Hematological Changes and Reference Intervals in Hanwoo Calves during the First 28 Weeks of Life

SIMPLE SUMMARY: Complete blood cell count is important in identifying diseases in animals, and reference intervals must be established considering physiologic differences in genotype, age, sex, and management. However, little research has been performed to evaluate complete blood cell count reference intervals in Hanwoo calves. Therefore, we compared the complete blood cell count reference intervals of Hanwoo cows and Hanwoo calves and examined changes in calves’ complete blood cell count from birth to 28 weeks. We confirmed that complete blood cell count reference intervals specifically for calves are necessary for accurate diagnosis of calf diseases. In addition, the difference in complete blood cell count between female calves and male calves was confirmed for only some ages and some parameters. Our results suggest that reference intervals for Hanwoo calf complete blood cell count are necessary for accurate diagnosis of calf diseases ABSTRACT: Hematological reference intervals must consider several parameters, including genotype, age, sex, management, and analytic process. Work is needed to evaluate hematological changes specifically in Hanwoo calves and according to calf sex. Therefore, in this study, we sought to confirm the complete blood cell count (CBC) reference intervals in Hanwoo calves, to monitor changes in hematologic values in Hanwoo calves from birth until 28 weeks of life, and to compare the hematologic values of male and female calves. A total of 35 male calves and 35 female calves was studied. Calf blood was sampled at multiple intervals from the time of birth until 28 weeks of age (including within 6 h of birth and at 2 days, 7 days, and 4 weeks and then at 4-week intervals through 28 weeks). In addition, blood samples were collected from 210 clinically healthy pregnant Hanwoo cows to establish CBC reference intervals for adult cattle. There were significant differences in the results of the cows and calves in all 14 parameters considered. The CBC reference intervals of the calves were wider than those of the cows in all parameters except mean corpuscular volume, mean corpuscular hemoglobin concentration, and mean platelet volume. We also identified differences from birth through 28 weeks between male and female calves at only some ages and some parameters. These results suggest that CBC reference intervals specific to Hanwoo calves are necessary for accurate diagnosis of calf diseases.