Risk factors for antimicrobial usage and diseases in Dutch veal calf farms: A cross-sectional study

Antimicrobial use (AMU) is the main driver of antimicrobial resistance (AMR). In the Netherlands, the veal calf sector was among the largest consumers of antimicrobials in Defined Daily Doses Animal (DDDA) for the year of 2022. As preventive use in Dutch livestock farms is forbidden since 2011, most AMU is due to the herd health status which is affected by the farm environment in which the conditions for diseases to spread are created. The aim of this study was to determine which disease etiologies for group treatments are associated with AMU in rosé starter veal calves, and which modifiable technical risk factors on farm are associated with those diseases and with total AMU. Cross-sectional data were collected from 36 Dutch rosé starter veal calf farms in the Netherlands in 2021 using a digital survey. Linear regression analysis showed that the main indications for AMU were respiratory infections, for which mainly tetracyclines and macrolides were used. Partial least squares regression analysis (PLS) revealed 13 on-farm practices associated with the number of group treatments for respiratory diseases and 19 with total AMU. Overlapping variables in both PLS models were related to regrouping of calves, micro-climate conditions, water access and weaning strategies. Overall, these features focused on improving animal welfare and nutrition during production and enhancing a farm's internal and external biosecurity. This study identified opportunities for reducing AMU in rosé starter veal calf farms, which thereby could contribute to limiting AMR emergence and spread.