Open Access

Volker Krömker, Ulrike Falkenberg, Nicole Wente, Yanchao Zhang, Stefanie Leimbach, Julia Nitz, Philippe Gisbert, Franziska Nankemann

• Targeted mastitis treatment concepts are the most scientifically validated approaches to comply with the prudent use of antimicrobials. However, this approach is still a challenge for many farmers, who often lack experience with it. Another option for more prudent use of antibiotics in mastitis therapy could be the initial treatment with a nonsteroidal anti-inflammatory drug (NSAID) for nonsevere mastitis. A randomized, multiherd, noninferiority study was carried out to compare 2 treatments of nonsevere mastitis cases. The animals in the studied group were treated with systemic NSAID (ketoprofen [KE]; KE group; n = 104), followed by antibiotic (AB) treatment only in cases without clinical improvement, and the animals in the reference group (AB group) received an intramammary AB (n = 118). The study included 222 cases of nonsevere clinical mastitis on 3 conventional dairy farms in northern Germany between November 2022 and November 2023. Study outcomes were clinical cure at d 5, bacteriological cure, clinical mastitis recurrence in a period of 60 d, and new infection risk. Mixed logistic regression was used to analyze the effect of treatment on outcomes. The noninferiority assumption was checked with the CI of the treatment difference for clinical cure at d 5, calculating using the LSM and their SD. With regard to the clinical cure on d 5, the treatment in the KE group was inferior. Clinical cure (84.7% [100/118] and 61.5% [64/104]) and bacteriological cure (79.3% [73/92] and 61.2% [41/67]) were significantly higher in the AB group than in the KE group. The risks for recurrent cases (7.3% [8/109] and 15.7% [14/89]) were significantly lower in the AB group than in the KE group. The new infection risk did not differ significantly between the treatment groups (6.8% [8/118] in the AB group and 6.7% [7/104] in the KE group). In 87% of the cases (n = 90) of the KE group, a subsequent antibiotic treatment was not necessary to reach clinical cure on d 5. The use of KE as the sole initial treatment for nonsevere mastitis led to a reduction of antibiotic doses by 86%. Our findings revealed that systemic treatment with KE resulted in lower clinical and bacteriological cure rates, higher recurrence rates of clinical mastitis, and an elevated risk of new infections compared with the antibiotic-treated group. Nevertheless, in more than 85% of cases treated with KE, additional intramammary antibiotic treatment was unnecessary. Thus, this treatment concept represents an alternative in mastitis treatment that promoted the deliberate and selective use of antibiotics but has limitations in terms of treatment efficacy in mastitis. A targeted mastitis concept based on the identification of the bacterium involved could help to select cases to be treated with KE alone and therefore overcome this limitation.