Thermoregulatory responses to egg cooling in incubating bantam hens
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Summary
O2 consumption, electromyographic activity (EMG), heart rate (HR), cloacal temperature (Tb) and broodpatch temperature (Tsb) were measured in bantam hens incubating eggs of different temperatures (Te). For comparison, the metabolic response to low ambient temperature (Ta) was measured in non-incubating hens.
O2 consumption increased nearly linearly with decreasingTe down to 30°C. At this temperature O2 consumption was about 3.5 x the resting level. Below 30°C O2 consumption increased non-linearly, and reached 4.6 x the resting consumption at 15°C. Eggs of 10 and 0°C gave no further increase. Pectoral muscle EMG and HR also increased in response to egg cooling. The onset of egg cooling was associated with a decrease inTb andTsb. Hens exposed to lowTa showed a lower critical temperature of about 24°C.
It is concluded that heat loss from the brood-patch during incubation of cold eggs is compensated by shivering thermogenesis. AtTe below 15°C heat production is at a maximum level, corresponding to the expected O2 consumption at exposure to an ambient temperature of −65°C.
Keywords
Heart Rate Ambient Temperature Human Physiology Critical Temperature Heat LossAbbrevations
- EMG
electromyography
- Ta
ambient temperature
- Tb
cloacal temperature
- Te
egg temperature
- Tsb
brood-patch skin temperature
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