The sustained maximum rate of energy intake (SusEI) is an important variable that imposes an upper constraint on animal and human performance. Consequently, there has been intense interest in the factors that may limit it. Early hypotheses that SusEI is limited by the capacity of the alimentary tract or the activity of tissues where energy is utilised have been shown to be inadequate. A popular model for the study of SusEI has been peak lactation. We have recently suggested that the maximum SusEI at peak lactation is limited by the capacity to dissipate heat generated as a by-product of processing food and producing milk. In the current study, we performed an experimental test of this hypothesis by shaving mice during lactation to reduce their external insulation, thereby elevating their heat dissipation capacity. The heat dissipation limit theory suggests that shaved mice should have elevated performance, while alternative theories predict either no effect or reduced performance. Consistent with limits imposed by heat dissipation capacity, female mice that had been shaved ate more food, generated more milk and raised heavier offspring than unshaved individuals. These data show that ambient temperature may have direct effects on lactation, coupling mammalian reproduction much more closely to climate change than indirect effects on food supply alone. More generally, we see many situations where heat dissipation may be a previously unrecognised factor constraining the evolution of endothermic animals — for example the latitudinal and altitudinal trends in clutch and litter sizes and the migration patterns of birds.
|Number of pages||1|
|Journal||Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology|
|Publication status||Published - Jun 2009|