PHAGOCYTOSIS AND PRODUCTION OF REACTIVE OXYGEN SPECIES (ROS) BY CH138+ GRANULOCYTES ISOLATED FROM BLOOD, COLOSTRUM AND TRANSITION MILK OF HOLSTEIN COWS

This study investigated the functional activity of CH138+ granulocytes in blood, colostrum, and transitional milk from Holstein cows throughout the transition period. Thirteen cows were assessed weekly, beginning three weeks before calving (W-3, W-2, W-1), on the day of calving, and continuing to three weeks postpartum (W1, W2, W3). Physical examinations of udder tissue, bacterial cultures, and blood immune function tests were performed. Microscopic Somatic Cell Count (MSCC), phagocytosis, and intracellular ROS production by CH138+ granulocytes in colostrum and transitional milk were measured weekly from calving to W3. Disease incidence was recorded, with four cows developing metritis at W2. Mammary gland edema, affecting parenchymal tissue consistency, was the main physical finding. Non-Aureus Staphylococcus spp. dominated bacterial isolates from mammary secretions (67.5%). MSCC was highest in colostrum, then decreased postpartum. Bacterial culture rates peaked at calving; however, colostrogenesis limited clinical mastitis detection through specific examinations. Blood neutrophil function decreased at W-2 and W-1, likely increasing mammary infection risk and weakening neutrophil response at calving. This immune suppression, affecting both the mammary gland and systemic immunity, was exacerbated by postpartum metritis. Findings showed heightened vulnerability to bacterial infection postpartum, linked to reduced cell viability and CH138+ granulocyte function. Neutrophil function in mammary secretions gradually improved post-calving, supporting immune recovery and a decline in infection rates. The findings provided valuable insights into the immune adaptations of CH138+ granulocytes in colostrum and transitional milk, enhancing understanding of mammary and systemic immune response during the transition period.