Heart rate and diurnal rhythmicity in suckler calves from a suckler herd at different ages

Long term heart I are recordings of suckler calves (German Red Pied, German Black Pied) were made at 10, 20, 30, 45 and 65 days of age using a Polar S port Tester: The body weights were mueasured before the heart I-ate recordi ngs from which the number and duration of activity periods could be establi shed. Characteristic heart rate values for these periods were calculated (H FA and HFR) and were analysed for day time period of 3 hours duration. HF s howed substantial variation between animals and a high individual specifici ty. Mean HFA and HFR were significantly different at all ages and between a ge groups. HFA and HFR of the day time periods were not significantly diffe rent. There was cyclical variation of HF during the course of the day, but no circardian rhythm was observed. Significant differences in the mean devi ations of HFR for the day time periods were found in some cases. Sympatheti c activations during feeding, motor activity and with increasing age were e stablished as the main effects on HF of the calves.