Innovating antimicrobial stewardship on dairy farms through on-practice culture
Antimicrobial resistance (AMR) is widely recognized as a major One Health challenge, affecting both human and veterinary medicine. In the dairy sector, mastitis remains the leading cause of antimicrobial use (AMU), making improved udder health management essential for reducing unnecessary treatments while safeguarding animal welfare and milk quality. In the dairy sector, selective strategies such as selective dry cow therapy (SDCT) and selective treatment of non-severe clinical mastitis (STCM) are central to transition towards more preventive, diagnostic-driven practices. In this context, Lien Creytens conducted her doctoral research regarding innovating antimicrobial stewardship on Belgian dairy farms (Flemish region).
Results from the systematic review showed that STCM was not inferior to immediate antimicrobial treatment with respect to bacteriological and clinical cure, somatic cell count, milk production, recurrence, or culling. The overall quality of evidence ranged from moderate to high, supporting the safe and effective adoption of STCM as part of mastitis management strategies.
The central experimental component of the thesis was a two-year randomized clinical field trial involving 11 veterinary practices and 34 commercial dairy farms. Selective treatment was evaluated using an on-practice culturing approach, particularly relevant in Flanders where farms are geographically close to veterinary practices. The study demonstrated that STCM did not negatively affect bacteriological and clinical cure, nor somatic cell count. Moreover, the duration of days milk out of tank was significantly shorter when STCM was applied. Although milk production was lower when STCM was applied, this effect was limited to herds with suboptimal udder health and was unrelated to antimicrobial treatment. Overall, 42.8% less cows received antimicrobial treatment when STCM was applied compared with immediate antimicrobial treatment, with the greatest impact observed in well-managed herds.
Recognizing that antimicrobial stewardship requires both veterinary leadership and informed decision-making by dairy producers, dairy producers and bovine veterinarians were questioned regarding their knowledge, attitudes, opinions and practices regarding udder health. Among the dairy producers, substantial knowledge gaps emerged: 75% was unable to distinguish clinical from subclinical mastitis. Although most respondents valued veterinary herd health monitoring, routine milk sampling remained uncommon. While 88% expressed openness to new treatment strategies, fewer than half had implemented SDCT, and only 60% showed strong interest in bacteriological culturing of milk through RTS. Producers who participated more frequently in veterinary herd health programs demonstrated better knowledge and more favorable attitudes. Among the bovine veterinarians, 92.5% highly valued herd health monitoring, however, both the frequency and content of these services could be improved. Younger veterinarians showed greater awareness of AMU, AMR, and the importance of bacteriological culturing than their more experienced colleagues. The findings highlighted the need for continued education and structural support to strengthen veterinary competencies in evidence-based mastitis management.
Finally, two RTS were evaluated under on-practice conditions. Both tests reliably distinguished Gram-positive from Gram-negative pathogens, supporting their use in selective treatment decisions, although their ability to identify specific pathogens was limited.
In conclusion, STCM is a valuable strategy for reducing AMU, but only when embedded within strong udder health management, veterinary guidance, adequate diagnostics, and supportive policies. Sustainable antimicrobial stewardship requires aligned incentives, responsibilities, and competencies across all stakeholders.
Lien Creytens grew up on a dairy farm, where she developed a strong interest in animal health and welfare. In 2017, she graduated as a veterinarian, with a focus on ruminants. She subsequently gained professional experience as a bovine veterinarian and worked in both companion animal practice and the veal calf sector. In October 2021, she began her doctoral research within the M-team at Ghent University under the supervision of Sarne De Vliegher and Sofie Piepers, with support from VLAIO. She successfully defended her PhD on March 31, 2026.
