title: Low-frequency oscillation of instantaneous heart rate in newly hatched chicks.
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.
authors.affiliation: Department of Electrical and Electronic Engineering, Muroran Institute of Technology, 050-8585, Muroran, Japan. tazawa@elec.muroran-it.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tazawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Moriya
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tamura
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Akiyama
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002645:Chickens / Q000502:physiology*; D006339:Heart Rate