Embryonic Thermal Manipulation Affects Ventilation, Metabolism, Thermal Control and Central Dopamine in Newly Hatched and Juvenile Chicks.

Aline C G Rocha,Luciane H Gargaglioni,Caroline Cristina-Silva,Camila L Taxini,Raphael E Szawka,Kaoma Stephani Da Costa Silva,Kênia C Bícego,Virgínia T M Lima,Marcos Macari

doi:10.3389/fphys.2021.699142

Abstract

The first third of incubation is critical for embryonic development, and environmental changes during this phase can affect the physiology and survival of the embryos. We evaluated the effects of low (LT), control (CT), and high (HT) temperatures during the first 5 days of incubation on ventilation (E), body temperature (Tb), oxygen consumption (O2), respiratory equivalent (E/O2), and brain monoamines on 3-days-old (3d) and 14-days-old (14d) male and female chickens. The body mass of LT animals of both ages and sexes was higher compared to HT and CT animals (except for 3d males). The heart mass of 14d HT animals was higher than that of CT animals. Thermal manipulation did not affect E, O2 or E/O2 of 3d animals in normoxia, except for 3d LT males E, which was lower than CT. Regarding 14d animals, the HT females showed a decrease in E and O2 compared to CT and LT groups, while the HT males displayed a lower O2 compared to CT males, but no changes in E/O2. Both sexes of 14d HT chickens presented a greater Tb compared to CT animals. Thermal manipulations increased the dopamine turnover in the brainstem of 3d females. No differences were observed in ventilatory and metabolic parameters in the 3d animals of either sexes, and 14d males under 7% CO2. The hypercapnic hyperventilation was attenuated in the 14d HT females due to changes in O2, without alterations in E. The 14d LT males showed a lower E, during hypercapnia, compared to CT, without changes in O2, resulting in an attenuation in E/O2. During hypoxia, 3d LT females showed an attenuated hyperventilation, modulated by a higher O2. In 14d LT and HT females, the increase in E was greater and the hypometabolic response was attenuated, compared to CT females, which resulted in no change in the E/O2. In conclusion, thermal manipulations affect hypercapnia-induced hyperventilation more so than hypoxic challenge, and at both ages, females are more affected by thermal manipulation than males.

Highlights

Incubation is a period of high plasticity, when the environment experienced by the embryo can significantly alter the physiological systems of post-hatch life (Walstra et al, 2010)
In 14d low temperature (LT) males (P < 0.0001) and females (P = 0.005), Body mass (BM) was higher compared to the CT and high temperature (HT) groups (Table 1)
We demonstrated that incubation at a high temperature during a “critical window” of organogenesis (Burggren, 1998) decreases V E, decreases V O2, and increases Tb in 14d chickens under room air conditions, practically regardless of sex

Summary

Introduction

Incubation is a period of high plasticity, when the environment experienced by the embryo can significantly alter the physiological systems of post-hatch life (Walstra et al, 2010). Changes in embryonic temperature can accelerate or slow down embryo growth and/or metabolism (Tazawa and Rahn, 1987; Tazawa et al, 1989; Christensen et al, 1999; Lourens et al, 2005; Mortola and Toro-Velasquez, 2013), altering the development of vital organs, such as the heart and lungs (Molenaar et al, 2011) The severity of these effects depends on the intensity and duration of the stimulus and the phase of incubation (Webb, 1987; French, 1997; Dzialowski et al, 2002; Mortola and Labbè, 2005). Thermal alterations during incubation can affect brain regions involved in thermoregulation, such as the proportion between warm- and cold-sensitive neurons in the hypothalamus of hatchling and juvenile ducks (Tzschentke and Basta, 2002)

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