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Low-frequency oscillation of instantaneous heart rate in newly hatched chicks
Hiroshi Tazawa1, Kenji Moriya, Akihiko Tamura
1Department of Electrical and Electronic Engineering, Muroran Institute of Technology, 050-8585, Muroran, Japan. tazawa@elec.muroran-it.ac.jp
Insights
Heart rate oscillations in newly hatched chicks are linked to thermoregulation. Environmental temperature significantly influences these heart rate variations (HRV), with lower temperatures increasing oscillations.
Area of Science:
- Physiology
- Animal Science
- Thermoregulation
Background:
- Heart rate fluctuations in chickens emerge during late incubation and intensify post-hatching.
- These fluctuations are classified into high-frequency (Type I HRV), low-frequency (Type II HRV), and irregular accelerations (Type III HRI).
Purpose of the Study:
- To investigate the origin of Type II heart rate variability (HRV) in newly hatched chicks.
- To determine the relationship between Type II HRV and thermoregulation in response to environmental temperature changes.
Main Methods:
- Newly hatched chicks were exposed to varying ambient temperatures.
- Heart rate (HR) and its fluctuations were monitored under different thermal conditions.
Main Results:
- Type II HRV was induced or amplified by exposure to lower ambient temperatures.
- Elevated environmental temperatures abolished Type II HRV.
- Greater decreases in temperature led to more pronounced increases in baseline HR.
Conclusions:
- Low-frequency heart rate oscillations (Type II HRV) in newly hatched chicks are strongly associated with thermoregulation.
- Environmental temperature is a critical factor modulating Type II HRV, suggesting a role in maintaining thermal homeostasis.
Abstract:
Instantaneous heart rate (IHR) of chickens began to fluctuate on days 13-14 of incubation and heart rate (HR) fluctuations became augmented towards hatching and increased further after hatching. IHR fluctuations of newly hatched chicks have been categorized into three types: type I HR variability (HRV), which is high-frequency oscillation; type II HRV, which is low-frequency oscillation; and type III HR irregularities (HRI), which are irregular HR accelerations. The present experiment was carried out to investigate the origin of type II HR oscillations. Following previous evidence, we assumed that the low-frequency oscillation of HR in newly hatched chicks was related to thermoregulation and changed by environmental temperature. Eventually, type II HRV was produced or augmented by exposure of hatchlings to lowered ambient temperature and was abolished by exposure to elevated environmental temperature. The hatchlings that were exposed to large temperature decreases tended to increase their HR more than those exposed to small temperature decreases, and vice versa. The HR oscillation accompanied by an elevation of HR baseline in response to cooling may be a phenomenon related to thermoregulation in chick hatchlings.