Institute of Animal Science, Guangdong Academy of Agricultural Sciences, Key Laboratory of Animal Nutrition and Feed Science (South China) of Ministry of Agriculture, State Key Laboratory of Livestock and Poultry Breeding, Guangdong Public Laboratory of Animal Breeding and Nutrition, Guangdong Key Laboratory of Animal Breeding and Nutrition, Guangzhou, 510640, China.
Institute of Animal Science, Guangdong Academy of Agricultural Sciences, Key Laboratory of Animal Nutrition and Feed Science (South China) of Ministry of Agriculture, State Key Laboratory of Livestock and Poultry Breeding, Guangdong Public Laboratory of Animal Breeding and Nutrition, Guangdong Key Laboratory of Animal Breeding and Nutrition, Guangzhou, 510640, China.
Poult Sci. 2022 Feb;101(2):101573. doi: 10.1016/j.psj.2021.101573. Epub 2021 Oct 29.
This study evaluated the changes in eggshell mechanical properties, ultrastructure, calcium metabolism-related serum indices, and gene expression in eggshell gland during eggshell formation between laying ducks in the peak (young duck) and late phase (aged duck) of production. A total of 84 healthy young (31 wk of age) and 84 healthy aged (65 wk of age) Longyan laying ducks were each divided into 6 replicates of 14 birds, and caged individually. All the ducks were fed in one house with the same corn-soybean meal-based diet for 5 wk. The eggshell mechanical properties (shell proportion, thickness, breaking strength, and fracture toughness) and chemical components (matrix proteins, calcium, phosphorus, and magnesium) decreased in aged laying ducks (P < 0.05). Shell structural indices: total thickness, effective thickness and its proportion decreased, whereas mammillary knob width and its proportion increased (P < 0.05). The regulation values of early fusion, cuffing, caps, and total score of mammillary knobs were higher in aged laying ducks relative to the young ducks (P < 0.05). During the initial, growth and terminal stages of eggshell formation, shell thickness and breaking strength (terminal), shell weight, and its proportion (terminal) decreased in aged laying ducks (P < 0.05). Ultrastructural changes during shell formation indicated that the mammillary-knob density and effective thickness decreased (P < 0.05). Decreases occurred in serum content of phosphorus (growth), and estradiol and calcium contents (terminal) (P < 0.05). Relative expression of Ca transporter and HCO exchanger, and matrix proteins genes decreased in aged laying ducks (P < 0.05) at all stages of eggshell formation. Collectively, the decreased incidence of early fusion and caps, increased thickness and width of mammillary knobs, and decreased effective thickness are the crucial differences leading to the compromised mechanical properties of eggshell in the late laying period. A disturbed regulation of calcium metabolism and uterine expression of ion transporters, especially for HCO exchange of aged laying ducks likely contribute to age-induced ultrastructural deterioration of the eggshell.
本研究评估了产蛋高峰期（青年鸭）和后期（老年鸭）产蛋鸭蛋壳形成过程中蛋壳机械性能、超微结构、钙代谢相关血清指标和蛋壳腺基因表达的变化。将 84 只健康的青年鸭（31 周龄）和 84 只健康的老年鸭（65 周龄）分为 6 个重复，每个重复 14 只鸭，单独笼养。所有的鸭子都在同一个房子里用相同的玉米-豆粕基础日粮喂养 5 周。与青年鸭相比，老年鸭的蛋壳机械性能（蛋壳比例、厚度、断裂强度和断裂韧性）和化学成分（基质蛋白、钙、磷和镁）降低（P<0.05）。蛋壳结构指标：总厚度、有效厚度及其比例降低，而乳突宽度及其比例增加（P<0.05）。老年鸭的早期融合、套环、帽和乳突总评分的调节值高于青年鸭（P<0.05）。在蛋壳形成的初始、生长和终末阶段，老年鸭的蛋壳厚度和断裂强度（终末）、蛋壳重量及其比例（终末）降低（P<0.05）。蛋壳形成过程中的超微结构变化表明乳突密度和有效厚度降低（P<0.05）。生长阶段血清磷含量降低，终末阶段雌二醇和钙含量降低（P<0.05）。在蛋壳形成的各个阶段，老年鸭的 Ca 转运体和 HCO 交换体以及基质蛋白基因的相对表达降低（P<0.05）。总之，早期融合和帽发生率降低，乳突厚度和宽度增加，有效厚度降低，是导致后期产蛋蛋壳机械性能下降的关键差异。钙代谢和子宫离子转运体表达的紊乱，特别是老年鸭的 HCO 交换紊乱，可能导致蛋壳超微结构的年龄相关性恶化。
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