Hematological investigations in calves during the first week of life in East German dairy herds While the etiology, pathogenesis and therapy of iron deficiency anemia are well understood, the causes of congenital anemia have not been elucidated in detail. The literature lists impaired fetal erythropoiesis due to inadequate placental iron-transport as a cause. Another possible cause is fetal blood loss around birth. The aim of the present study was to investigate hematological parameters of calves in the first week of life regarding the prevalence of congenital anemia on East German dairy farms. In addition, the dynamics of blood parameters were to be illuminated and factors influencing the initial blood parameters of the calf were to be characterized. For this purpose, two investigations were conducted. In investigation 1 (US1), a large dairy farm in northern Brandenburg was visited regularly between October 2016 and September 2017 in order to study a large test population under the same housing and management conditions. In study 2 (US2), 5-12 calves were sampled at the first week of life on 30 different farms. Mean values were compared and the prevalence of congenital anemia calculated. Investigations especially focused on the hematocrit. Furthermore, the blood parameters hemoglobin, erythrocyte count (RBC), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), platelets and leukocytes were determined. To examine associations and influencing factors, categorical variables were compared using ANOVA with post-hoc tests. Metric variables were modeled with blood parameters in a regression analysis. In US2, the influences of selected ingredients of the Total mixed rations (TMR) fed to the transition cows on calf blood parameters were additionally evaluated using multiple regression models. Hematocrit reference intervals ranged from 0.164-0.417 l/l in US1 and from 0.175-0.455 l/l in US2. All blood parameters show significant dynamics within the first week of life. The hematocrit dropped significantly in the first days of life and reached its nadir on the 3rd (US1) or 4th (US2) day of life, respectively. It started increasing again at day 6 and 7. The graphs of hemoglobin and erythrocyte count were similar to the hematocrit curve due to their strong interrelation. The erythrocytes showed the largest MCV shortly after birth on day 0 before it decreased significantly. The MCH remained stable. MCHC increased within the first 24 hours and then remained nearly stable. The dynamics of leukocytes were comparable to the hematocrit with a nonlinear decrease in midweek and an increase at day 6 and 7 of life. Platelets showed a steep, progressive course after the lowest value on day 1 of life. The significant decrease in blood parameters followed by an increase at day 6 and 7 with concomitant thrombocytosis indicated intrapartum blood loss and subsequent regeneration. The cutoff value for anemia was set at a hematocrit of weiterlesen