Date Full Report Received

Date Abstract Report Received


Primary Investigator:

Producing pigs without using antibiotic growth promoters represents a big challenge in swine industry. Disease problems often are elevated and general performance is compromised on farms practicing non-medicated swine production, in particular during the immediate post-weaning period. Because of the difficulties associated with producing pigs without antibiotics, many producers are looking for alternative growth promoters, although no ‘magic bullets’ are available. The benefits of dietary probiotics have been widely approached, however, the research on modes of action are still limited. This experiment aims to investigate several key points related to a probiotic strain, Bacillus subtilis: 1) effects of probiotics on disease resistance, 2) impacts of probiotics on gut health, especially gut microbiome and their metabolites, and 3) comparison of influences of dietary probiotics vs. carbadox. To investigate these objectives, 48 weaned pigs were used and individually housed in the environmental controlled rooms at Cole facility at the University of California, Davis. Pigs were randomly allotted to one of four treatments: 1) negative control, pigs fed with control diet without F18 E. coli challenge, 2) positive control, pigs fed with control diet with F18 E. coli challenge, 3) antibiotic group, pigs fed diet supplemented with 50 mg/kg of carbadox with F18 E. coli challenge, and 4) probiotics group, pig fed diet supplemented with 500 mg/kg of Bacillus subtilis probiotics with F18 E. coli challenge. The experiment lasted 28 days with 7 days adaptation and 21 days after the first F18 E. coli inoculation. Data were recorded, and blood and fecal samples were collected throughout the experiment. Overall, this experiment demonstrates that in-feed supplementation of Bacillus subtilis enhanced disease resistance of weaned pigs as indicated by reduced frequency of diarrhea during the entire experimental period. Supplementation of Bacillus subtilis enhanced growth performance of F18 E. coli infected pigs. These benefits are closely related to two modes of action. First, pigs supplemented with Bacillus subtilis had a much milder intestinal inflammation and systemic inflammation compared with E. coli infected pigs fed with control diet. Second, supplementation of probiotics modified gut microbiome and their metabolites by enhancing the relative abundance of beneficial microorganisms. Although pigs supplemented with Bacillus subtilis were not able to completely catch up with the performance of pigs in antibiotics group, they had similar final body weights compared with negative control pigs that were not infected with E. coli. Results of this experiment also indicated that Bacillus subtilis and antibiotics had remarkably different impacts on gut microbiome of weaned pigs. More research is needed to explore these differences, especially focusing on the development of antibiotic resistant bacteria in pigs fed with probiotics vs. antibiotics. Taken together, this study confirms the growth promoting effects of in-feed Bacillus subtilis, which will be a great add-up to the complicated nutritional strategies used to increase profitability of pork producers as the use of antibiotics in feed is restricted.