Dusk feeding is practised probably to satisfy the energy requirement during night. However, little is known on the changes with clock gene expressions during this feeding behaviour. In our present study, the linkage of clock gene expressions and feeding behaviour in dusk feeding was investigated in laying hens under two lighting programs: the conventional lighting program (Control) with a light period from 05:00 AM to 21:00 PM and a dark period from 21:00 PM to 05:00 AM; or the shifted lighting program group (SLP) with a light period from 02:00 AM to 18:00 PM and a dark period from 18:00 PM to 02:00 AM. The gene expression-related appetite and circadian rhythm were investigated in hypothalamus and proventriculus at 1, 3 and 5 h before scotophase. The results demonstrated that dusk feeding was synchronously shifted with altered lighting program, dusk feeding was observed from 5 h before scotophase in both groups. The expressions of anorexigenic gene proopiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART) were downregulated (p < 0.05) during dusk feeding and changed in pace with lighting program. The expressions of clock gene period 2 (Per2) and cryptochrome 1 (Cry1) in hypothalamus were downregulated (p < 0.05) during dusk feeding and shifted by lighting program. In the proventriculus, ghrelin expression was decreased (p < 0.05) during dusk feeding by lighting program. In conclusion, the expressions of clock genes Per2 and Cry1 are linked with the downregulated expressions of anorexigenic genes, POMC and CART, and in turn the augmented feed intake at dusk.

中文翻译：

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通过时钟基因的参与，光照程序改变了蛋鸡的黄昏喂食

实行黄昏喂食可能是为了满足夜间的能量需求。然而，在这种进食行为期间，时钟基因表达的变化知之甚少。在我们目前的研究中，在两种光照程序下对蛋鸡进行了黄昏饲养中时钟基因表达和采食行为的联系：常规光照程序（控制），光照时间为上午 05:00 至下午 21:00，以及晚上 21:00 至凌晨 05:00 的黑暗期；或具有从 02:00 AM 到 18:00 PM 的亮时段和从 18:00 PM 到 02:00 AM 的暗时段的移位照明程序组 (SLP)。在暗相前 1、3 和 5 小时，在下丘脑和胃中研究了与基因表达相关的食欲和昼夜节律。结果表明，黄昏喂食与改变的照明程序同步移动，两组均在暗相前 5 小时观察到黄昏摄食。致厌食基因阿黑皮素原的表达（POMC ) 和可卡因和苯丙胺调节的转录本 ( CART  ) 在黄昏喂食期间被下调 ( p < 0.05)，并随着光照程序的变化而变化。下丘脑时钟基因周期2（Per2）和隐花色素1（Cry1）的表达 在黄昏饲养期间下调（p <0.05）并被光照程序改变。在腺胃中， 通过光照程序在黄昏喂养期间ghrelin 表达降低（p < 0.05）。总之，时钟基因Per2和Cry1的表达与厌食基因的下调表达有关，POMC和CART，反过来又增加了黄昏时的采食量。