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

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 (V.E), body temperature (Tb), oxygen consumption (V.O2), respiratory equivalent (V.E/V.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 V.E, V.O2 or V.E/V.O2 of 3d animals in normoxia, except for 3d LT males V.E, which was lower than CT. Regarding 14d animals, the HT females showed a decrease in V.E and V.O2 compared to CT and LT groups, while the HT males displayed a lower V.O2 compared to CT males, but no changes in V.E/V.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 V.O2, without alterations in V.E. The 14d LT males showed a lower V.E, during hypercapnia, compared to CT, without changes in V.O2, resulting in an attenuation in V.E/V.O2. During hypoxia, 3d LT females showed an attenuated hyperventilation, modulated by a higher V.O2. In 14d LT and HT females, the increase in V.E was greater and the hypometabolic response was attenuated, compared to CT females, which resulted in no change in the V.E/V.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.

Thermal Manipulation: Embryonic Development, Hatchability, and Hatching Quality of Broiler Chicks

“…Short-term (intermittent) alteration in incubation temperature during varying age of embryogenesis can boost muscle growth and development at hatch and in the first weeks post-hatch (early period (E0-E5) [22]; mid-term (E16-E18) [59]; long-term (E12-E18 and E10-E21) [60]). In the current review, the similar effect was identified with short and long-term TM (36.8°C for 24 h/d from E7 to E13 [32]; 39°C for 9-18 h/d from E10 to E18 [37,50]; 36.°C for 6 h/d from E10 to E5 [2]), which was indicated by increased embryo, hatch and 1-day-old chick weight. In addition, it is evidenced that TM has significant effect on proliferation and differentiation of satellite cells, and thus growth and development of embryonic and chick muscles [61].…”

“…Among the 24 intermittent TM studies, 20 articles reported the TM effect on hatchability, of which 65% found no significant effect, 30% being reduced, and a comparative study by Dalab and Ali [46] reported increased and decreased hatchability at different embryonic age. Meanwhile, embryo and/or hatch weight and chick quality were reported in 18 articles, of which 12 (67%) found no significant effect, three studies reported increased [2,38,50], and three reported reduced effect of TM on embryo and/or hatch weight and chick quality [42,45,46].…”

“…Among the seven comparative studies, low-temperature TM resulted in increased hatch weight [2,32], reduced embryo weights [33], and both low and high-temperatures were not significantly different in hatch weight, embryo mortality, and deformed embryos [52]. Meanwhile, high-temperature TM resulted in higher hatchability [36,39], and both low and high-temperature treatments did not impact and significantly differ in hatchability [52,53].…”

“…Meanwhile, high-temperature TM resulted in higher hatchability [36,39], and both low and high-temperature treatments did not impact and significantly differ in hatchability [52,53]. Furthermore, continuous TM was used in most comparative studies [32,33,36,39] compared with intermittent [2,52,53].…”

“…Incubation conditions have a significant effect on hatchability, chick quality and post-hatch performance in chicken. In addition, while the first quarter of incubation is critical to chicken embryogenesis [2], the last quarter is very significant to hatch and post hatch performance [3].…”