Trends and correlates of antimicrobial use in broiler and turkey farms: a poultry company registry-based study in Italy.

Background: Antimicrobial usage (AMU) in livestock plays a key role in the emergence and spread of antimicrobial resistance. Analysis of AMU data in livestock is therefore relevant for both animal and public health. Objectives: To assess AMU in 470 broiler and 252 turkey farms of one of Italys largest poultry companies, accounting for around 30% of national poultry production, to identify trends and risk factors for AMU. Methods: Antimicrobial treatments administered to 5827 broiler and 1264 turkey grow-out cycles in 201517 were expressed as DDDs for animals per population correction unit (DDDvet/PCU). A retrospective analysis was conducted to examine the effect of geographical area, season and prescribing veterinarian on AMU. Management and structural interventions implemented by the company were also assessed. Results: AMU showed a 71% reduction in broilers (from 14 to 4 DDDvet/PCU) and a 56% reduction in turkeys (from 41 to 18 DDDvet/PCU) during the study period. Quinolones, macrolides and polymyxins decreased from 33% to 6% of total AMU in broilers, and from 56% to 32% in turkeys. Broiler cycles during spring and winter showed significantly higher AMU, as well as those in densely populated poultry areas. Different antimicrobial prescribing behaviour was identified among veterinarians. Conclusions: This study evidenced a decreasing trend in AMU and identified several correlates of AMU in broilers and turkeys. These factors will inform the design of interventions to further reduce AMU and therefore counteract antimicrobial resistance in these poultry sectors.