Incubation temperature is a crucial environmental factor affecting embryonic development and chick quality. Metabolism during the embryonic stage, particularly liver lipid metabolism, is essential for the growth and development of poultry. This study aimed to investigate the effects of embryo thermal manipulation with high (TMH, 39.5 °C, 65% RH, 8 h/d) and low (TML, 20 °C, 65% RH, 1 h/d) temperatures during 8th to 15th embryonic age on hatching performance and liver lipid metabolism in layer chicks. Additionally, the duration of TM effects was evaluated through a short-term feeding trial. The results indicated that TMH accelerated the hatching process without significantly affecting hatchability and growth performance. In contrast, TML delayed hatching time and significantly reduced hatchability and chick quality. After hatching, TML also increased residual yolk weight and reduced the relative liver weight in relation to body weight and yolk-free body mass. Moreover, lipid droplets in the liver were stained with Oil Red O, and the lipid content in the liver and serum was further detected. TMH had no significant impact on triglyceride (TG) and total-cholesterol (TCHO) content in the liver and serum but upregulated the expression of lipogenesis-related genes ACC, Fas, and Fatp1 compared to the TML group. Conversely, TML significantly reduced liver TG content, enhanced lipoprotein lipase (LPL) activity, and promoted the expression of lipid oxidation-related genes CPT-1, PGC-1α, and PPARα. At 7 d of age, liver LPL activity was significantly increased in the TMH group. However, there were no significant changes in the content of TG and TCHO in the liver and the expression of lipid metabolism-related genes in the TML group. Overall, these results indicate that embryonic TM alters hatching performance and liver lipid metabolism in layer chicks. TML reduces TG content by increasing liver lipid oxidation capacity. However, this effect is not long-lasting, as the influence of TM diminishes as the chicks develop.

中文翻译：

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胚胎热操作改变了孵化后蛋鸡型雏鸡的发育和肝脏脂质代谢


孵化温度是影响胚胎发育和雏鸡质量的关键环境因素。胚胎阶段的新陈代谢，特别是肝脏脂质代谢，对家禽的生长发育至关重要。本研究旨在探讨第 8 至 15 胚胎年龄高温 （TMH， 39.5 °C， 65% RH， 8 h/d） 和低温 （TML， 20 °C， 65% RH， 1 h/d） 胚胎热操作对蛋鸡孵化性能和肝脂质代谢的影响。此外，通过短期喂养试验评估了 TM 效应的持续时间。结果表明，TMH 加速了孵化过程，但对孵化率和生长性能没有显著影响。相比之下，TML 延迟了孵化时间，并显著降低了孵化率和雏鸡质量。孵化后，TML 还增加了残余蛋黄重量，并降低了相对于体重和无蛋黄体重的相对肝脏重量。此外，用油红 O 对肝脏中的脂滴进行染色，进一步检测肝脏和血清中的脂质含量。TMH 对肝脏和血清中的甘油三酯 （TG） 和总胆固醇 （TCHO） 含量没有显著影响，但与 TML 组相比，脂肪生成相关基因 ACC、Fas 和 Fatp1 的表达上调。相反，TML 显著降低肝脏 TG 含量，增强脂蛋白脂肪酶 （LPL） 活性，促进脂质氧化相关基因 CPT-1 、 PGC-1α 和 PPARα 的表达。在 7 d 龄时，TMH 组肝脏 LPL 活性显著增加。然而，TML 组肝脏中 TG 和 TCHO 含量以及脂质代谢相关基因的表达无显著变化。 总体而言，这些结果表明，胚胎 TM 会改变蛋鸡的孵化性能和肝脏脂质代谢。TML 通过增加肝脏脂质氧化能力来降低 TG 含量。然而，这种效果并不持久，因为 TM 的影响会随着雏鸡的发育而减弱。