144 Past and present antimicrobial use in swine production: Raising pigs responsibly.

Abstract Antimicrobials are a tool for treatment, control, and prevention of bacterial disease. The last decade has seen a rapid change in veterinary, producer, consumer, and regulatory attitudes about who, what, when, why, and how antimicrobials are applied during pork production. Antimicrobial resistance (AMR) burden of human infections to medically important classes is the concern. A seemingly logical, yet overly simplified, approach to combatting AMR is to “just use less.” Annually, FDA reports how many milligrams of antimicrobial drugs for use in food-producing animals are sold by species. Following changes in antimicrobial policy outlined in Guidance for Industry (GFI) #209, GFI #213 that took effect on January 1, 2017, a significant decline in the volume of antimicrobials sold for use in swine occurred that year compared to the prior year, 2016. Trends in total milligrams have been unchanged since 2017. Nevertheless, this policy change had a profound impact resulting in a decrease in milligrams of antimicrobial sold, re-enforcing the philosophy of “just use less” and demands for reduction are incorporated into AMR action plans of the United Nations and food retailers. After GFI #213, FDA proceeded to GFI #263 which brought the last of the medically important drugs under veterinary oversight in 2023. While it is too soon to tell what effect this policy has on total milligrams of antimicrobials sold for swine, sales data will always be prone to artifacts. One such artifact occurred as the result of a penicillin shortage in 2021 and is the only known event, outside of policy changes, that produced discernable shifts in the data1. However, the principles of antimicrobial stewardship (AMS) do not mention reduction as part of responsible medical decision-making; rather, AVMA outlines them as the act of making a commitment, preventing disease, judicious use, evaluating use practices, and building expertise. To assess responsible use, granular data should be captured. Davies and Singer demonstrated that antimicrobial distribution data could be voluntarily obtained2. Nine producers representing 20% of the market hogs slaughtered in the United States participated in a project to better characterize use in production settings. A voluntary effort of turkey and broiler producers has captured the nuances of AMU by flock, dose, diagnosis, morbidity, and outcome3. These small purposeful projects inform AMS in a way that country-level sales data and biomass measures do not. Another tool that supports AMS is antimicrobial susceptibility testing (AST). Similarity networks identified unique farms that could be playing a role in bacterial AMR diversity. Machine learning applied to AST results can predict a bacteria’s AMR burden. This progress in AMS tools is remarkable. Presently, responsible AMU depends on those involved in raising pigs practicing AMS.