Enhancing antimicrobial stewardship on dairy farms with a focus on selective treatment of clinical mastitis
Clinical mastitis treatment decisions have been the focus of antimicrobial stewardship in the dairy sector, as clinical mastitis and antimicrobial dry cow treatments account for most antimicrobials used on farms. To improve on-farm antimicrobial stewardship, this thesis focusses on selective treatment of clinical mastitis, which center around milk culture-guided decisions.
In essence, a selective treatment protocol aims to identify clinical mastitis cases that benefit from antibiotic treatment. Prior to initiating treatment, it is recommended to analyze a milk sample from the affected quarter. If the culture indicates no bacterial growth or if gram-negative bacteria are cultured, antibiotics are unnecessary. This protocol can lead to a substantial reduction in antibiotic use, especially on farms where most clinical mastitis cases are caused by gram-negative bacteria. An evaluation of over a dozen clinical trials conducted the past decade confirms that such a treatment protocol, based on milk culture outcomes, does not impact bacteriological and clinical cure, somatic cell count, milk yield, and incidence of recurrence or culling. No negative economical consequences were identified. In addition, findings from a nationwide survey demonstrated an increased adoption of selective CM protocols among farms with a low average cow SCC. This suggests that farms with better udder health are inclined to use selective treatment approaches.
To facilitate the implementation of selective treatment protocols on dairy farms, it is crucial to understand the decision-making process. Interviews with 15 Canadian diary farmers resulted in a detailed description of the steps and factors considered, such as the evaluation of milk production and quality data, value of the cow, herd goals, urgency of treatment, available drugs, and timing of the case. The shared decision-making dynamics among farmers, veterinarians and milkers were also highlighted as key factors impacting treatment decisions. Importantly, the interviews revealed that most treatment decisions are made intuitively, favoring choices geared toward short-term gains. Therefore, interventions should focus on slowing down the decision-making process to incorporate new steps, such as milk culturing, which result in long-term gains, namely, reducing antibiotic use.
Subsequent discussions led to ten proposed interventions that address voiced barriers to culture-guided treatment decisions and appeal to motivators. These interventions include training to improve aseptic sampling, education to improve interpretation of test results and increase problem awareness, offering of comprehensive udder health packages that include milk sampling to enable farmers to send in samples, persuasion through veterinarians and farm magazines to adopt milk culturing, increasing social acceptance through demonstration farms and peer study groups, and lastly, incentivize farmers to adopt culturing through benchmarking. Implementing these interventions can lead to an increased uptake of selective CM treatment protocols.
If you are interested in implementing a selective clinical mastitis treatment protocol on your farm, reach out to your herd veterinarian or your local udder health specialists.
Dr. Ellen de Jong recently received her PhD in Veterinary Epidemiology from the Faculty of Veterinary Medicine at University of Calgary in Canada. Before this, she completed her BSc and MSc Animal Sciences at Wageningen University in the Netherlands. Ellen is currently working with cow-calf producers in her role as postdoctoral researcher at University of Calgary, Canada.
