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1.|Measurements of metabolic heat production, body temperature (Tb), evaporative heat loss (−E) and leg-shank skin thermal circulation index were made on groups of fed and starved 1-week-old chicks exposed to constant ambient temperatures (Ta) within the range 10–40°C.
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2.|In the cold the heat requirement of starved chicks was less than that of fed chicks by an amount similar to the heat increment of food.
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3.|From the upper to the lower critical temperature the Tb of starved chicks decreased by up to 2°C compared with the relatively constant level maintained by fed chicks. Between the lower critical temperature and the temperature of peak metabolic rate a difference in Tb of 2°C was maintained between the two groups.
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4.|The onset of peripheral vasodilication occurred between Tas 25 and 28°C with fed chicks, but Ta 30–33°C by starvation.
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5.|Increased −E was initiated only when Tb exceeded about 41.3°C, when Ta exceeded 34°C in fed bird or 36°C in starved birds