The relationship between antimicrobial use and somatic cell counts (SCC) in dairy cows has been described in the literature on multiple occasions [1, 2]. Results from the research project “Relationship between Antimicrobial Use, Management, and Animal Health Indicators” (1.22.02) also demonstrated an association between antimicrobial use (AMU) and specific animal health indicators in dairy cows. Farms with a higher treatment index (TBI) showed, among other findings, a trend toward lower bulk tank somatic cell counts. However, it remains unclear to what extent milk quality thresholds and premium payment systems influence the SCC of delivered milk and the use of intramammary antimicrobials.
According to the requirements of the Ordinance on Hygiene in Milk Production (VHyMP), milk from each supplying dairy farm is tested twice monthly as part of the official public milk testing program, based on three criteria: total bacterial count (“Keimzahl”) as an indicator of hygiene (threshold <80,000 CFU/mL), somatic cell count (“Zellzahl”) as an indicator of udder health (threshold <350,000 cells/mL), and the presence of inhibitory substances (”Hemmstoffe”) as an indicator of veterinary drug residues (sample must test negative).
In addition to public regulatory testing, there is also a private-sector milk quality control system in which producer and processor organizations have established standardized rules for quality-based milk payment (“Regelung der Milchbranche für Kuhmilch”) [3]. This system defines both deductions and quality premiums. While the deductions are aligned with the regulatory thresholds, stricter criteria apply for receiving a quality premium. For processing milk (“Molkereimilch”), this premium is granted when SCC is below 100,000 cells/mL, provided the milk also meets requirements for bacterial count, absence of inhibitory substances, and freezing point. For milk used for cheese production, it is recommended that the premium be aligned with the specific requirements for silage-free milk production.
This raises the question of whether financial incentives lead producers to maintain SCC below the industry-defined threshold of 100,000 cells/mL, and whether intramammary antimicrobials are increasingly used to achieve this target. This issue is particularly relevant in the context of the global concern over the relationship between antimicrobial use and the emergence of antimicrobial resistance. Furthermore, it remains unclear to what extent the SCC of delivered milk (Bulk Tank Milk Somatic Cell Count, BTMSCC) reflects the actual average SCC of the herd, and thus how suitable it is as an indicator of udder health at the farm level (and how well findings from other countries can be applied to the Swiss context, given the differences in threshold values [4]).
