DOES HEAT INCREMENT REPLACE NONSHIVERING THERMOGENESIS OF BROWN ADIPOSE TISSUE IN ARCTIC UNGULATES?
Robert G. White Large Animal Research Station, Institute of Arctic Biology, University of Alaska Fairbanks, AK 99775-7000, USA. If appetite is stimulated by cold exposure, particularly within the thermoneutral zone (TNZ), then heat increment of feeding (HIF) can lead to an effective lowering of the lower critical temperature (LCT). This mechanism would be adaptive if the response is sufficient to eliminate the need for shivering thermogenesis at low ambient temperatures. Evidence from studies with reindeer shows that voluntary food intake (appetite) is stimulated by low ambient temperature in winter, and the effect takes place within the TNZ. Theoretical estimates of HIF should cause a left shift in the LCT which expands the TNZ to cover most typical winter temperatures in interior Alaska. Thus, the number of acute thermogenic responses required to meet low ambient temperature would be few. Depending on whole body insulation, implications of not being able to meet cold stimulated appet
