Calcium Peroxide Addition Suppresses ARG Dissemination by Modulating Host Succession and MGE-Mediated Horizontal Transfer During Swine Manure Composting

Applying exogenous additives during composting can help to effectively mitigate the environmental dissemination of antibiotic resistance genes (ARGs). Calcium peroxide (CaO2)—a strong oxidizing agent—has achieved significant efficacy in degrading various pollutants. This study aims to evaluate the effects of CaO2 at varying doses (0, 1% and 3% DW) on the variation in ARGs, mobile genetic elements (MGEs), and bacterial community succession during swine manure composting. Compared to the control (CK), adding 1% and 3% CaO2 reduced total ARGs and MGEs by 50.29% and 64.62% in the LCP and by 68.96% and 79.74% in the HCP treatment, respectively. Adding 1% and 3% CaO2 significantly increased the relative abundances (RAs) of Actinobacteriota and Firmicutes while decreasing those of Proteobacteria and Bacteroidetes during the thermophilic phase, especially under the high-dose treatment. Redundancy analysis (RDA) revealed that MGEs accounted for 54.20% of the total variation in ARGs, followed by environmental factors (30.3%). Network analysis further revealed that 1% and 3% CaO2 treatments disrupted the association between ARGs and their host bacteria. Overall, adding CaO2 can reduce the risks of spreading ARGs in compost products.