Estimates of on-farm antimicrobial usage in broiler chicken production in the United States, 2013-2017.

Antimicrobial use is a key selective force behind the emergence of resistant bacteria. Therefore, optimizing strategies for more efficacious and targeted antimicrobial use is an essential component of efforts to combat antimicrobial resistance. To bolster stewardship programmes in animal agriculture, processes are needed for the systematic collection of on-farm antimicrobial use data. The objective of this study was to develop a system for collecting on-farm antimicrobial use data from the US broiler industry and to have it be representative of the largest commercial broiler producers in the United States that comprise the vast majority of national broiler production. Participation was voluntary. Data were collected for the period 2013 through 2017 and are reported on a calendar year basis. Using statistics from USDA:NASS as a denominator, the data supplied by participating companies accounted for approximately 81.7% of broiler production in the United States in 2013 and increased to approximately 87.2% in 2017. The data that were submitted for 2017 are based on approximately 7,897,339,357 chicks placed, 7,541,449,430 chickens slaughtered and 48,225,124,865 pounds liveweight produced. The use of antimicrobials in the hatchery decreased substantially between 2013 and 2017; the approximate percentage of broiler chicks placed that received hatchery antimicrobials decreased from 93% in 2013 to 17% in 2017. Medically important in-feed antimicrobial use decreased substantially. For example, in-feed tetracycline use decreased approximately 95% between 2013 and 2017. Medically important water-soluble antimicrobial use decreased substantially for most antimicrobials. Between 2013 and 2017, water-soluble penicillin use decreased approximately 21%, water-soluble tetracycline use decreased approximately 47%, and water-soluble lincomycin use decreased approximately 28%. While a reduction in antimicrobial amounts used may be an important indicator of improved stewardship, reducing the need for antimicrobials through improved disease prevention should be considered a more important objective and a better indicator of overall flock health and optimal antimicrobial use.