Development of Heart Rate Circadian Rhythm in Chickens

Abstract

In chick embryos, various instantaneous heart rate (IHR) fluctuations (e.g. HR variability, HR irregularities) have been found and developmental patterns of mean heart rate (MHR) have been elucidated. IHR changes have also measured in newly hatched and young chickens in order to investigate the developmental patterns of MHR and any potential diurnal HR rhythmicity such as a circadian rhythm. The present report reviews measurements of embryonic and hatchling HR fluctuations and examine development of HR circadian rhythms during the late stages of incubation and after hatching. Embryonic HR was continuously measured during the last half period of incubation. After hatching, continuous measurements of HR were made for two weeks at the longest in eight chickens ranging in age from 0 to 47 days. During the embryonic development, circadian rhythm of HR was found to be absent until hatching. After hatching, distinct circadian rhythm of HR appeared with increasing daily MHR from day 0 to day 7. During the second week of post-hatch life, the daily scope of MHR (diurnal maximum-nocturnal minimum) reached a maximum level ranging from 200 to 300 bpm with constant baseline of nocturnal MHR. In young chicks, the nocturnal HR baseline was the same as that during the fortnight of posthatch life and daily scope of MHR decreased to 100^150 bpm.

Comparative Study of Growth and HSP70 Gene Transcription in Japanese Quails fed Different Levels of Black Soldier Fly, Hermetia illucens

“…Hence, males had a significantly higher body temperature than females. Nonetheless, females showed higher oxygen consumption than for males (Ward et al, 2002;Moriya et al, 2004;Dart et al, 2002;Green et al, 2001;Chaid, 2020). Unfortunately, the oxygen consumption, body temperature and heart rate were not measured in this study.…”

Heart Rate Responses to Acoustic Stimuli in Prenatal Chick Embryos

“…Electrocardiogram readings (ECG) were taken every 24 h starting from Day-16 of incubation, which marks the beginning of autonomic nervous system (i.e., sympathetic and parasympathetic nervous systems) development in embryos, before hatching on Day-20. IHR was determined offline based on adjacent R waves on the ECG (6)(7)(8) .…”

“…In chick embryos, low frequency (LF) and high frequency (HF) components are 0.04-0.15 Hz and 0.1-1.0 Hz, respectively (8,10,12) . HF component is the index of parasympathetic nervous system activity and the LF/HF ratio is the index of sympathetic nervous system activity.…”

“…Although the respiration of chick embryos changes from gas exchange through the egg shell to breathing with lungs during hatching, the measurement of cardiovascular parameters is possible even in periods of drastic respirational change, i.e., the prenatal period. Therefore, physiological parameters in chick embryos have been investigated to be a suitable and independent embryonic measurement model, particularly for cardiovascular systems, during the prenatal and hatching periods (e.g., [4][5][6][7][8] .…”

Measurements of Body Movement in Chick Embryos During Early Stages

“…Among these, embryonic physiological parameters that are not influenced by maternal health conditions can be measured, and assessments of responses to changes in temperature, humidity, and oxygen concentrations can be made, as shown previously (1)(2)(3) . Fertile chicken eggs can also be easily obtained from chicken farmers and physiological parameters in chick embryos have been considered suitable and independent indicators of embryonic development at all incubation periods, particularly in studies of cardiovascular system development (4)(5)(6)(7)(8)(9) . Although measurements of bio-signals during the early stages of pregnancy in mammals are extremely difficult, those of early stages (until day-7) in chick embryos can be achieved with relative ease.…”