Degradation regulation of monensin in chicken manure and its impact on microbiota in chicken manure

【Objective】 The purpose of the study was to reveal the regulation of degradation of monensin in chicken manure and its tendency in the environment，which would provide theoretical basis for evaluating the ecotoxic effect of monensin used as a feed drug additive，and the support for the harmless treatment of livestock and poultry manure. 【Method】 A high performance liquid chromatography tandem mass spectrometry（LC-MS/MS）method was established for the rapid determination of manure monensin residue，and a model of chicken manure for monensin was constructed. Total DNA of chicken manure was extracted，and high-throughput sequencing was completed by the Illumina NovaSeq 6000 platform，and the results of the sequencing were processed by using Trimmomatic（v0.33）. Then，the OTU clustering analysis，species annotation，Alpha and Beta diversity analysis，significance of differences between groups and correlation analysis were performed to predict the effect of monensin residue on the microbiota in chicken manure compost. 【Result】 The accuracy and precision of LC-MS/MS for the determination of monensin residue in chicken manure were well，with a limit of detection of 0.10 μg/kg and a limit of quantification of 0.25 μg/kg. The degradation half-lives of mo‐ nensin in low（40 μg/g），medieum（80 μg/g），high（120 μg/g）concentrations were 111.95，287.55 and 374.59 d，that was，the higher the concentration of monensin，the longer the half-life of the degradation in chicken manure. The relative abundance of the Firmicutes showed extremely significant decrease（P<0.01）with time when monensin was added to chicken manure. The monensin also altered the relative abundance of dominant genera in chicken manure. The species abundance and diversity of manure microbiota decreased initially，while these indicators increased over time. Chemical heterotrophy was the main metabolism of the chicken manure microbiota，followed by oxidative heterotrophy，hydrocar‐ bon degradation，fermentation and nitrification. Monensin induced Halomonas to change the composition of denitrifying bacteria and decrease denitrification. 【Conclusion】 The determination of monensin residue in chicken manure by dispersive solid-phase extraction coupled with LC-MS/MS is rapid，sensitive and reliable，which can be applied to the detection of real samples. The degradation of monensin in chicken manure is positively correlated with its concentration，and the higher the concentration，the longer the half-life in chicken manure. Monensin can change the composition of microbiota in chicken manure composting process，then affect the fertility of chicken manure compost.