Hypoxia during embryonic development increases energy metabolism in normoxic juvenile chicks

Abstract

Environmental changes during perinatal development can affect the postnatal life. In this sense, chicken embryos that experience low levels of O over a specific phase of incubation can have their tissue growth reduced and the ventilatory response to hypoxia blunted, at least until hatching. Additionally, exposure to low level of O after birth reduces the thermogenesis as well. In the present study, we tested the hypothesis that hypoxia over the third week of incubation affects the thermoregulation of juvenile chicks at an age when thermogenesis is already expected to be well-developed. To this end, we measured body temperature (Tb) and oxygen consumption (V̇0) under acute hypoxia or different ambient temperatures (Ta) of 1 and 10day-old chicks that have been exposed to 21% O2 for entire incubation (Nx) or to 15% O in the last week of incubation (Hx). We also assessed the thermal preference under normoxia or acute hypoxia of the older chicks from both incubation groups in a thermocline. Hypoxia over incubation reduced growth but did not affect the cold-induced thermogenesis in hatchlings. Regarding the juvenile Hx, present data indicate a catch up growth with higher resting V̇0, a thermal preference for warmer Tas and a possible higher thermal conductance. In conclusion, our results show that hypoxia over the third week of incubation can affect the thermoregulation at least until 10days after hatch in chickens.

Parabronchial remodeling in chicks in response to embryonic hypoxia

“…Hypoxia during incubation did not affect body mass in either group of chicks (Table 1), corroborating results from previous studies on hatchlings Lourens et al, 2007;Ferner and Mortola, 2009), but differing from others showing smaller (Hassanzadeh et al, 2004;Dzialowski et al, 2002;Amaral-Silva et al, 2017) or larger chicks (Bahadoran et al, 2010). It is known that hypoxia decreases yolk consumption (Chan and Burggren, 2005), which may be the reason for the absence of changes in body mass in our hatchlings.…”

“…Moreover, the changes observed in our hatchlings became more pronounced in 10-day-old chicks, which might be related to physiological changes induced by hypoxia during embryonic development. Increased metabolic rate, possibly related to catch-up growth, is indeed observed in 10-day-old chicks submitted to the same hypoxia treatment as that of the present study (Amaral-Silva et al, 2017). In contrast to the differences found in parabronchial structure volumes and respiratory surface area, the thickness of the tissue barrier did not differ between treatments at either age (Table 4).…”

“…In addition, this effect would last longer than the incubation phase, even under normoxic conditions after hatching. This latter idea is based on evidence of long-lasting physiological and morphological effects of hypoxia in hatchlings that returned to normoxia (Dzialowski et al, 2002;Hassanzadeh et al, 2004;Szdzuy and Mortola, 2007;Mortola, 2009;Ferner and Mortola, 2009;Amaral-Silva et al, 2017). Thus, we hypothesized that hypoxia exposure during the embryonic development of parabronchial structures affects their morphology, and that this effect endures after hatching.…”

Regulated hypothermia in response to endotoxin in birds

“…Regulated hypothermia (often referred to as anapyrexia) can be launched by birds facing other challenging conditions such as hypoxia and during daily torpor triggered by a seasonal decrease in food and/or water availability (McKechnie & Lovegrove, 2002;Butler, 2004;Bicego et al 2007;Ruf & Geiser, 2015;Amaral-Silva et al 2017;Meir et al 2019). Therefore, it is reasonable to hypothesize that regulated hypothermia occurs in birds severely challenged by pathogens.…”

Embryotoxicity and Physiological Compensation in Chicken Embryos Exposed to Crude Oil

“…Indeed, the physiological adjustments launched during the embryonic phase are possibly still effective beyond hatching. For example, hatchlings that received hypoxia in the second half of embryonic development present increased gas exchange structures in the lung and bigger decreases in metabolic rate when exposed to an acute hypoxic event (do Amaral‐Silva et al 2017, 2019).…”