Heart and breathing rate variability in the avian perinatal period: The chicken embryo as a model

Abstract

We used the chicken embryo at the internal pipping phase (just after the onset of pulmonary ventilation) as a model to quantify the changes in heart rate (fH), breathing frequency (fB) and their variabilities (heart rate variability and breathing rate variability) during air breathing (21% O 2) and successive 20-min periods of 15%, 10% and 5% O 2 and posthypoxic recovery. For each condition, and for both fH and fB, variability was quantified by time-domain analysis with five standard criteria; these produced qualitatively similar results, which were combined into a single variability index. In normoxia, breathing rate variability was about five times higher than heart rate variability. With 10% O 2 , the embryo's oxygen consumption ( V O 2) and breathing rate variability decreased while heart rate variability increased. In normoxia, respiratory sinus arrhythmia was recognisable in a minority of embryos; its average value was low (~2%) and decreased further with hypoxia. With very severe hypoxia (5% O 2), in some cases, breathing stopped; when it did not, breathing rate variability was high. Within the 20-min post-hypoxia, all embryos recovered, and almost all parameters (fH, heart rate variability, fB, respiratory sinus arrhythmia and  V O 2) were at the pre-hypoxic values; only breathing rate variability remained low. The possibility of simultaneous measurements of fB and fH makes the avian embryo, close to hatching, a suitable model for the investigations of heart rate variability and breathing rate variability in response to hypoxia during the transition from prenatal to postnatal life.

Effects of hypoxic conditions during the plateau period on pre- and posthatch broiler performance

“…The effect of hypoxia exposure during the plateau period of embryonic development on the cardiovascular system was significant and rapid, primarily affecting embryo HR; 6 h into hypoxia, a significant increase in HR was observed compared to controls. Elevation in HR in response to lower oxygen availability has already been documented by Tomi et al . (2019) .…”

“…Hypoxia during broiler embryo incubation has been found to trigger adaptation of the embryonic cardiovascular system to the altered environment, with elevations in blood parameters, such as hematocrit, hemoglobin ( Haron et al . 2017 ) and HR ( Tomi et al, 2019 ). The actual effects of hypoxia on embryo development depend on the critical period of exposure, hypoxia level, and duration of hypoxic exposure.…”

Post-Hatch Performance of Broilers Following Hypoxic Exposure During Incubation Under Suboptimal Environmental Temperature

“…Hypoxia during broiler embryo incubation has been found to trigger adaptation of the embryonic cardiovascular system to the altered environment, with elevations in blood parameters, such as hematocrit, hemoglobin (Haron et al, 2017), and heart rate (Tomi et al, 2019). The actual effects of hypoxia on embryo development depend on the critical period of exposure, hypoxia level, and duration of hypoxic exposure.…”

Functional assessment of avian embryo quality during incubation

“…В работах [16,17] показан контроль ЧСС как метод биологического контроля инкубации, а также как метод, позволяющий корректировать режим инкубации, основанный на частоте сердечных сокращений эмбриона. Было обнаружено, что частота сердечных сокращений эмбрионов снижается по мере того, как они развиваются.…”