J. Anim Sci.
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J. Anim Sci. 1956. 15:141-152.
© 1956 American Society of Animal Science
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Correlations between Ambient Temperatures Varying from 60°–95° F. and Certain Physiological Responses in Young Dairy Bulls1

R. B. Casady, J. E. Legates and R. M. Myers

North Carolina State College

Abstract

In two experiments, four Holstein bulls were subjected to continuous exposure in environmental chambers to air temperatures of 60°, 70°, 80°, 85°, 90° and 95° F., at absolute humidities of 10.0 to 14.5 mm. Hg. Treatment periods at each of the above temperatures ranged from 29 to 50 days in duration.

Correlations for each treatment period, between rectal temperatures and the physiological responses of respiratory rate, rump skin temperature and scrotal skin temperature, were lower than the correlations between chamber temperature and the same responses. On the other hand, water consumption was more closely related to rectal temperature than chamber temperature.

Respiratory rates were most closely associated with rectal temperatures at air temperatures of 80°–90° F. At temperatures above 90°–95° F. respiratory rates were not closely associated with rectal temperatures and could not be used as indices of thermal stress.

The results indicate that skin temperature was not a precise reflection of changes in the animal's internal environment.

A possible age difference in response to high ambient temperatures was exhibited by a delay in responses of respiratory rate and rectal temperature to increased ambient temperature during the second experiment. There was no marked response in either variable until the ambient temperature reached 90° F. as compared to initial responses at 70°–80° F. in the first experiment.

Footnotes

1 Approved for publication as paper No. 666 in the Journal Series of the North Carolina Agr. Exp. Sta., Raleigh.






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Copyright © 1956 by the American Society of Animal Science.