Intramammary bacterial profile and its impact on the number and differential distribution of somatic cells in the context of drying off in dairy cows

Mastitis remains one of the most significant conditions in dairy cattle farms, with major consequences for animal health and milk quality. The aim of this study was to determine the prevalence of intramammary infections (IMI) and to analyze the relationship between the pathogens involved, the total somatic cell count (SCC), and their differential distribution (DSCC) in two family-owned farms of Romanian Spotted cows, evaluated before and after drying-off. A total of 140 milk samples were collected and analyzed using standard microbiological examinations, as well as SCC and DSCC determinations by flow cytometry. The results revealed an overall IMI prevalence of 32.9%, with differences between the two farms: in Farm 1, major pathogens predominated (Streptococcus agalactiae, S. uberis, S. dysgalactiae, Escherichia coli), whereas in Farm 2, minor pathogens were more frequently isolated (coagulase-negative staphylococci, Corynebacterium spp.). The mean SCC value was significantly higher in positive samples (807,557 cells/mL) compared to negative samples (98,243 cells/mL), with the highest values associated with E. coli infections. Similarly, DSCC showed marked differences between uninfected (26.2%) and positive samples (68.4%), with a tentative threshold of 65% suggested as indicative of intramammary infection. The results confirm the utility of combining SCC and DSCC for more accurate mastitis detection and highlight the importance of pathogen characterization at the farm level to optimize management strategies and apply selective therapy at drying-off.