Integrated metagenomic and genomic analysis reveals varying roles of dietary iron and metal-based alternative growth promoters in modulating resistome in postweaning pigs

High levels of zinc oxide (ZnO) and copper sulfate are widely used as alternatives to antibiotic growth promoter in postweaning pig diet. These practices increase heavy metal excretion and raise concerns about environmental contamination and the dissemination of antimicrobial resistance (AMR). Dietary iron availability may influence the gut microbiota and pathogen virulence, but its impact on AMR is unclear. This study utilized an integrated metagenomic and genomic approach to investigate how dietary iron and metal-based growth promoters affects the fecal resistome in post-weaning pigs.