Observational Study on Antimicrobial Treatment Frequencies and Culling Rates in a Cohort of Dairy Herds in Lodi Province (Italy)

In recent years, there have been important regulatory and management changes in livestock farming in Italy and other European countries. The goal of these changes has been to decrease the use of antimicrobials (antimicrobial stewardship). The objective of this observational study was to explore the potential relationship between the decrease in the use of antimicrobials and the rise in the culling of dairy cattle on 210 farms in the Lodi province. Records of antimicrobials used in dairy herds (measured as the daily defined dose animal for Italy-DDDAit) and culling rates were retrieved from the Italian Ministry of Health official databases. These were statistically analyzed to assess the presence of an association between changes in the DDDAit and changes in the culling rates in 2023 and 2024. The results indicated that the DDDAit exhibited minimal fluctuations over the two-year period (3.61% vs. 2.45%). However, there was a notable shift observed in the culling rates, particularly among smaller herds (24.51 vs. 39.27%). The statistical analysis showed a significant correlation between herd size and antimicrobial treatment, with a higher frequency in larger herds. The results of this study indicate that reducing antimicrobial treatments alone may not necessarily result in better animal welfare or herd sustainability, particularly when it is associated with an increase in the culling rate. It also suggests that antimicrobial treatment rates and culling rates derived from a mandatory recording system provide a simple means of verifying the level of herd health management and of assessing the antimicrobial stewardship approach efficacy.