Changes in biomarkers of nutrient metabolism, inflammation, and oxidative stress in dairy cows during the transition into the early dry period.

Metabolic stress occurs in dairy cows when physiologic homeostasis is disrupted as a consequence of aberrant nutrient metabolism, chronic inflammation, and oxidative stress. Early-lactation cows that suffer from metabolic stress are susceptible to health disorders that cause significant production losses. However, there is little information regarding the occurrence and effect of metabolic stress during involution. Therefore, the purpose of this study was to investigate well-known biomarkers associated with metabolic stress in early-lactation cows at various time points during the early dry period when dairy cows also are subjected to dramatic changes in physiologic homeostasis. Our group conducted a descriptive study by collecting serum and whole-blood samples from the coccygeal vein of 29 healthy dairy cows at a commercial dairy herd. Sampling points included d -6, 0, +1, +2, +6, and +12 relative to dry-off date. Samples were used to quantify biomarkers related to nutrient metabolism, oxidative stress, and inflammation that included calcium, nonesterified fatty acids, β-hydroxybutyrate, albumin, haptoglobin, cortisol, reactive oxygen and nitrogen species, antioxidant potential, oxidant status index, and isoprostanes. Additionally, whole-blood leukocyte differentials for total leukocyte, neutrophils, lymphocytes, eosinophils, and monocytes were analyzed. Within altered nutrient metabolism biomarkers, calcium and nonesterified fatty acid concentrations changed most from d 0 to d +2 during the sampling period. Indicators of oxidant status, such as reactive oxygen and nitrogen species, antioxidant potential, and oxidant status index, generally increased throughout the sampling period except at d +2, suggesting altered redox status throughout early involution. In contrast, isoprostane concentrations fluctuated throughout the study, demonstrating that indicators of oxidative damage occurred more sporadically during the sampling period. Therefore, many of the biomarkers associated with early-lactation metabolic stress also changed during the transition from late lactation to the early dry period, but not to the same magnitude and duration previously reported in periparturient cows. Future studies should be directed toward assessing whether the magnitude and duration of biomarker expression can affect the health and well-being of cows during the early dry period.