Hypoxic level and duration differentially affect embryonic organ system development of the chicken (Gallus gallus)

Abstract

Hypoxia inhibits avian embryonic development, as well as increases embryonic mortality. However, the key organ systems affected by hypoxia, and their critical windows for development, are poorly understood. Consequently, chicken embryos were continuously exposed to 3 levels of oxygen (21, 15, or 13% O(2)) throughout d 0 to 10, d 11 to 18, or d 0 to 18 of incubation, followed by morphometric and blood physiological measurements. Hypoxia occurring early during incubation (d 0 to 10) had larger effects on embryonic mortality and organ growth than hypoxia occurring at later stages (d 10 to 18). Growth of the heart and chorioallantoic membrane was stimulated by chronic hypoxia, whereas the lung, brain, eye, liver, stomach, beak, and toes showed no disruption. Sustained hypoxia from the beginning of incubation decreased blood hemoglobin, hematocrit, and red blood cell concentration of embryos at d 10, but the values among hypoxic and normoxic groups were not significantly different at d 18. Blood partial pressure of O(2) and partial pressure of CO(2) were dependent upon incubation O(2) level at a given day of development. These results indicated that either modest hypoxia (15% O(2)) throughout development, or hypoxia at any level during the late stages (d 11 to 18), increased the heart and chorioallantoic membrane weight, which partly compensated for the detrimental effects of hypoxia on embryonic development. We conclude that the first half of embryonic development contained the critical windows for the detrimental effects of hypoxia, and the second half contained the critical windows for the compensatory response of hypoxia in key organs.

Poultry Egg Incubation: Integrating and Optimizing Production Efficiency

“…Hypoxia during incubation has different effects on poultry embryonic and fetal development, depending on the period of embryo development, and on the duration and level of hypoxia Ferner & Mortola, 2009;Zhang & Burggren, 2012). Interestingly, Bahadoran et al (2010) found that early hypoxia (incubation at 1800m above sea level until embryonic day 10), followed by normoxia (incubation at sea level) reduces the duration of incubation, reduces the incidence of ascites, and improves the feed conversion ratio and body weight of 42-d-old broilers reared in normoxia.…”

Cardio-respiratory development in bird embryos: new insights from a venerable animal model

“…These approaches are often combined with exposure of the developing embryo to hypoxia or hypercapnia as stressors on the cardiovascular, respiratory, and acidbase balance systems to tease apart elements of cardiorespiratory physiological control (Adair et al, 1987;Strick et al, 1991;Burton and Palmer, 1992;Rouwet et al, 2002;Crossley et al, 2003a;Villamor et al, 2004;Fisher and Burggren, 2007;Copeland and Dzialowski, 2009;Lindgren and Altimiras, 2009;Acosta and Hernandez, 2012;Zhang and Burggren, 2012;Mueller et al, 2013b;Andrewartha et al, 2014;Mueller et al, 2014b;Burggren et al, 2015b;Jonker et al, 2015;Itani et al, 2016). …”

“…Both pulmonary surface area and structure are also modified to lesser or greater extents by chronic hypoxia incubation (Xu and Mortola, 1989;Azzam and Mortola, 2007;Zhang and Burggren, 2012;Lewallen and Burggren, 2015). Hypoxia also has varying degrees of effect on the morphology and performance of the heart and systemic vasculature, ranging from no effect to profound disturbance (Asson-Batres et al, 1989;Richards et al, 1991;Burton and Palmer, 1992;Altimiras and Phu, 2000;le Noble et al, 2000;Dzialowski et al, 2002;Rouwet et al, 2002;Villamor et al, 2002;Ruijtenbeek et al, 2003;Villamor et al, 2004;Chan and Burggren, 2005;Zhang and Burggren, 2012).…”

“…Hypoxia also has varying degrees of effect on the morphology and performance of the heart and systemic vasculature, ranging from no effect to profound disturbance (Asson-Batres et al, 1989;Richards et al, 1991;Burton and Palmer, 1992;Altimiras and Phu, 2000;le Noble et al, 2000;Dzialowski et al, 2002;Rouwet et al, 2002;Villamor et al, 2002;Ruijtenbeek et al, 2003;Villamor et al, 2004;Chan and Burggren, 2005;Zhang and Burggren, 2012). Corresponding with these cardiorespiratory phenotypic modifications are changes in overall metabolic rate, typically measured as oxygen consumption.…”

“…Yet again there are conflicts in the literature regarding the magnitude and even presence of the effects (Chan and Burggren, 2005;Azzam and Mortola, 2007;Zhang and Burggren, 2012). What might be the source of this variation in the morphological and physiological responses, and even the apparent timing of the critical windows, of avian embryos in response to hypoxic incubation?…”