Use of on-farm culturing for clinical mastitis treatment decisions and antimicrobial use in Argentina

Clinical mastitis (CM) is one of the main causes of antimicrobial use (AMU) in dairy cattle, and strategies that support selective therapy are essential to promote responsible antimicrobial stewardship. This study evaluated the use of a commercial on-farm culture (OFC) system supported by an artificial intelligence-based mobile application to describe pathogen prevalence, assess AMU, and characterize treatment practices on dairy farms in Argentina. A retrospective longitudinal study was conducted using data generated between April 2022 and June 2025 from dairy farms implementing the OFC system. Only new mild and moderate CM cases were included in the analysis. Microbiological diagnoses and antimicrobial treatments administered via intramammary and/or parenteral routes were descriptively analyzed. A total of 26546 CM were evaluated. No bacterial growth was the most frequent diagnosis, followed by non-aureus staphylococci, Staphylococcus aureus, environmental streptococci, and Gram-negative bacteria. Overall, approximately half of the cases did not receive antimicrobial treatment. When antimicrobials were used, intramammary administration was the most common route, although parenteral treatments were still applied in a considerable proportion of mild and moderate cases. Critically important antimicrobial groups (macrolides and aminoglycosides) were frequently used for intramammary therapy, and combined antimicrobial formulations predominated. The implementation of OFC provided relevant microbiological information to support therapeutic decision-making and contributed to a substantial reduction in AMU. Strengthening collaboration between farmers and veterinarians is essential to improve antimicrobial stewardship and align mastitis treatment practices with microbiological evidence and international recommendations.