Fig. 2

Comparisons of the abundances and the gene numbers of antimicrobial resistance genes (ARGs), and the α-diversity of bacterial composition among experimental pigs from nine populations. a Comparisons of the abundances of ARGs among nine populations. b Comparisons of the richness of ARGs among nine populations. c Comparisons of Shannon index of gut microbiota at the species level among nine populations. d Comparisons of Simpson’s index of gut microbiota among nine populations. The pigs showing the lower diversity (Shannon index and Simpson’s index) of gut microbiota tend to have higher ARG abundance and richness. The boxplots are colored according to the rearing modes (green: free-range living, blue: semi-free ranging, red: standard farm housing). Numbers in brackets of x-axes represent the sample number of each group