Institute of Animal Science, Agricultural Research Organization, Volcani Center, Rishon Le Tsiyon 7528809, Israel; Faculty of Agriculture Food and Environment, The Hebrew University, Rehovot 76100, Israel.
Institute of Animal Science, Agricultural Research Organization, Volcani Center, Rishon Le Tsiyon 7528809, Israel.
Poult Sci. 2021 Feb;100(2):1192-1204. doi: 10.1016/j.psj.2020.10.068. Epub 2020 Nov 13.
Ambient conditions during chicken embryogenesis, such as insufficient oxygen or changes in temperature, are expected to cause permanent phenotypic changes and affect their posthatch performance. Decades of genetic selection for high growth rate resulted with various physiological and morphological changes that can affect the broiler fitness under environmental stress. To evaluate the selection effect on responses to environmental challenge during embryonic development, and the long-term implications, we have used a unique genetic line, that was not selected for over 30 yr (since 1986), as control for the modern commercial genetic line. At embryonic day 5 (E5), broiler embryos from these 2 genetic lines were divided into 2 treatments: 1) control; 2) 15% O concentration for 12 h/day from E5 through E12 the embryonic period of chorioallantoic membrane formation. Embryos and hatched chicks were characterized for physiological and morphological parameters. Significant differences in relative embryo weight and yolk consumption were found between the 2 lines. The modern line was characterized by a higher metabolic rate and rapid growth, supported by higher hemoglobin levels and hematocrit concentrations, whereas the 1986 line had slower metabolism, lower levels of hematocrit and hemoglobin, higher oxygen volume per 1 g of embryonic tissue indicating higher oxygen availability. Both lines exhibited changes in heart rate, and blood parameters corresponding to cardiovascular system adaptation after hypoxic exposure, seemingly implemented to increase oxygen-carrying capacity to the embryo tissues. Our finding stand in agreement that the genetic selection for high growth rate that led to higher metabolism without a fit of the cardiovascular system, increased the imbalance between oxygen supply and demand.
鸡胚胎发育期间的环境条件，如氧气不足或温度变化，预计会导致永久性的表型变化，并影响它们的孵化后性能。几十年来，为了提高生长速度而进行的遗传选择导致了各种生理和形态变化，这些变化会影响肉鸡在环境压力下的适应能力。为了评估在胚胎发育过程中对环境挑战的选择效应及其长期影响，我们使用了一个独特的遗传系，该遗传系自 1986 年以来（自 1986 年以来）没有经过选择，作为现代商业遗传系的对照。在胚胎第 5 天（E5），来自这 2 个遗传系的肉鸡胚胎被分为 2 个处理：1）对照；2）从 E5 到 E12 每天 12 小时 15%的 O 浓度，这是绒毛尿囊膜形成的胚胎期。对胚胎和孵化小鸡进行了生理和形态参数的特征描述。在这 2 个系之间发现相对胚胎重量和卵黄消耗存在显著差异。现代系的代谢率和生长速度较高，这得益于较高的血红蛋白水平和血细胞比容浓度，而 1986 年的系代谢速度较慢，血细胞比容和血红蛋白水平较低，每克胚胎组织的氧气体积较高，表明氧气供应较高。这两个系的心率和血液参数都发生了变化，这是对低氧暴露后的心血管系统适应的反应，似乎是为了增加胚胎组织的携氧能力。我们的发现与以下观点一致，即高生长速度的遗传选择导致代谢率升高而心血管系统不适应，增加了氧气供应和需求之间的不平衡。
