This study demonstrates the effects of progesterone on eggshell quality and ultrastructure by injecting progesterone into laying hens 2 and 5 h post-oviposition, respectively. Progesterone injected 2 h post-oviposition (P4-2 h) improved eggshell quality with a significant decrease (P < 0.01) in the thickness of the mammillary layer and a significant increase (P < 0.01) in the thickness of the effective layer in the eggshell ultrastructure compared to the control. Progesterone injected 5 h post-oviposition (P4-5 h) damaged the eggshell quality by significantly reducing (P < 0.01) the effective layer thickness. Progesterone injected delayed obviously (P < 0.01) the following oviposition. Moreover, the concentrations of Thr, Cys, Leu, Lys, and His in the eggshell membranes were significantly higher (P < 0.05) in the P4-2 h treated hens whereas Val and Lys were significantly lower (P < 0.05) in P4-5 h treated hens compared to the control. Therefore, progesterone shows paradoxical effects on eggshell quality depending on the injection time-points post-oviposition, which could explain the contradictions in previous related reports. P4 injected affected the content of amino acids in eggshell membranes, especially lysine which contributed to eggshell quality. In addition, P4 injected 2 h after oviposition improved eggshell quality by promoting the premature fusion of mammillary knobs. This work contributed to a novel insight to understanding the mechanism of improving eggshell quality.

中文翻译：

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黄体酮对蛋鸡蛋壳质量的反常作用。

这项研究通过在产卵后2小时和5小时将黄体酮分别注入蛋鸡，证明了黄体酮对蛋壳质量和超微结构的影响。产后2 h（P4-2 h）注射黄体酮改善了蛋壳质量，乳腺层厚度显着降低（P <0.01），有效层厚度显着增加（P <0.01）。蛋壳的超微结构与对照相比。产后5 h（P4-5 h）注射的黄体酮通过显着降低（P <0.01）有效蛋鸡厚度来损害蛋壳质量。产后注射黄体酮明显延迟（P <0.01）。此外，蛋壳膜中的Thr，Cys，Leu，Lys和His的浓度明显更高（P <0。05）在P4-2 h处理的母鸡中，而Val和Lys在P4-5 h处理的母鸡中显着低于对照组（P <0.05）。因此，黄体酮对卵壳质量显示出反常的作用，这取决于产卵后的注射时间点，这可以解释先前相关报道中的矛盾之处。注射的P4影响蛋壳膜中氨基酸的含量，尤其是赖氨酸，这有助于蛋壳质量。此外，在产卵后2小时注射P4可促进乳头瘤的过早融合，从而改善蛋壳质量。这项工作为了解提高蛋壳质量的机制提供了新颖的见解。孕酮对卵壳质量的显示反常效应，取决于产卵后的注射时间点。这可能解释了先前相关报道中的矛盾之处。注射的P4影响蛋壳膜中氨基酸的含量，尤其是赖氨酸，这有助于蛋壳质量。此外，在产卵后2小时注射P4可促进乳头瘤的过早融合，从而改善蛋壳质量。这项工作为了解提高蛋壳质量的机制提供了新颖的见解。孕酮对卵壳质量的显示反常效应，取决于产卵后的注射时间点。这可能解释了先前相关报道中的矛盾之处。注射的P4影响蛋壳膜中氨基酸的含量，尤其是赖氨酸，这有助于蛋壳质量。此外，在产卵后2小时注射P4可促进乳头瘤的过早融合，从而改善蛋壳质量。这项工作为了解提高蛋壳质量的机制提供了新颖的见解。产后2 h注射P4通过促进乳头瘤的过早融合而改善了蛋壳质量。这项工作为了解提高蛋壳质量的机制提供了新颖的见解。产后2 h注射P4通过促进乳头瘤的过早融合而改善了蛋壳质量。这项工作为了解提高蛋壳质量的机制提供了新颖的见解。