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Selective brain cooling reduces water turnover in dehydrated sheep
W Maartin Strauss1, Robyn S Hetem2, Duncan Mitchell2
1Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Department of Environmental Sciences, College of Agriculture and Environmental Sciences, University of South Africa, Johannesburg, South Africa.
Selective brain cooling in sheep helps conserve water during heat exposure and dehydration. This process lowers brain temperature, reducing water loss by up to 60% daily.
Area of Science:
- Physiology
- Animal Science
- Thermoregulation
Background:
- Arterial blood cooling in artiodactyls occurs via selective brain cooling in the cavernous sinus.
- Selective brain cooling lowers hypothalamic temperature, potentially aiding water conservation.
Purpose of the Study:
- To test if selective brain cooling contributes to water conservation in sheep under heat stress and water deprivation.
Main Methods:
- Nine Dorper sheep were exposed to heat (40°C) and water deprivation for 8 days.
- Carotid blood and brain temperatures were measured, along with plasma osmolality and body water fraction.
- Deuterium oxide (D2O) was used to assess water turnover.
Main Results:
- Dehydration increased selective brain cooling magnitude and duration in sheep.
- Greater selective brain cooling was positively correlated with osmolality and negatively correlated with water turnover.
- Sheep employing more efficient selective brain cooling lost significantly less water.
Conclusions:
- Selective brain cooling functions to conserve water in artiodactyls.
- Sheep can save substantial water (up to 2.6L/day) by utilizing selective brain cooling during heat exposure when dehydrated.
