Responses of unshorn and shorn sheep to thermal stress

1. The effect of close shearing upon the respiratory frequency of ewes at ambient temperature of 20 degrees C and 55% relative humidity has been described.2. Removal of an adequate area of fleece (3000 cm(2) or more) on the thoraco-lumbar region resulted in a depression of respiratory responses and this was attributed to the exposure of cold receptors located beneath the fleece.3. The continued depression of respiratory frequency of partially shorn sheep (3000 cm(2)) during rising ambient temperature appears to be due to persistence of cold receptor drive originating from the shorn area.4. The absence of any rise in carotid blood temperature before the onset of polypnoea in unshorn sheep, during rising ambient temperature, suggests that the onset of panting in sheep can occur almost immediately upon a rise in ambient temperature even in the absence of any rise in the temperature of the blood supplying the brain.