Assessing Differences in the Quality Properties and Ultrastructure of Eggshell as Affected by Chicken Strain and Flock Age During Incubation Period

ABSTRACT Three hundred hatching eggs from two layer breeder flocks (Hy-Line Brown and hy-Line W-36; 150 each) were obtained at three different periods of laying cycle (early, middle and late stages). The hatching eggs were randomly taken to assess the impact of chicken strain, age, and hatching time on some eggshell measurements and structures. Results indicate that egg weight, shell percentage and shell thickness were significantly affected by strain, breeder age, and incubation time. Increasing rate of calcium absorption and utilization by the embryos during the embryonic stage clearly reflects the decrease occurred in eggshell strength. The differences of eggshell breaking strength during incubation time periods were 0.41 and 0.55 kg/cm2, the differences due to the incubation time may be due to the higher demand for calcium utilization in the late incubation period (18 days), observed on the10th day of incubation. Brown eggs recorded significant higher calcium percentage in eggshell compared to the white ones. The brown breeder hens recorded significant higher total pores per egg compared to the white egg. Concerning eggshell ultrastructure, total thickness of the brown eggshell was significantly higher than those of the white eggshell by about 3.7%. All parameters, except for total thickness, were significantly affected by the interaction between strain and breeder age. Finally, we conclude that some traits including egg weight, shell percentage, shell thickness, calcium percentages in eggshell, and total pores per egg were significantly affected by strain, breeder age, and incubation time. Eggshell ultrastructure of brown egg was better compared to the white ones.

摘要
本研究从两个蛋种鸡群（海兰褐（Hy-Line Brown）与海兰W-36（Hy-Line W-36））各采集150枚孵化用种蛋，共计300枚，采样覆盖产蛋周期的三个阶段：早期、中期与晚期。本研究随机选取该批种蛋，以探究鸡品系、种鸡日龄及孵化时长对若干蛋壳指标与结构的影响。
结果显示，蛋重、蛋壳占比及蛋壳厚度均显著受鸡品系、种鸡日龄与孵化时长的影响。胚胎在胚胎发育阶段对钙的吸收与利用速率升高，可显著反映蛋壳强度的下降。不同孵化时段的蛋壳抗破强度差值为0.41与0.55 kg/cm²；该由孵化时长引发的差异，或归因于孵化后期（第18天）更高的钙利用需求，该现象在孵化第10天即可观测到。
褐壳蛋的蛋壳钙占比显著高于白壳蛋；海兰褐种鸡所产种蛋的单蛋总孔隙数显著多于白壳蛋。关于蛋壳超微结构，褐壳蛋的总蛋壳厚度较白壳蛋高出约3.7%。
除总蛋壳厚度外，其余所有指标均显著受鸡品系与种鸡日龄的交互作用影响。最后本研究得出结论：蛋重、蛋壳占比、蛋壳厚度、蛋壳钙占比及单蛋总孔隙数等性状，均显著受鸡品系、种鸡日龄及孵化时长的影响；褐壳蛋的蛋壳超微结构优于白壳蛋。