Association of intramammary infection status with energy balance and immune function during peripartum in dairy cows

Abstract

This observational study evaluated whether intramammary infection (IMI) status was associated with energy balance and immune system indicators during the peripartum period in clinically healthy grazing dairy cows (n =24). Body condition score (BCS) was assessed and blood samples were collected at 52 and 15 days prepartum and at 3, 10, 26, and 47 days postpartum to determine serum concentrations of nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHB), total protein, albumin, globulins, cholesterol, haptoglobin and total and differential white blood cell (WBC) counts in whole blood. Gene expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in peripheral leukocytes were also measured at 51 and 15 days prepartum and at 12 days postpartum. Cows were classified as IMI-positive (n = 15) if at least one pathogen was isolated from any quarter at 7 days postpartum, and as IMI-negative (n = 9) if no bacterial growth was observed in any of the four quarter samples. Associations between IMI status and response variables were evaluated using mixed linear regression models with repeated measures. Cows with IMI showed a more pronounced and prolonged BCS loss, along with higher NEFA concentrations at 10 days postpartum, suggesting greater lipid mobilization. At the same point, the IMI-positive group had significantly higher serum total protein and albumin concentrations. Haptoglobin concentration was higher in the IMI-positive group, indicating an acute phase response. The IMI-positive group exhibited greater total WBC counts and a trend for increased neutrophil and lymphocyte counts. No significant differences were observed for the remaining metabolic variables and cytokine gene expression markers evaluated. In conclusion, differences in lactational adaptation and immune-related parameters were observed between clinically healthy cows with and without IMI during the peripartum period.