Veterinary antibiotics and antibiotic resistance genes in agroecosystems: occurrence, environmental fate, risks, and remediation strategies.

Veterinary antibiotics (VAs) are widely used in livestock and poultry production, but 30-90% of administered doses may be excreted unchanged or as bioactive metabolites, resulting in their continuous release into agroecosystems through manure storage, handling, and land application. As a result, VAs contaminate soils, manure, irrigation water, sediments, and crops, thereby enriching and disseminating antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARBs). This review synthesizes current knowledge on the occurrence, migration, transformation, resistance implications, and mitigation of major VAs classes in agroecosystems, with emphasis on tetracyclines (TCs), fluoroquinolones (FQs), sulfonamides (SAs), macrolides (MCs), and β-lactams. TCs and FQs were the dominant solid-phase contaminants in manure-amended soils. In contrast, SAs showed greater transport potential due to weaker sorption and greater aqueous mobility. Resistance patterns broadly followed these class-specific trends, although ARGs persistence was often decoupled from residue decline due to mobile genetic elements (MGEs) and heavy metal co-selection. Biochar (BCs), nanoparticles (NPs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs) showed promising mitigation performance, but evidence for concurrent reductions in ARGs, ARBs, and transfer potential remains limited. Ultimately, effective risk management requires integrated strategies that simultaneously address residues, resistance determinants, and their environmental dissemination pathways.