Limiting and reducing antimicrobial usage (AMU) in animal production is crucial for reducing the human treatment failure caused by antimicrobial resistant (AMR) bacteria. The pig industry accounts for ~80% of all antimicrobials used in the Danish animal production, and this study aimed to identify temporal and structural factors influencing AMU in the Danish pig industry from 2018 to 2023. The primary goal was to estimate how the AMU in pig herds was influenced by the nationwide ban of zinc oxide usage in July 2022, as well as the influence attributed to the management practices of the individual farms and veterinarians.
Farm data and farm-specific AMU data was extracted from national databases. The data was combined and structured around monthly observations of AMU within each pig herd, measured as the average number of Defined Animal Daily Doses (ADDkg) used per pig-day. The data consisted of three levels – 1) observations of within-herd AMU, 2) on farms, 3) overseen by individual veterinarians – and was analysed in a linear mixed-effect model.
The study showed that individual farm management was the main predictor of within-herd AMU, influencing AMU a lot more than individual veterinarian practices. Additionally, the absence of zinc oxide increased AMU in all weaner herds and resulted in a short-term decreased AMU in finisher herds. We also found that the AMU within herds was reduced over time, except in weaner herds from farms where the production had been dependent on zinc oxide prior to the ban. Finally, we found that relocating and/or trading pigs between the weaner and finisher stage in the rearing pathway increased AMU in both stages.
Josefine Ostenfeld Nielsen’s presentation