Co-Authors:
Eyal, E., Division of Animal Husbandry, National and University Institute of Agriculture, Rehovot, Israel
Abstract:
1. A comparison was made between the skin temperature, humidity and temperature within and on the surface of the fleece of unshorn and shorn sheep. This study was conducted during various seasons of the year, at different environmental temperatures, while sheep were maintained in the shade or subjected to direct sunlight. 2. Accompanying the rise of ambient temperature (in the shade) from 10 to 43ͦ C. there was an increase in skin temperature from 34 to 40ͦ C. and from 28 to 40ͦ C. of the unshorn and shorn sheep, respectively. 3. The relationship between the rise in skin temperature and that of ambient temperature was not linear, but showed a stepwise pattern in which the ‘breaks’ occurred at similar environmental temperatures for both groups, although skin temperatures of shorn sheep were lower than the unshorn. 4. The diurnal change in skin temperature of the shorn sheep was similar to that of the ambient temperature. The decrease in skin temperature of unshorn sheep sometimes lagged behind the fall in environmental temperature. The seasonal variations between summer and winter were more significant in shorn than in unshorn sheep. 5. Fleece surface temperatures measured at the same ambient temperatures ranged between 13 and 42ͦ C. and 16.539.5ͦ C. in the unshorn and shorn sheep, respectively. In the break points of the rise in skin temperature, there occurred a drop in temperature gradients between the skin and fleece surface. This probably indicates a rise in thermal conductivity of the fleece at these points. 6. The temperature gradient per unit of fleece thickness is inversely related to the depth of fleece and is greater the nearer to the skin. 7. With exposure to the sun, skin temperatures of both groups greatly increased and occasionally reached 47ͦ C. Under these conditions the differences between shorn and unshorn groups were not consistent. 8. Fleece temperatures of unshorn sheep increased greatly upon exposure to the sun. The maximal temperatures were recorded midway between the fleece surface and skin. These temperatures generally reached 55ͦ C. and sometimes even exceeded 60ͦ C. 9. At ambient temperatures of 3035ͦ C. the vapour pressure close to the skin of unshorn sheep ranged between 3540 mm. Hg. With shorn sheep, however, the vapour pressure close to the skin was similar to that of the environment. In Yotvata there was a rise in vapour pressure close to the skin when the ambient temperature increased to 4043ͦ C. This rise in humidity was paralleled by a rise of vapour pressure throughout the wool. It was not linear but rather showed a ‘step-wise’ pattern. 10. The vapour pressure in fleece and near the skin of sheep subjected to direct sunlight increased considerably (up to 80 mm. Hg). This rise showed a wave-like curve with various degrees of persistency. Appearance of fluid on the skin of Awassi sheep was observed on several occasions. © 1963, Cambridge University Press. All rights reserved.
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מונוכרום
הדגשת קישורים
חסימת אנימציה
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