Agricultural Research Organization, Volcani Center, Department of Poultry and Aquaculture Science, Rishon LeTsiyon, Israel.
Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Poult Sci. 2018 Apr 1;97(4):1429-1440. doi: 10.3382/ps/pex393.
Storing eggs at low temperature prior to incubation is common practice in the broiler hatchery industry; however, prolonged storage (beyond 7 d) is known to increase early embryonic mortality and reduce chick quality and performance. To better understand the basis of this mortality, we previously published milestone criteria to evaluate morphological and cellular properties of the freshly laid embryo. Using these criteria, in the present study we checked the effects of storage at 18°C and 12°C for up to 28 d on hatchability and chick quality. Furthermore, using a 3D high-resolution episcopic microscopy (HREM) imaging system combined with standard and confocal microscopy and cell viability markers, we analyzed the effects of the different storage conditions on embryonic developmental stage, cytoarchitectural properties, mitotic index and cell survival. A total of 1,483 eggs from a young flock were divided in 2 groups, 18°C and 12°C, and stored for 7, 14, 21, and 28 d. Following storage, randomly selected 1,222 eggs were incubated, and the hatched chicks were evaluated for chick quality parameters. Nonhatched eggs were also analyzed to determine the stage of embryonic mortality. The remaining 261 eggs were isolated and analyzed for developmental stage, cytoarchitecture, mitotic index, and cell death following storage. Hatchability rates beyond 7 d of storage at 12°C were significantly improved compared to 18°C, and chick quality remained high. Similar results were obtained for an old flock's eggs (n = 1,350). Analyzing the embryos, at each time point, we found that at 12°C, the developmental progression during storage slows significantly, mitotic index-which at this temperature may indicate mitotic arrest-increases and the rate of early apoptosis is half than at 18°C. Moreover, the HREM system and histological sections showed that embryos stored at 18°C for prolonged times undergo dramatic cytoarchitectural changes that may be maladaptive to resuming normal development after diapause. We thus demonstrate the usefulness of the milestone criteria for predicting and studying the storage conditions that will allow for better performance in hatchery practice.
在孵化前将鸡蛋低温储存是肉鸡孵化场行业的常见做法；然而，长时间储存（超过 7 天）已知会增加早期胚胎死亡率，并降低雏鸡质量和性能。为了更好地了解这种死亡率的基础，我们之前发布了里程碑标准来评估刚产下的胚胎的形态和细胞特性。使用这些标准，在本研究中，我们检查了在 18°C 和 12°C 下储存长达 28 天对孵化率和雏鸡质量的影响。此外，使用 3D 高分辨率透视显微镜（HREM）成像系统结合标准和共聚焦显微镜以及细胞活力标志物，我们分析了不同储存条件对胚胎发育阶段、细胞结构特性、有丝分裂指数和细胞存活的影响。总共从一个年轻鸡群中分离出 1483 个鸡蛋，分为 18°C 和 12°C 两组，分别储存 7、14、21 和 28 天。储存后，随机选择 1222 个鸡蛋进行孵化，并评估孵化出的雏鸡的雏鸡质量参数。未孵化的鸡蛋也进行了分析，以确定胚胎死亡率的阶段。其余 261 个鸡蛋被分离出来，并在储存后分析其发育阶段、细胞结构、有丝分裂指数和细胞死亡。在 12°C 下储存超过 7 天的孵化率明显高于 18°C，并且雏鸡质量保持较高水平。来自旧鸡群的鸡蛋（n=1350）也获得了类似的结果。在每个时间点分析胚胎时，我们发现 12°C 下，储存过程中的发育进展明显减缓，有丝分裂指数——在这个温度下可能表示有丝分裂停滞——增加，早期细胞凋亡率是 18°C 的一半。此外，HREM 系统和组织学切片显示，在 18°C 下长时间储存的胚胎会发生剧烈的细胞结构变化，这可能不利于在滞育后恢复正常发育。因此，我们证明了里程碑标准在预测和研究允许在孵化场实践中更好表现的储存条件方面的有用性。
