Effects of multiple antibiotics residues in broiler manure on composting process

At present, the effect of multiple antibiotics on aerobic composting process and its mechanism are not clear. So in this study, broiler manure containing different doses of Doxycycline (DOX) and Gatifloxacin (GAT) were used as raw materials and mixed with rice hull for aerobic composting, and the effects of the combination of multiple antibiotics on the process parameters of broiler manure composting and the succession of bacterial and fungal community structures were systematically analyzed. Our results showed that at the initial period of composting, the combination of multiple antibiotics led to a delayed temperature and pH increase (T1: 57.0 °C, T2: 48.3 °C, T3: 45.5 °C on Day 3 for temperature and T1: 7.44, T2: 7.1, T3: 6.88 on Day 5 for pH), and a slow total nitrogen decrease (T1: 1.56%, T2: 1.82%, T3: 1.74% on Day 5). Although these effects decreased gradually with the degradation of antibiotics, the relative abundance of Actinobacteriota (T1: 13.29%, T2: 10.57%, T3: 8.99%) and Bacteroidota (T1:27.52%, T2:40.03%, T3:39.81%)) were still influenced by multiple antibiotic residuals until the end of composting period. Higher levels of antibiotics had more lasting effects on the bacterial community (T3 > T2). However, the combination of these two antibiotics did not significantly promote or inhibit the succession of the fungal community structure. The heatmaps showed that composting stage had a greater effect on the microbial community structures than antibiotics. The results provided a theoretical reference for composting broiler manure containing DOX and GAT.