Metabolic Profile Reference Intervals Across Physiological Periods and Parity in Holstein Dairy Cows

Reference intervals established according to physiological and environmental variables are required for the accurate interpretation of clinical blood results. Most reference intervals for Holstein dairy cows are based on limited sample sizes or cover only specific physiological periods. This study aimed to establish reference intervals for metabolic profile analytes across all physiological periods of the production cycle in Holstein dairy cows and to evaluate the effect of parity on the analytes. From 91 dairy farms located in the Küçük Menderes Basin of İzmir Province, a total of 2562 cows that met the inclusion criteria were enrolled. The cows were in the dry, close-up, fresh, mid-lactation, or late-lactation periods. Analyses were performed using a Biosystems BA-200 Vet wet chemistry automated analyzer. Calculations were performed using nonparametric methods (median and 2.5th and 97.5th percentiles) in accordance with the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Veterinary Clinical Pathology (ASVCP) guidelines. The need for partitioning was assessed using the Harris-Boyd z-test. All analytes differed significantly among physiological periods (p < 0.001). All analytes differed significantly among physiological periods (p < 0.001). The confidence intervals for the reference limits were relatively narrow, and parity-related differences were observed for several analytes, especially alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and total protein (TP), within some physiological periods. As a result, the reference intervals established in this study will provide a reliable guide for clinical diagnosis and herd health management in dairy cattle medicine. Additionally, our results demonstrate that, when interpreting blood results in Holstein dairy cows, reference intervals should be specific to the physiological period and, for certain analytes, stratified by parity.