Telemetric registration of heart rate and blood pressure in the same unrestrained goats during pregnancy, lactation and the non-pregnant, non-lactating period

The purpose of this study was to investigate how changes in heart rate and arterial blood pressure relate to the time of day, reproductive period and feeding routines in dairy goats (Capra hircus). Registrations were made by radiotelemetry in the same four goats during pregnancy, lactation and the n on-pregnant, non-lactating (dry) period. Heart rate rose around the morning and afternoon feedings, whereas blood pressure did not show any diurnal rh ythm. Comparison between reproductive periods revealed that heart rate was higher during the fifth month of pregnancy than during lactation and the dr y period, whereas for blood pressure no such differences between periods we re found. Withholding three meals from lactating goats resulted in a contin uous slowdown of the heart rate, whereas blood pressure fluctuated. Re-feed ing temporarily increased the heart rate but had no effect on blood pressur e which continued to fluctuate. After another 2 days, blood pressure (but n ot heart rate) had stabilized. Food-restriction, aimed at terminating milk production resulted in a consistently depressed heart rate and reduced the mean and systolic blood pressures at night. The results show that with this implantable telemetry device it is possible to measure both heart rate and blood pressure day and night in the same unrestrained animals over a lengt h of time long enough to include all reproductive periods. Our results emph asize that when planning experiments it is important that the exact stage i n each reproductive period, the act of feeding and the amount of food given be taken into account.