Reference Intervals of Selected Serum and Plasma Biochemical Analytes in Clinically Healthy Multiparous Holstein Cows During the Periparturient Period

Background: Monitoring the metabolic changes during the periparturient period is crucial. Objective: We aimed to establish reference intervals (RIs) of several serum and plasma biochemical variables in multiparous periparturient Holstein dairy cows. Methods: A total of 238 multiparous dry cows from six commercial dairy farms were enrolled. Blood samples were collected at predetermined time points (21 and 7 days before the expected calving date, 7, 21, and 28 days after calving, ±2 days on all occasions). Samples from 113 cows that met the inclusion criteria were analyzed for plasma and serum biochemical analytes. Results: The lower and upper reference limits were 40.9–49.3 and 102.8–128.5 U/L, respectively, for aspartate aminotransferase; 9.1–14.0 and 33.8–47.8 U/L for γ-glutamyl transferase; 0.07–0.13 and 0.20–0.43 mmol/L for triglycerides; 1.11–1.25 and 3.04–3.52 mmol/L for cholesterol; 0.0 and 3.42–7.78 μmol/L for total bilirubin; 141.0–285.0 and 778.6–1279.3 μmol/L for β-hydroxybutyrate, 0.07–0.22 and 0.42–1.24 mmol/L for non-esterified fatty acids; 50.8–59.7 and 77.4–103.5 g/L for total protein; 23.6–29.2 and 39.4–48.5 g/L for albumin; 19.4–28.3 and 42.0–58.3 g/L for globulin; 0.59–0.70 and 1.30–1.61 for albumin/globulin ratio; 1.3–3.2 and 7.6–9.7 mmol/L for blood urea nitrogen; 42.4–62.8 and 83.1–124.7 μmol/L for creatinine; 1.8–3.2 and 9.8–25.1 μmol/L for 3-methylhistidine; and 1.9–2.7 and 10.5–14.8 μmol/L for 1-methylhistidine. Conclusions: The established RIs provide valuable benchmarks with important clinical and research applications in dairy cattle medicine.