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.