Shorn and unshorn Awassi sheep III. Respiration rate

Abstract

1. Respiration rate of shorn and unshorn sheep was compared; animals were maintained in the shade and in direct sunlight during various seasons of the year, and at different hours of the day. The average respiration rate, for all seasons when sheep were maintained in the shade, was 55 and 32 respirations per minute, for the unshorn and shorn sheep, respectively.The diurnal trend of the respiration rate of shorn sheep resembled that of the ambient temperature. There was a delay in the lowering of respiration rate of the unshorn sheep during the evening hours.2. The critical temperature for the increase in respiration of animals maintained in the shade was 22° C. and 26–30° C. for the unshorn and shorn sheep, respectively.When the animals were exposed to the direct sunlight the critical ambient temperature for the increase in respiration rate was 15–18° C. and 18–22° C. for the unshorn and shorn sheep, respectively. The respiration rate of the shorn sheep exceeded that of the unshorn but decreased very steeply when the animals returned to the shade.3. The effect of humidity was noted particularly with ambient temperatures exceeding 27° C. The respiration rate of the unshorn sheep increased and that of the shorn decreased with the rise in the relative humidity. In the sun there was a rise in the respiration rate of both groups with increase in humidity. The rise was steeper in the shorn animals.4. The effect of the wind in reducing respiration rate was particularly noted on shorn sheep and at elevated ambient temperatures.5. With equal rectal temperature, the respiration rate of shorn sheep was lower than that of the unshorn ones. Assumed critical rectal temperature for the rise in respiration rate was lower in the unshorn sheep.6. The differences between the respiration responses of the unshorn and shorn sheep stemmed from the variation in their thermal balance. The latter resulted from the differences in the insulating characteristics of body surface and the differences between the macroclimate and the microclimate existing in the fleece.