Skin and core temperatures as determinants of heat production and heat loss in the goat

In 82 experiments on 10 goats body core temperature (T_core) was altered between 35° and 42°C by external heat exchangers acting on blood temperature while skin temperature (T_skin) was maintained constant, by a circulating shower bath, at different levels between 32° and 44°C. At all skin temperatures at least fourfold increases of heat production (M) and respiratory evaporative heat loss (REHL) occurred whenT_core was lowered or raised, respectively. The lower T_skin was, the higher were the thresholds ofT_core, at which M or REHL exceeded resting levels. The lower T_skin was, the higher were the slopes, at which M or REHL changed per unit ofT_core. At a given T_skin, the slopes decreased with increasing M or REHL, and were dependent on the range ofT_core. The higher the range ofT_core, the steeper changed M and REHL with changingT_core, if all other variables were held constant. The results support the concept that an exponential relationship betweenT_core and the rate of core temperature signals is the primary cause of the effects exerted by T_skin on the slopes, at which M or REHL change per unit ofT_core.