Abstract. Title of the paper: Effects of a single oral iron application on growth and on hematological variables, hemoglobin derivatives and blood gas content in group housed feeder-fed dairy calves
To characterize physiological variables in dairy calves of different developmental quality and fitness (hemoglobin content of blood low HbG1, moderate HbG2 and high HbG3) at early gowth with uniform husbandry system on dairy calves (71 German Holstein Friesian, 6 German Red Pied, 36 male and 41 female) measurements were done before (5 days of age) and repeatedly at 15, 40 and 60 days of age when calves were kept in groups with automatic feeding. Mean birth weight was not different between groups. Growth performance of calves of HbG1 was smaller then that of calves in HbG2 and HbG3. Correlations of birth weight and body weight at the following testing points with the growth criteria were of different degree within the groups. Hematological variables of the calves within the three groups changed with growth in different ways. Significant mean value differences between groups could be found for Hb, O₂CAP, O₂CONT, MetHb up to 40 days, for Hk, HHb, and for O₂SAT up to 60 days, for MCHC up to 15 days, and for the lactate concentration at 40 days and 60 days of age. The prophylactic single oral iron application of 1000 mg in calves at birth and the iron supply of 100 mg/kg by milk replacer led to plasmairon concentrations of 20 to 40 μmol/l, but the erythropoietic reactions in the calves were different. Relationships between the quality of erythropoiesis and iron access were assessed considering the changes of the physiological variables and the initial situation in calves at birth.