with 100 ppm BB1 than positive control pigs on d 5 PI. The metabolomics analysis revealed that ETEC infection downregulated pinitol, malic acid, and methionine on d 4 PI and upregulated methionine and guanosine on d 21 PI when positive control was compared with negative control. Supplementation of 100 ppm BB2 upregulated serum pinitol on d 5 PI and serum cholesterol and aminomalonic acids on d 21 PI compared with positive control. In ileal mucosa, asparagine was downregulated by 50 ppm BB2 in comparison to positive control. The present study indicated that supplementation of botanical blends modulated ileal microbiota and serum metabolomics profiles in weaned pigs under ETEC challenge. Overall, feed additives, including probiotics and botanical blends modified gut microbiota of weaned pigs challenged with ETEC to different extent, which may potentially contribute to reduced diarrhea and enhanced intestinal integrity and health of newly weaned pigs when these feed additives were supplemented into the diet.