The body surface temperature of a Suffolk sheep placed outside under summer heat was measured using infrared radiation thermometer. The sheep was sheared only left side of the body. The surface temperature at the top of the head showed high temperature by exposing to the direct rays of the sun, indicating 62.5°C on 14 : 00 of August 1^st (highest temperature ; 31.8°C). Simultaneously, the temperature at the top of the topline wool (wool length ; about 10 cm) indicated 44.5°C, while the temperature at the bottom of the topline wool was nearly body temperature.
The result indicates that the preparation of sunshade like shelter tree will be very important on grazing under summer heat because the surface temperature at the top of the head of Suffolk sheep covered with black short hair will become high temperature by exposing to the direct rays of the sun, and that wool has excellent insulating effect for summer heat.

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Experiments were performed to elucidate the effects of shearing on the thermoregulatory function of sheep with a special interest in how they were modified by animal factors such as age. Twenty-one Corriedale sheep, 13 males (1 to 13 years old (Y)) and 9 females (2 to 12 Y), were used. From late April to mid May, measurements were conducted 2 or 3 days before and 1 day after shearing. After feeding, body weight and fleece depth were measured from 10 : 30. Physiological parameters were measured from 13 : 00 to 15 : 00 in a shed which prevented the outside radiation and air movement. Averages of black globe temperature, air temperature, relative humidity, and air velocity during the physiological measurement before and after shearing were 21.8 and 20.4°C, 20.9 and 19.5°C, 49 and 59%, and 0.1 and 0.0 m/sec, respectively. Fleece depth at the trunk before shearing was over 5cm in most animals, but some animals over 10 Y showed lower values. The depth after shearing was ca. 1 cm. Before shearing, rectal temperatures (RecT) in animals under 4 Y were inclined higher and more dispersed than those in animals of 4 Y and over. Shearing decreased RecT in many animals by ca. 0.2°C. Three animals under 4 Y and 2 animals over 11 Y showed larger decreases, i.e. 0.4 to 0.6°C and 0.5 to 0.9°C, respectively. After shearing, compared with the others, one of 2 Y showed a high RecT, and one of 13 Y showed a low one. Respiration rates (ResR) in many animals before shearing were over 60 and even 180 cycles/min at most. Two animals under 3 Y and 2 animals over 11 Y showed lower ResR, i.e. 30 to 50 and14 to 15 cycles/min, respectively. Shearing decreased ResR in all animals. After shearing, ResR of the 2 animals over 11 Y (ca. 10 cycles/min) were lower than those of the others (20 to 60 cycles/min). Under a resting condition, ResR of ca. 20 cycles/min is regarded as the normal value for the sheep kept in a thermal neutral environment. Judging by the ResR, many animals were considered under heat stressed conditions before shearing, but relieved of the stress by shearing. Meanwhile, some animals over 11 Y showed symptoms of cold stress after shearing, that were considered to be related to the lowered thermoregulatory function due to aging. Large dispersion of RecT and ResR in animals under 4 Y suggested that their thermoregulatory function was on a developing stage and not matured yet.

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