Doxycycline-induced toxic perturbations on manure GHG potential: Phage-microbe interactions and BSF pretreatment...

The large-scale production of poultry manure poses significant environmental safety challenges, and Black Soldier Fly (BSF) has emerged as a potential resource utilization solution. However, the toxicological effects of doxycycline (DOX) contamination in poultry feces on methane (CH₄) and nitrous oxide (N₂O) emission potential throughout the BSF manure recycling process remains unclear, especially from a phage-microbe interaction perspective. This study investigates the roles of bacterial and phage-related functional genes associated with CH₄ and N₂O metabolism in the "chicken manure-organic fertilizer" and "chicken manure-BSF-chicken" pathways. The results reveal that DOX in poultry manure causes toxicological perturbations of the microbial community, significantly elevating the levels of key functional genes (mcrA/pmoA and (nirS+nirK)/nosZ) linked to GHG emission potential. These DOX-induced elevated gene levels persisted in BSF-derived organic fertilizer and in the feces of laying hens fed BSF reared on contaminated manure. However, 24-hour starvation pretreatment combined with 8-hour drying at 65 °C can effectively alleviate the negative toxicological effects induced by DOX, and the emission potentials of CH₄ and N₂O in the feces of laying hens fed BSF treated in this way were reduced by 91.1% and 82.4%, respectively. Importantly, phage-mediated horizontal gene transfer (HGT) plays a significant regulatory role in these gene changes, further amplifying the DOX-induced GHG emission risk. This study highlights the potential of BSF pretreatment to reduce the environmental risk of antibiotic-contaminated poultry manure while addressing climate concerns from an environmental toxicology perspective. It also provides a scalable toxicological risk mitigation strategy to reduce greenhouse gas emission potential in poultry farming systems, which is of great significance for the environmental safety of intensive poultry production.