The prevalence of antibiotic resistance in human and veterinary medicine has called attention to the use of antimicrobials in livestock diets to improve growth. The majority of antimicrobial resistance is thought to originate from misuse in human and animal medicine. Although no studies currently link livestock feed antimicrobials with medicinal resistance, bans and restrictions are discussed, and sometimes implemented. A literature review provided only limited results for studies directly comparing low dose administration in feed and solely therapeutic use on the development of antimicrobial resistance. With the lack of evidence for the source of resistance, a conservative approach to the use of antimicrobials – especially as growth promoters – is likely to be taken by the US FDA. The use of antimicrobials will likely be limited in the future, but maintaining animals health (especially in weaner pigs) will hopefully permit the therapeutic use in food animals.