Gene Expression in Circulating Leukocytes in Brown Swiss and Holstein Cows During the Transition Period

The transition period is characterized by major metabolic and immunological changes that increase disease susceptibility in dairy cows. Genetic background may influence the regulation of immune responses during this phase. The aim of this study was to compare the expression of immune-related genes in circulating leukocytes of Brown Swiss and Holstein cows across the transition period. Twenty-two pregnant heifers (10 Brown Swiss and 12 Holstein) were managed under identical conditions and sampled at −21, +7, and +28 days relative to calving. Whole blood was collected using PAXgene tubes, and gene expression was analyzed by quantitative PCR. Target genes were associated with immune recognition, leukocyte migration and adhesion, antimicrobial activity, oxidative stress, and inflammatory response. Gene expression profiles differed between breeds over time. Holstein cows showed higher expression of genes involved in pathogen recognition before calving, including CD14 and TLR4. In contrast, Brown Swiss cows showed higher expression of genes related to leukocyte migration (ITGAL, CCR2), antimicrobial activity (MMP9, MPO), inflammatory response (TNFA, IL18), and oxidative stress (ALOX5, ALOX15), particularly after calving. These results indicate breed-related differences in leukocyte gene expression and suggest that genetic background influences immune adaptation during the transition period.