Association between antimicrobial use levels and meat inspection lesions in Danish finishers

In Denmark, the Yellow Card scheme enforces restrictions on pig herds exceeding official permitted limits for antimicrobial use (AMU). To assess if a Yellow Card is related to poor animal health, we examined the association between AMU and the health status of Danish finishers using meat inspection data as a proxy for pig health. We included meat inspection findings in 10.5 million finishers delivered to 9 Danish abattoirs between 2016 and 2020 from herds classified as having a low, medium, or high AMU (Yellow Card herds). The prevalence of meat inspection findings was calculated and analysed in mixed-effects logistic regression models to determine the associations between each of eight selected lesions and AMU level while also considering the effect of herd size, location (east or west) and herd type (indoor or outdoor). Despite differences in AMU, only minor differences in meat inspection lesions were present. The overall result of the multivariable modelling was that herds with a medium AMU level were associated with the lowest prevalence of meat inspection lesions - observed for five out of the eight lesions investigated. Moreover, large herds were associated with a lower prevalence of meat inspection lesions than small herds - observed for seven out of eight lesions. The prevalence of lung and tail lesions was higher for herds in the western region of Denmark compared to the eastern regions, and the prevalence of tail lesions, arthritis and osteomyelitis was higher in outdoor herds compared to indoor herds. Hence, both a high and a low AMU could be linked with health and welfare issues. The results indicate that the advisory role of the herd veterinarian is pivotal in preventing adverse effects of antimicrobial reduction measures on animal health and welfare, in particular, if the Yellow Card limits are reduced further.