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Influence of air humidity on the partition of heat exchanges of cattle

Published online by Cambridge University Press:  27 March 2009

J. A. McLean
Affiliation:
Department of Physiology, Hannah Dairy Research Institute, Ayr
D. T. Calvert
Affiliation:
Department of Physiology, Hannah Dairy Research Institute, Ayr

Summary

The balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.

Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.

Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.

Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.

Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1972

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