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- Title
Regional differences in sweat rate response of steers to short-term heat stress.
- Authors
Spiers, D. E.; Wax, L. E.; Scharf, B.; Aiken, G. E.
- Abstract
A preliminary study was performed to determine the sweat rate response to short-term heat stress using a new portable detector. Six angus steers (319.5 avg bw) were placed in two chambers maintained at 16.5 - 18.8C air temperature (Ta) within the Brody Environmental Center at the University of Missouri. Cold chamber Ta was lowered to 8.1C and Ta within the hot chamber was increased to 32.7C over a 24h period. Measurements at selected time periods included air and rectal temperatures, along with respiration rate, as indicators of thermal strain. Skin temperature was measured at shoulder and rump locations with determination of sweat rate using a Vapometer (Delfin Technologies Ltd, Finland). Rectal temperature did not change in cold or hot locations due to a known lag in this response, and to effectiveness of thermoeffector mechanisms. Respiration rate nearly doubled in the heat (P < 0.05) to maintain this core temperature. Best fit for this relationship was a fourth-order polynomial relationship (R2 =0.87; P<0.0001). This increase occurred at a Ta above 24C. Skin temperatures at the two locations were highly correlated with each other and with Ta. In contrast, sweat rate was different at rump and shoulder sites, and affected by Ta. Sweat rate of the rump exhibited only a small increase with Ta, and showed no signs of a sharp increase. However, sweat rate at the shoulder increased more than 4-fold at Ta and shoulder temperatures above 27 and 36C, respectively. Increased sweat rate in this region is supported by an earlier report of a higher density of sweat glands in the shoulder compared to rump regions. Sweat rate was correlated with several thermal measurements to determine the most likely predictor and stimulus for this response. Fourth-order polynomial expressions for rectal, shoulder and air temperatures produced R2 values of 0.37, 0.72, and 0.97, respectively. This suggests that thermal inputs, other than rectal or shoulder temperatures, drive the sweat response in the shoulder.
- Publication
Journal of Animal Science, 2006, Vol 84, p303
- ISSN
0021-8812
- Publication type
Academic Journal