Characterizing the fate of antimicrobials in manure and agricultural soils

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The Canadian livestock industry annually uses about one million kg of antimicrobial active ingredients for therapeutic administration and sub-therapeutic growth promotion. Antimicrobials are readily excreted and hence detected in manures. Livestock manure laden with antimicrobials and other organic contaminants is applied to agricultural soils without pre-treatment. Prairie farmers need manure to recycle nutrients and increase carbon inputs to improve soil health. Manure can also increase carbon sequestration to mitigate climate change and help Canada's pledge to net-zero emissions by 2050. However, manures spread antimicrobials in the agroecosystem, which can negatively affect the ecosystem's functioning and are linked to antibiotic resistance. Antibiotic resistance is one of the top ten public health emergencies facing the world, declared by the World Health Organization in 2020, and comes at a very high cost to national economies and a burden to the health care systems. If manures continue to spread antimicrobials, their adverse effects on the environment and human health will threaten the future of the prairie livestock cropping systems. Thus, it is critical to act now to lower antimicrobials discharging into the broader environment from livestock operations. My long-term research goal is to characterize the fate of contaminants of agricultural origin in the agroecosystem to advance manure management strategies for sustainable crop-livestock systems in the Canadian Prairies: including the transport, sorption, and degradation of antimicrobials, steroidal hormones, growth promotants, trace elements, and excess nutrients. Data generated by my research will lead to direct applications at the farm level, improve the predictive ability of contaminant transport models under prairie conditions, and aid in developing related policy tools. The short-term objectives to accomplish the above goals are to (1) quantify the extent to which spring-thaw snowmelt runoff and (2) rainfall-runoff and leaching contribute to the transport of dissolved and sediment-bound veterinary antimicrobials, antimicrobial degradation products, and antimicrobial-resistant genes within swine manure-amended cropland; (3) optimization of degradation kinetics of commonly used veterinary antimicrobials, antimicrobial degradation products, and antibiotic-resistant genes during aerobic swine manure composting. The proposed research will generate scientifically sound on-farm livestock manure management strategies and policy tools for sustainability in agriculture. The program will train one MSc, two PhD, and ten undergraduate students (two trainees per year) in soil science, environmental chemistry, analytical chemistry, molecular biology, experiment designs, data analysis, data interpretation, and research communication. The program will also provide opportunities for professional development and networking for the trainees.