A field study of Bacillus licheniformis-fermented products on growth performance and faecal microbiota of weaning piglets

This study investigated the effects of Bacillus licheniformis-fermented products (BLFPs) on the growth performance, faecal microbiota, and antibiotic resistance gene (ARG) expression in weaning piglets on a commercial farm. Ninety-six weaning piglets were randomly assigned to four treatments as follows: basal diet as control (C), basal diet plus 30 mg/kg of antibiotics (bacitracin methylene disalicylate) (A), basal diet plus 1 g/kg of BLFPs (F), and basal diet plus 15 mg/kg of antibiotics and 0.5 g/kg of BLFPs (AF), with six replicate pens per treatment and four pigs per pen. Results showed that, similar to antibiotics, replacing all or half the antibiotics with BLFPs improved the feed conversion ratio of weaning piglets from 15–28 d. Microbiota analysis showed that microbial community composition in the faeces showed a clear separation between groups. Replacing all the antibiotics with BLFPs increased the abundance of the genus, Streptococcus, in the faeces compared with the other groups. Half replacement of antibiotics with BLFPs increased the chloramphenicol resistance gene levels in the faeces compared with the C group, whereas full replacement of antibiotics with BLFPs reduced the streptomycin resistance gene levels compared with the C group. A trend of decreased levels of formic acid and acetic acid was observed in the group treated with BLFPs in combination with antibiotics compared with the C group. In conclusion, the field study demonstrates that replacing all or half the antibiotics with BLFPs can improve feed conversion ratio, modulate faecal microbiota, and alter ARG expression in weaning piglets.