Chapter 7. Conclusions

The development of shivering thermogenesis is the determinant for the beginning of endothermy in juvenile birds. The heat productive capacity of shivering develops gradually. Depending on the species, incipient shivering may have only a small capacity in sustaining body temperature in cold.

The occurrence of shivering has to be ruled out with careful and extensive measurements of the EMG before the existence of avian NST can be proved. It seems obvious that the occurrence of NST is not a general phenomenon in juvenile birds. Until further evidence can be provided, the existence of NST in young birds remains doubtful. Consequently, shivering thermogenesis is probably the only mode of regulatory heat production in juvenile chicks.

At least in some juvenile birds, postprandial heat production can be used successfully to replace shivering thermogenesis at least partially in cold, as was shown in the present study with Japanese quail chicks.

Exercise, although possessing heat production potential, is a poor source of compensatory heat production for shivering in young birds since it results in excessive heat loss due to weak insulation.

Interactions between shivering thermogenesis and other forms of thermogenesis are summarised in Fig. 5. Shivering is a flexible mode of thermogenesis and its magnitude can be adjusted according to the magnitude of obligatory thermogenesis. The adjustment works towards energy saving by avoidance of the summation of different modes of heat production. The prerequisite for successful adjustment of shivering is adequate insulation, whose role in preventing excessive heat loss is pronounced during exercise. Thus the energetics of posthatching thermoregulation includes the potential for optimization of energy use in order to avoid dissipation of waste energy as heat.