Changes in the gut ecosystems and serum metabolome by a diet supplemented with enramycin in weaning piglets.

Although antibiotics have long been added to feed to promote growth in the livestock industry, there is a global trend to limit the use of antibiotics as growth promoters because they promote the emergence of antimicrobial resistant bacteria and pose a threat to human and animal health. Therefore, effective feed additives are needed to replace antibiotics and detailed analysis of changes in gut microbiota and growth promotion after antibiotic administration is essential to find effective alternatives. In this study, changes in the gut microbiota were analyzed using 16S rRNA gene amplicon sequencing. The analysis showed that alpha diversity increased in the antibiotic-treated group and beta diversity was significantly different between the control and antibiotic-treated groups. Furthermore, we focused on the species level, Limosilactobacillus reuteri increased in the antibiotic-treated group, and Limocilactobacillus mucosae and Lactobacillus delbrueckii decreased. This study showed that antibiotic supplementation at sub-therapeutic concentrations created a rich microbiota and changed the composition of Lactobacillus species, including L. reuteri. This may result in an increase in growth efficiency due to improved feed utilization efficiency.