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New probiotic Bacillus strain improving gut health in piglets
The scheduled phase-out of specific antibiotic growth promoters in the US requires management changes in the pig industry and a need for cost-effective feed additives with high efficacy and thus the need for new probiotics. The objective of this work was to screen 260 new spore formers isolated from fermented food, healthy pig faeces, soil and different culture collections, and to select 2 candidates for in vivo trials. One candidate is presented in this paper. The strain was identified as Bacillus subtilis subsp. subtilis by sequencing of 16S rDNA and gyrB and rpoB gene, its antibiotic susceptibility was measured by the minimal inhibitory concentration (MIC) and found to below the accepted breakpoints. Other analyses included bile and acid tolerance, growth in different media, sporulation and antimicrobial activity against Clostridium perfringens Type A and Type C as well as Salmonella typhimurium and Staphylococcocus aureus. In vitro adhesion to Caco-2 and HT-29 MTX cell lines was also investigated. For the in vivo trial 216 four weeks old newly weaned piglets were randomly allocated to control or Bacillus subtilis (DSM25841) treatment group respectively balanced for sex and liveweight. Piglets were fed equal standard diets based on corn, soybean and barley strain or none Bacillus spp.
Adhesion to Caco-2 cell line was 6.2 ± 1.3 in contrast to HT-29MTX, for which the selected strain showed a significantly higher coefficient (42.2 ± 5.6). Moreover, the selected strain showed higher adhesion to both cell lines when compared to another potential Bacillus spp. candidate identified by this study. For the latter, the adhesion coefficients to Caco-2 and to HT-29 MTX were 2.1 ± 0.4 and 32.3 ± 3.7, respectively. Our data are in agreement with similar in vitro studies conducted on other probiotic Bacillus spp. and emphasize the ability of our selected candidate to adhere in vitro, and the differences in characteristics and functions exhibited by the two cell lines.
Results showed that feed supplementation with the selected Bacilli strain DSM 25841 had numeric or significant effect on daily gain (235 g/day vs. 218 g/day) and feed conversion (1.15 kg/kg vs. 1.21 kg/kg; P<0.05) as well as improved faecal scoring (P<0.01) compared to the control group.
Keywords: Bacillus probiotic, adhesion, pig production