Abstract. Title of the paper: Effects of development quality on heart rate, activity and resting times and their diurnal rhythmicity and on growth of group housed feeder-fed dairy calves
To characterize the rhythmicity of physiological variables in dairy calves of different developmental quality and fitness (groups by hemoglobin content of blood) at early gowth (71 German Holstein Friesian, 6 German Red Pied, 36 male and 41 female) long term heart rate recordings were taken at 5, 15, 40 and 60 days of age using Polar Sport Tester, from which the number and duration of activity (ZDA) and resting times (ZDR) and the total daily activity (GZA) and resting time (GZR) could be established. For these periods characteristic heart rate values were calculated (HFA and HFR) and they were analysed for daytime periods of three hours duration at different life ages. Mean HFA and HFR were significantly different between calves of group HbG1, HbG2 and HbG3 at 5 days and 15 days of age and ZDA was significantly different at 5 and 60 days of age. HF and the increase of HF (HFA-HFR) were significantly smaller at 15 days then at 5 days of age. Mean ZDA and GZA and ZDR were greater and the GZR was smaller at 40 and 60 days then at 5 and 15 days of age. Changes of the variables by 40 and 60 days of life took place with different degrees in calves of the three groups. Deviation of HFA and HFR from the mean of the individual daytime heart rate recording showed a rhythmicity that has been affected by feed access of the calves at the feed supply station. Means of ZDA and ZDR were significantly different between daytime periods of three hours duration at the age points. Results show effects of development quality on physiological variables of calves and on the rhythmicity of the variables and what changes occur with advanced development and adaptation of the animals.