Different European Perspectives on the Treatment of Subclinical Mastitis in Dairy Cows

As part of the European Network for Optimization of Veterinary Antimicrobial Treatment (ENOVAT), a webinar on the topic “Different European Perspectives on the Treatment of Subclinical Mastitis in Lactation” was held on September 21, 2022, during which eight mastitis experts from different European countries (France, Hungary, Italy, the Netherlands, Portugal, Slovenia, Sweden, and the United Kingdom) presented their treat- ment approaches for subclinical mastitis during lactation. The information provided by the experts is based on experience, guidelines, surveys, and opinions of the university to which they belong. The aim of this study was to compare the therapeutic approaches to identify commonalities and differences. It was not the aim of the webinar to identify the best approach for the treatment of subclinical mastitis, but to better understand the different approaches in the different countries in order to find starting points for long-term harmonization. The definition of subclinical mastitis varies from country to country. However, in all countries the definition is based on the presence of increased somatic cell count (SCC) in the quarter milk but without clinical signs or visual changes in the milk and is usually caused by an intramammary infection (IMI). Particularly regarding the cell count limit, the definitions differ between countries. In all participating countries, treatment of subclinical mastitis is not standard practice. This varies from a general rejection of treatment during lactation to treatment in special situations, involving the risk of penalties if a certain threshold of cells in the bulk tank milk is exceeded. Diagnostically, in its simplest form, subclinical mastitis in cows is determined by an individual cow SCC being greater than a threshold. The SCC numbers are most commonly received via regular monthly dairy herd milk recording (DHI). It was reported that the importance of bacteriological analyses has increased significantly, leading to more targeted interventions. Whether a cow is treated or classified as unworthy of treatment depends on various factors such as age, fertility, pathogens present, and duration of intramammary infection (chronicity) based on DHI data and other criteria. It was reported that in some countries a trend over the past ten years is evident showing a decrease in treatment frequency and a concomitant decrease in antibiotic use, while the use of alternative agents, often non-evidence-based, is increasing. At the same time, no increase in the bulk milk somatic cell count (BMSCC) is evident but rather BMSCC continues to decrease despite the reduced use of antibiotics and increased use of alternative agents implying better cow management. The aim of the Enovat project on mastitis therapy is to produce evidence-based guidelines. The collection of expert opinions is an essential step towards a better understanding of mastitis therapy in different European countries, especially in the absence of common guidelines. Unfortunately, the quality of databases in European countries on the use of antibiotics in mastitis therapy is still rather imprecise. Therefore, to understand the practices and make them more evidence-based in the long run, it is even more important to hear the opinions of key opinion leaders. In principle, there is common ground and consensus on certain points of treatment. For example, treatment is generally considered appropriate only after bac- teriological diagnosis. However, the results of the webinar show that there are still differences in the definition and treatment of subclinical mastitis. Only through exchange and communication, a reasonable guideline for the treatment of subclinical mastitis can be found. The exchange could generate important research questions. Answering these questions could contribute to the development of common evidence-based guidelines.