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The Effects of Air Temperature and Relative Humidity on the Physiological well being of Swine¹

University of California^,3

Abstract

Swine of various weights were kept in a psychrometric room for periods averaging seven days with temperatures ranging from 40 to 115 degrees F. with comparatively constant relative humidity and air flow.

As the air temperature increased the body temperature and respiration rate (breaths per minute) increased and the pulse rate decreased. As the air temperature increased the rate of change in body temperature, respiratory rate and pulse rate increased.

Feed consumption decreased as the air temperature increased. Under the conditions of these experiments rate of gain was greatest and the amount of feed required to produce 100 pounds gain least at an average temperature of approximately 75 degrees F. for hogs weighing 70 to 144 pounds and approximately 60 degrees F. for hogs weighing 166 to 260 pounds. As the air temperature was increased or decreased beyond these averages, rate of gain declined and utilization of food was lowered.

At 96 degrees F. a rise in relative humidity from 30 to 94 percent produced rapid distress in hogs weighing over 200 pounds, and the respiration rate and body temperature increased rapidly.

The profound cooling effect of the evaporation of water was demonstrated. The further cooling effect of increased air motion on wet hogs has been shown as has the lack of effect of increased air motion on hogs on a dry floor when their skin temperatures are less than the temperature of the environment.

The behavior of swine under these conditions is discussed as are the autopsy findings of one animal which died at 100 degrees F.

¹ This is a cooperative project between the Division of Farm Buildings and Rural Housing, Bureau of Plant Industry, Soils, and Agricultural Engineering, U. S. Dept. of Agric., and the Divisions of Animal Husbandry and Agricultural Engineering of the University of California.

² The authors would like to take this opportunity to express their appreciation to C. F. Kelly, Agricultural Engineer, Bureau of Plant Industry, Soils and Agricultural Engineering, U. S. Dept. of Agric, for his assistance in carrying on this project and his suggestions in the preparation of this manuscript.

³ Division of Animal Husbandry, Davis, California.