Thermal manipulation modifies embryonic growth, hepatic free amino acid concentrations, and hatching performance in layer-type chicks

Abstract

Thermal manipulation (TM) of incubation temperature has been demonstrated to alter metabolism and post-hatch thermotolerance in broiler strains (meat-type chickens). Fewer reports were focused on layer-type chickens and there was no report on amino acid metabolism during TM in layer-type embryos. In this study, we investigated the effects of TM on embryonic development, hepatic amino acid metabolism, and hatching performance in layer-type chickens. Fertilized eggs were incubated under control thermoneutral temperature (CT, 37.6°C) and TM with high temperature (TMH, 39°C, 8 h/day) or low temperature (TML, 20°C, 1 h/day) from embryonic day (ED) 8 to ED 15. The embryonic weight and relative embryonic weight (yolk-free embryonic weight to the initial egg weight) significantly declined in the TML group at ED 13 (P < 0.01) and ED 16 (P < 0.0001), and were significantly increased (P < 0.001) in the TMH group at ED 16, in comparison with the embryos in the CT group. The concentrations of all hepatic free amino acids were significantly increased (P < 0.01) with embryonic development. Interestingly, TMH and TML caused similar effects on hepatic amino acid metabolism, in which most of the essential and non-essential amino acids were significantly declined (P < 0.05) under TM treatments at ED 13 but not affected at ED 16. Until hatching, TML, but not TMH, caused a significant (P < 0.05) delay (31–38 min/day from ED 8) in incubation duration. The hatchability in the TML group was lower than the other two groups, which indicated that 20°C as cold stimulation was not suitable for layer embryos. The body weight, yolk weight, yolk-free body mass, and chick quality were not affected by TM treatments. However, the relative weight of the liver, but not the heart, was significantly reduced (P < 0.05) at hatching by TML treatment. In conclusion, TML, but not TMH, caused to delay in embryogenesis and affected the internal organ of chicks at hatch. Similar changes in amino acid metabolism under TMH and TML indicated that thermal stress induced by both high and low extreme ambient temperatures influences embryonic amino acid metabolism in a similar fashion in layer-type embryos.

Effect of thermal manipulation on embryonic development, hatching process, and chick quality under heat-stress conditions

“…Incubation conditions have a substantial impact on embryonic development, hatchability, chick quality, and posthatch performance ( Han et al, 2022 ; Rocha et al, 2022 ; Fares et al, 2023 ; Al-Zghoul et al, 2023 ). Hatchability and chick quality are 2 crucial factors that determine the success of a hatchery ( Yassin et al, 2008 ).…”

“…Hatchability and chick quality are 2 crucial factors that determine the success of a hatchery ( Yassin et al, 2008 ). Several studies have been conducted to discover strategies to improve these factors, and one of the most effective methods is temperature manipulation ( Han et al, 2022 ; Rocha et al, 2022 ; Tona et al, 2022 ; Al-Zghoul et al, 2023 ). They demonstrated that by controlling the temperature during incubation, it is possible to boost the hatchability percentage and chick quality by improving the embryo's physiological and biological functions.…”

“…Temperature, as an important environmental condition that impacts several biological functions and behavioral activities of birds, is considered the most critical incubation condition ( Han et al, 2022 ; Rocha et al, 2022 ; Yalcin et al, 2022 ). Piestun et al (2015) , Al-Zghoul and El-Bahr (2019) , and Han et al (2022) have shown that controlling the temperature during incubation can influence embryonic organ development, hatching parameters, and chick quality at the hatch. Finding the optimal temperature range and exposure period is crucial, and it depends on the specific poultry breed.…”

“…By optimizing the temperature conditions during incubation, hatcheries can produce healthier, more robust chicks that are better suited for commercial production. Furthermore, chicks incubated in a manipulating temperature range have a higher growth rate and thermal tolerance, as well as a stronger immune system and a reduced mortality rate ( Liu et al, 2015 ; Ismail et al, 2016 ; Al-Zghoul and El-Bahr, 2019 ; Han et al, 2022 ; Ramiah et al, 2022 ; Rocha et al, 2022 ). Thermal manipulation during chicken egg incubation has been demonstrated to significantly improve birds’ metabolism, posthatch thermoregulation, and reduce the adverse effect of high ambient temperature ( Han et al, 2022 ; Ramiah et al, 2022 ).…”

“…Furthermore, chicks incubated in a manipulating temperature range have a higher growth rate and thermal tolerance, as well as a stronger immune system and a reduced mortality rate ( Liu et al, 2015 ; Ismail et al, 2016 ; Al-Zghoul and El-Bahr, 2019 ; Han et al, 2022 ; Ramiah et al, 2022 ; Rocha et al, 2022 ). Thermal manipulation during chicken egg incubation has been demonstrated to significantly improve birds’ metabolism, posthatch thermoregulation, and reduce the adverse effect of high ambient temperature ( Han et al, 2022 ; Ramiah et al, 2022 ). In addition, it can positively affect birds' development, productivity, and welfare ( Loyau et al, 2016 ; Vinoth et al, 2018 ; Garvalho et al, 2020 ; Al-Zghoul et al, 2023 ).…”