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Cardiac rhythms in developing chicks

K Moriya1, J Höchel, J T Pearson

  • 1Department of Electrical and Electronic Engineering, Muroran Institute of Technology, Japan.

Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
|February 22, 2000
PubMed

Insights

Newly hatched chicks exhibit significant heart rate (HR) variability, with distinct diurnal rhythms and three fluctuation types identified. This study details chick heart rate development and circadian patterns.

Area of Science:

  • Cardiovascular Physiology
  • Developmental Biology
  • Chronobiology

Background:

  • Investigating heart rate (HR) fluctuations in chicks is crucial for understanding avian cardiovascular development.
  • Previous studies focused on embryonic HR, necessitating continuity into post-hatch development.
  • Ascertaining diurnal rhythms of HR is key to understanding physiological regulation in young birds.

Purpose of the Study:

  • To characterize instantaneous heart rate (IHR) fluctuations in chicks from day of hatch to day 6.
  • To investigate the development of HR variability and irregularities post-hatching.
  • To ascertain circadian rhythms of HR under controlled environmental conditions.

Main Methods:

  • Non-invasive electrocardiogram measurements of IHR in chicks from day 1 to day 6.
  • Experiment I: 1-hour IHR recordings twice daily (daytime and nighttime) to assess variability.
  • Experiment II: Continuous HR measurements under natural photoperiod, thermoneutrality, and ad libitum feeding to determine circadian rhythms.

Main Results:

  • Chick IHR was significantly more arrhythmic than embryonic HR, with spontaneous accelerations dominating.
  • Three types of HR fluctuations were identified: respiratory arrhythmia (Type I), low-frequency oscillations (Type II), and non-cyclic irregularities (Type III).
  • Daytime HR (250-500 bpm) was highly variable, decreasing at night (200-350 bpm), with persistent fluctuations throughout the diurnal cycle.

Conclusions:

  • Post-hatching chick HR exhibits complex variability and distinct diurnal patterns, differing significantly from embryonic HR.
  • Respiratory arrhythmia and spontaneous accelerations are major components of chick HR fluctuations.
  • Circadian rhythms influence chick HR, with notable differences between daytime and nighttime rates and variability.

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