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 non-pregnant, non-lactating (dry) period. Heart rate rose around the morning and afternoon feedings, whereas blood pressure did not show any diurnal rhythm. Comparison between reproductive periods revealed that heart rate was higher during the fifth month of pregnancy than during lactation and the dry period, whereas for blood pressure no such differences between periods were found. Withholding three meals from lactating goats resulted in a continuous slowdown of the heart rate, whereas blood pressure fluctuated. Re-feeding temporarily increased the heart rate but had no effect on blood pressure which continued to fluctuate. After another 2 days, blood pressure (but not 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 length of time long enough to include all reproductive periods. Our results emphasize that when planning experiments it is important that the exact stage in each reproductive period, the act of feeding and the amount of food given be taken into account.