Fu Yu, Zhou Jianmin, Schroyen Martine, Zhang Haijun, Wu Shugeng, Qi Guanghai, Wang Jing
Key Laboratory of Feed Biotechnology, Ministry of Agriculture and Rural Affairs, Institute of Feed Research, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Precision Livestock and Nutrition Laboratory, Gembloux Agro-Bio Tech, TERRA Teaching and Research Centre, University of Liège, Gembloux, B-5030, Belgium.
J Anim Sci Biotechnol. 2024 Mar 4;15(1):37. doi: 10.1186/s40104-023-00986-2.
Deteriorations in eggshell and bone quality are major challenges in aged laying hens. This study compared the differences of eggshell quality, bone parameters and their correlations as well as uterine physiological characteristics and the bone remodeling processes of hens laying eggs of different eggshell breaking strength to explore the mechanism of eggshell and bone quality reduction and their interaction. A total of 240 74-week-old Hy-line Brown laying hens were selected and allocated to a high (HBS, 44.83 ± 1.31 N) or low (LBS, 24.43 ± 0.57 N) eggshell breaking strength group.
A decreased thickness, weight and weight ratio of eggshells were observed in the LBS, accompanied with ultrastructural deterioration and total Ca reduction. Bone quality was negatively correlated with eggshell quality, marked with enhanced structures and increased components in the LBS. In the LBS, the mammillary knobs and effective layer grew slowly. At the initiation stage of eggshell calcification, a total of 130 differentially expressed genes (DEGs, 122 upregulated and 8 downregulated) were identified in the uterus of hens in the LBS relative to those in the HBS. These DEGs were relevant to apoptosis due to the cellular Ca overload. Higher values of p62 protein level, caspase-8 activity, Bax protein expression and lower values of Bcl protein expression and Bcl/Bax ratio were seen in the LBS. TUNEL assay and hematoxylin-eosin staining showed a significant increase in TUNEL-positive cells and tissue damages in the uterus of the LBS. Although few DEGs were identified at the growth stage, similar uterine tissue damages were also observed in the LBS. The expressions of runt-related transcription factor 2 and osteocalcin were upregulated in humeri of the LBS. Enlarged diameter and more structural damages of endocortical bones and decreased ash were observed in femurs of the HBS.
The lower eggshell breaking strength may be attributed to a declined Ca transport due to uterine tissue damages, which could affect eggshell calcification and lead to a weak ultrastructure. Impaired uterine Ca transport may result in reduced femoral bone resorption and increased humeral bone formation to maintain a higher mineral and bone quality in the LBS.
蛋壳和骨骼质量下降是老龄蛋鸡面临的主要挑战。本研究比较了不同蛋壳破损强度蛋鸡的蛋壳质量、骨骼参数及其相关性，以及子宫生理特征和骨重塑过程，以探讨蛋壳和骨骼质量下降的机制及其相互作用。选取240只74周龄海兰褐蛋鸡，分为高蛋壳破损强度组（HBS，44.83±1.31 N）和低蛋壳破损强度组（LBS，24.43±0.57 N）。
LBS组蛋壳厚度、重量和重量比降低，伴有超微结构恶化和总钙含量降低。骨骼质量与蛋壳质量呈负相关，LBS组骨骼结构增强，成分增加。在LBS组中，乳头瘤和有效层生长缓慢。在蛋壳钙化起始阶段，相对于HBS组，LBS组蛋鸡子宫中总共鉴定出130个差异表达基因（DEGs，122个上调，8个下调）。这些DEGs与细胞钙超载导致的细胞凋亡有关。LBS组中p62蛋白水平、半胱天冬酶-8活性、Bax蛋白表达较高，Bcl蛋白表达和Bcl/Bax比值较低。TUNEL检测和苏木精-伊红染色显示，LBS组蛋鸡子宫中TUNEL阳性细胞显著增加，组织损伤明显。虽然在生长阶段鉴定出的DEGs较少，但LBS组也观察到类似的子宫组织损伤。LBS组肱骨中与矮小相关转录因子2和骨钙素的表达上调。HBS组股骨内皮质骨直径增大，结构损伤增多，灰分降低。
较低的蛋壳破损强度可能归因于子宫组织损伤导致的钙转运下降，这可能影响蛋壳钙化并导致超微结构薄弱。子宫钙转运受损可能导致股骨骨吸收减少，肱骨骨形成增加，以维持LBS组较高的矿物质和骨骼质量。
