The influence of farm type on antimicrobial use in dairy cattle and finisher pigs: A comparative study based on Swiss reporting data

Given the increasing threat of antimicrobial resistance to human health, the frequent antimicrobial use (AMU) in livestock remains a topic of serious debate. The identification of AMU-increasing factors is crucial to implement effective measures to reduce overall AMU in livestock. This study used data from the Swiss reporting system to estimate AMU in dairy cattle and finisher pigs, comparing AMU between specialized farms housing either one production category or mixed farms housing both species alongside. Treatment incidence (TI) was calculated based on defined daily doses (DDD) at the farm level (_F) and the population level for each farm type (P_). For dairy farms, we estimated a median TI_F of 4.9 DDD/cow/year and TI_P of 5.8 DDD/cow/year. For dairy cattle on mixed farms, the median TI_F was 5.6 DDD/cow/year and TI_P was 6.4 DDD/cow/year. For finisher farms, we estimated a median TI_F of 0.1 DDD/finisher/year and TI_P of 1.0 DDD/finisher/year. For finisher pigs on mixed farms, the median TI_F was 0.0 DDD/finisher/year and TI_P was 0.4 DDD/finisher/year. This study revealed that mixed farms had a significantly higher AMU for dairy cattle and a significantly lower AMU for finisher pigs compared to the specialized single-species farms. The herd sizes did not correlate with the AMU levels on the farms, and there were no substantial differences in herd size between the different farm types. This suggests that the species housed on the farm and associated management practices, such as animal monitoring, may significantly influence AMU. However, due to the lack of information about farm-level management and husbandry practices, the specific causes for differences in AMU remain speculative.