Fig. 1

The composition, abundance, and richness of fecal resistome in pigs under different rearing modes. a The abundances and the numbers of antimicrobial resistance genes (ARGs) for each antimicrobial. All ARGs were classified according to the antimicrobial for which they showed resistance. The abbreviated names of antimicrobial classes were used in all figures, and the corresponding full names were presented in Additional file 4: Table S3. b The abundances and the numbers of ARGs in all samples (n = 425). All samples were divided into nine groups according to the farms that the samples were from. All wild boars were considered as one group. Wild represents wild boars; KD-3800, KD-3400, and KD-1400 represent Tibetan pigs raised in three high-altitude farms (3800m, 3400m, and 1400m) from Kangding; NC-Tibetan represents Tibetan pigs raised in Nanchang; NC-F6 represents pigs from a F6 mosaic population raised in Nanchang; Dingnan represents pigs raised in Dingnan; Jiangyin and Shahu represent Duroc pigs raised in Jiangyin and Shahu farms. More details of nine pig populations are shown in Additional file 2: Table S1. c The abundance of 46 core ARGs in each of nine pig populations, and their corresponding antimicrobial classes and resistance mechanisms. The ARGs existed in at least 95% samples (n ≥ 404) were defined as core ARGs in pig feces. Two color bars on the left of the heatmap represent the resistance mechanism and corresponding antimicrobial class of each resistance gene, respectively. The abundance of 46 core ARGs varied greatly in different pig groups