Effects of dehydration and rehydration on body temperatures in the black Bedouin goat

Abstract

The temperatures of the arterial blood and the brain in black Bedouin goats were measured continuously by miniature data loggers. The animals were either euhydrated or dehydrated to 75-80% of the initial body mass by withholding water for 3-4 days during exposure to intense solar radiation. The daily blood temperature means and maxima of were significantly higher in dehydration than in euhydration, but 40 degreesC was rarely exceeded even during the hot hours of the day. Selective brain cooling occurred in euhydration, but its extent was small when blood temperature was below 39.5 degreesC. In dehydration, however, selective brain cooling was frequent and the standard response when blood temperature exceeded 39 degreesC. We believe that selective brain cooling contributes to the inhibition of evaporative heat loss, which is the primary cause of the higher blood temperature in dehydration. Rapid rehydration with cold water induced long-lasting depression of blood temperature. No evidence was found for mechanisms attenuating the subsequent decrease of brain temperature which occurred a few minutes after the uptake of cold water.

Physiological and behavioral basis for the successful adaptation of goats to severe water restriction under hot environmental conditions

“…Thus, the reduction in heart rate in the water-restricted goats suggests that they reduced their metabolism in order to conserve water and to compensate for the reduction in feed intake. The RR, even in treatment 1, was much lower than those induced under combination of dehydration and heat stress (Baker, 1989;Jessen et al, 1998), indicating that the goats in the present experiment were still far from situations that necessitate induction of heavy panting to maintain thermoregulation (Silanikove, 2000a).…”

“…Nevertheless, the increase in deep (rectal) temperature and udder skin temperature were quite modest in comparison with the responses of animals that were exposed to severe heat stress (Silanikove, 2000a), indicating that the heat stress under the present conditions did not induce significant challenge on the thermoregulation capacity of the goats. For comparison, under dehydration, the mean daily maxima of deep temperature was 0.5°C to 0.9°C higher in dehydrated goats than in hydrated ones, which was a result of a reduction in evaporative heat loss (Baker, 1989;Jessen et al, 1998). Thus, only in treatment 1, in which the restriction level was 90% of control, the prevailing heat stress induced an increase in deep body temperature that resembled a modest response under combined effects of heat stress and dehydration.…”

Enteral fluid therapy through nasogastric tube in rumen cannulated goats

“…Jessen et al (1998) offered water in different temperatures for Bedouin goats and reported that body temperature changed according to the temperature of the water, but this effect was observed only for a few seconds. The most likely explanation for the variation of rectal temperature is the nychthemeral variation (Kleiber 1975).…”

Shearing at the end of summer affects body temperature of free-living Angora goats (Capra aegagrus) more than does shearing at the end of winter

“…Also, we deprived the goats of drinking water in March, as could occur in summer seasons they might encounter, but not in winter. Water deprivation increases abdominal temperature in heat-stressed goats (Nijland and Baker, 1992;Jessen et al, 1998), but there is no evidence that short-term water deprivation compromises thermoregulation in animals not exposed to heat stress (Baker and Doris, 1982;Fuller et al, 2007).…”