Antimicrobial use in poultry is a global concern as antimicrobial use in animals contributes to antimicrobial resistance with potential impact on animal, environmental and public health. Antimicrobial use in poultry in Denmark is relatively low compared to the use for other animal species, i.e. only 1-2% of the total antimicrobial use in kg active compound for animals in Denmark in 2015-2021. Knowledge about the distribution of antimicrobial use between poultry herds
and herd types is lacking. The objective of this study was to quantify antimicrobial use at herd level in the Danish broiler sector. We obtained data on antimicrobials prescribed for poultry herds from 2015-2019 from the VetStat database; a national public database that has collected sales data on medical products prescribed for animals in Denmark since 2000. To quantify antimicrobial use at herd level, we obtained data about herd sizes from the Danish Zoonoses database with records of all active Danish conventional (n=238) and organic broiler herds (n=32), and conventional broiler breeder (n=47) and broiler breeder pullet herds (n=22) in 2015-2019. Antimicrobial use was quantified as Animal Daily Doses (ADD) per 1,000 birds per herd-month. The results showed that antimicrobials were used in 969 of 17,927 (5.4%) herd-months in 2015-2019 across the four herd types. In herd-months with antimicrobial use, the median ADD per 1,000 birds per herd-month was 3,199 in conventional broiler herds, 11,532 in organic broiler herds, 6,818 in conventional broiler breeder herds and 1,190 in conventional broiler breeder pullet herds. A lower proportion of organic broiler herds (28.2%) used antimicrobials in at least one herd-month in 2015-2019 compared to conventional
broiler herds (68.1%) in 2015-2019. A lower proportion of conventional broiler breeder herds (63.8%) used antimicrobials in at least one herd-month in 2015-2019 compared to conventional breeder pullet herds (86.4%). We observed a substantial within-herd variation in herds that used antimicrobials in 2015-2019. The results provide new insights into how antimicrobial usage patterns in the Danish broiler sector are distributed over time, within herds and between herd types. Further studies are needed to understand the reasons behind the relatively low use of antimicrobials in the Danish broiler sector and the associations with health, welfare and management, including use of vaccines. Such investigations may require both field investigations, interviews and register-based research to enable development of recommendations to ensure prudent antimicrobial use.