Hematologic values in calves during the first 6 months of life

Background: Age‐related changes in hematologic values are known to occur in many species. Few published studies include repeated measurements of hematologic parameters in calves during the first months of life. Objective: The aim of the present study was to monitor hematologic values by sequential measurements from birth to 6 months of age in 15 healthy calves of the Norwegian Red breed, and compare the results to reference intervals for adult, lactating dairy cows. Methods: Fifteen clinically healthy calves were sampled every week during the first 5 weeks of life and every month thereafter until 6 months of age. Hematologic values were measured using the ADVIA 120 hematology system. Reference intervals were determined for 75 healthy adult cows of the same breed. Results: Compared with adult reference intervals, the MCV was lower and the RBC count was higher in calves throughout the investigation period. Hemoglobin concentration stayed largely within the adult reference interval. Mean MCHC was lower than adult values for 5 weeks, then increased and reached adult values by weeks 10–12. The mean lymphocyte count for calves reached adult reference values at weeks 6–8, and the mean monocyte count increased steadily until weeks 14–16. For most leukocytes, interindividual variation was larger during the first 5–8 weeks of life. The mean platelet count for calves was higher than the adult reference interval until weeks 19–21 of age. Conclusions: Age‐specific reference intervals for calves from birth to 6 month of age are needed for RBC count, MCV, MCHC, red cell distribution width, and platelet and lymphocyte counts.