Treatment of clinical mastitis (CM) and use of antimicrobials for dry cow therapy are responsible for the majority of animal-defined daily doses of antimicrobial use (AMU) on dairy farms. However, advancements made in the last decade have enabled excluding nonsevere CM cases from antimicrobial treatment that have a high probability of cure without antimicrobials (no bacterial causes or gram-negative, excluding Klebsiella spp.) and cases with a low bacteriological cure rate (chronic cases). These advancements include availability of rapid diagnostic tests and improved udder health management practices, which reduced the incidence and infection pressure of contagious CM pathogens. This review informed an evidence-based protocol for selective CM treatment decisions based on a combination of rapid diagnostic test results, review of somatic cell count and CM records, and elucidated consequences in terms of udder health, AMU, and farm economics. Relatively fast identification of the causative agent is the most important factor in selective CM treatment protocols. Many reported studies did not indicate detrimental udder health consequences (e.g., reduced clinical or bacteriological cures, increased somatic cell count, increased culling rate, or increased recurrence of CM later in lactation) after initiating selective CM treatment protocols using on-farm testing. The magnitude of AMU reduction following a selective CM treatment protocol implementation depended on the causal pathogen distribution and protocol characteristics. Uptake of selective treatment of nonsevere CM cases differs across regions and is dependent on management systems and adoption of udder health programs. No economic losses or animal welfare issues are expected when adopting a selective versus blanket CM treatment protocol. Therefore, selective CM treatment of nonsevere cases can be a practical tool to aid AMU reduction on dairy farms.

To counteract the globally increasing threat of antimicrobial resistance, antimicrobials should be used prudently, both in humans and in animals. A general principle of prudent antimicrobial use in veterinary medicine is that animals receive antimicrobials appropriate to their clinical needs, and while the efficacy of these antimicrobials for treating animals and humans is sustained (Weese et al., 2013; OIE World Organization for Animal Health, 2016). This requires that prophylactic and growth promoting antimicrobial use practices should be abandoned and antimicrobial treatments should be diminished by minimizing the incidence of infectious diseases. When antimicrobial treatments are used to treat a bacterial infection, they should be carefully selected and administered based on prudent use principles (Weese et al., 2013; Aarestrup, 2015; Speksnijder et al., 2015a, Speksnijder et al., 2015b and Speksnijder et al., 2015c). The recently published WHO-Guideline aligns with these principles (Aidara-Kane et al., 2018) and suggest the need for measures that are partly dependent on the development and enforcement of regulations (e.g., stop the use of growth promotors). When it comes to on-farm decisions for treatment, behavioral aspects are as important as technical ones. Aspects like prior experience and risk avoidance have a major influence on the decision about treatment. Typically, farmers and veterinarians are responsible for implementing disease preventive measures and for prescribing and/or administering antimicrobials. There is extensive knowledge available to substantially prevent, reduce, and control the burden of many animal diseases without the use of antimicrobials in production animals; the battleground is in consistently and effectively implementing the necessary management changes (LeBlanc et al., 2006; Ruston et al., 2016). The adoption of prudent antimicrobial use principles thus requires a behavioral change in veterinarians and farmers. It is widely believed that the role of veterinarians should change from reactive and curative antimicrobial prescribers toward a more proactive role as animal health consultants for farmers, without relying on prescribing antimicrobials. Farmers should ideally depart from relying on using antimicrobials as a management tool toward a more proactive approach that prevents animal diseases, and uses antimicrobials only as a last resort (i.e., when preventive measures have failed). In practice, however, these behavioral changes seem rather difficult to accomplish (Garforth, 2015; Speksnijder et al., 2015a, b). The reasons why behavioral changes are often difficult to initiate and sustain in practice are complex and typically differ from person to person. The use of sociopsychological models might help to better understand the different factors that influence current behaviors and how to invoke behavioral changes in farmers and veterinarians related to antimicrobial use practices and the uptake of preventive measures. Insights into enabling or inhibiting factors can be helpful for policy makers, advisers, and others, which will ultimately help support veterinarians and farmers in adopting new behaviors (Kristensen and Jakobsen, 2011; Garforth, 2015).