Fate of veterinary antimicrobials in Canadian prairie soils - A critical review

Veterinary antimicrobials (VAs) widely used in intensive livestock production are excreted in livestock manure. Manure is an essential component in agriculture for recycling critical nutrients and improving overall soil health. However, manure application on agricultural lands increases the risk of contaminating the ecosystem with antimicrobials. Antimicrobials in manure-amended soils can affect ecosystem functioning via their negative effect on biogeochemical cycles and increase human exposure. Also, the release of antimicrobials to the broader environment, including that arising because of offsite transport, is linked to the global increase in antibiotic resistance in bacteria. Antibiotic resistance is an emerging global threat to human health, particularly the pathogenic bacteria resistant to the main antimicrobial classes in use. Therefore, there is a need to review current literature to enhance our understanding of the fate of these contaminants across agricultural landscapes. This review focuses on (1) a detailed discussion of sorption mechanisms by exploring the structural attributes of antimicrobials, (2) specific sorption interactions with active adsorbent components in the soil as these comprehensive data are important to identify the sorption strengths of antimicrobials which control their fate in the ecosystem, and (3) the effects of on-farm management practices on VA transport and is focused on manure amendment and tillage practices. The key facts identified in this review are critical to identifying sustainable on-farm management practices to enhance the productivity of arable agricultural lands in Canada and across the globe while minimizing the risk of offsite transport of VAs. Further, the research gaps highlighted in the relevant sections are important to designing future research in Canada and globally under similar to variable land/farm management practices.