Antimicrobial Use in Livestock Production: History and Impact On Antimicrobial Resistance, Food Safety and the Environment.

While antimicrobials are used in US livestock production for disease treatment, they can also be included in the feed as a means to prevent disease and, in some cases, improve growth efficiency.  The inclusion antimicrobials in livestock feed, however, is one of the more controversial agricultural practices in the US.    Most concerns center on the development of antibiotic resistant bacteria and its implications for human health.  In many cases, antimicrobials are poorly absorbed by the animal, and in recent years there has been growing concern over the impact that excreted antimicrobials may have on the terrestrial environment as well.  Here we will discuss the history of antimicrobial use in US livestock production, focusing on the mechanisms involved in antimicrobial-associated improvements in growth efficiency.  We will also examine the impact of this practice on antimicrobial resistance both on and off the farm and research examining the fate of unabsorbed antibiotics in the environment.  We will also present data from several projects in our laboratory aimed at developing non-antimicrobial technologies that effectively limit transmission of pathogenic bacteria in live animals and during their processing.  Finally, we will discuss potential changes in policies regarding antimicrobial use in US agriculture and the impact that these changes may have on livestock production, animal health and human medicine.