Cardiovascular changes associated with dehydration and drinking in unrestrained, lactating goats

The aim of this study was to investigate if the alertness connected with se eing water increased arterial blood pressure and heart rate to the same ext ent as the act of drinking, and if ingestion of warm water caused a differe nt effect compared with ingestion of cool water on these cardiovascular var iables. Seven goats of the Swedish domestic breed (Capra hirus) were used i n a cross-over design. The animals were dehydrated for 24 h. They were allo wed to watch water being prepared for 11-16 min, after which they were give n access to warm (35 degrees C) or cool (15 degrees C) water. The gears dra nk 6.86 +/- 0.36 1 of the warm water and 4.54 +/- 0.35 1 of the cool water (P < 0.05) within the first hour. The arterial blood pressure, heart rate a nd activity of the animals were registered by an implanted telemetric devic e. Dehydration did not affect the cardiovascular variables, except before f eeding in the morning, when the heart rate accelerated Faster in dehydrated goats. Heart rare increased abruptly when dehydrated goats saw water being prepared, remained at the increased level during drinking and then slowly declined. It increased again during the afternoon feeding, to a level simil ar to that on control days, but between 18.00 and 06.00 h the heart rate wa s higher than during control nights. Blood pressure did not change when the goats saw water, but increased when they drank. On the morning following r ehydration, the rise in heart rate in response to feeding was delayed compa red with that during control and dehydration periods. it is concluded that seeing water caused arousal in the goats, resulting in an accelerated heart rate. The additional rise in blood pressure during the act of drinking app ears to be a combination of excitement and sensory inputs from the pharynge al region, causing a temporary activation of the sympathetic nervous system .