Has the intensive genetic selection of commercial layer chickens impacted the control of the reproductive axis

在过去的10年里，Bedecarrats博士的研究计划集中在阐明控制家禽繁殖的分子机制。更具体地说，最近的进展导致在鸡的生殖轴的双重控制（刺激/抑制）的表征。这包括识别参与下丘脑控制垂体前叶的受体，沿着它们的信号通路和细胞内相互作用，并表征在生殖周期期间垂体促性腺激素水平上发生的动态变化（从主要抑制性输入转换为刺激性输入）。最近，Bedecarrats博士的团队已经确定了光波长对鸡生殖轴激活的影响，这些结果导致了用于产卵行业的光谱照明LED灯泡的设计，开发和验证。然而，在将基础研究转化为实际应用的同时，我们注意到现代商业蛋鸡品系不再完全符合公认的神经内分泌模型，该模型描述了生殖轴的激活和消退。因此，很可能是为了使每只母鸡的产蛋量翻一番，过去50年来进行的密集遗传选择改变了正常的生殖生理控制。这提出了一些问题，例如，为什么商业层往往成熟没有适当的光刺激？为什么它们会有如此长的产卵期？昼夜节律和排卵过程之间是否存在去周期化？本提案中强调的研究旨在通过比较一种新的实验性来航牛品系（Smoky Joe）与加拿大传统纯系（Donald McQueen Shaver博士，白色来航牛纯系）和现代商业品系来回答这些问题。该方法是首先比较生产参数，并将其与生殖轴内发生的分子事件联系起来。通过识别这些品系之间的差异，结果将首先帮助我们理解负责排卵同步和产蛋持续的实际机制，并将向我们展示密集的遗传选择如何以及在什么水平上影响生殖。最后，了解生理过程的转变将有助于调整和完善农场管理程序，以最好地适应这些新的商业生产线，可能是通过进一步完善照明系统和体重管理。

Over the last 10 years, the research program of Dr. Bedecarrats focused on elucidating the molecular mechanisms controlling reproduction in poultry. More specifically, recent advances resulted in the characterisation of the dual control (stimulatory/inhibitory) of the reproductive axis in chickens. This included identifying the receptors involved in the hypothalamic control of the anterior pituitary gland along with their signaling pathways and intracellular interactions, and characterizing the dynamic changes occurring at the level of the pituitary gonadotropes during a reproductive cycle (switch from a primarily inhibitory to a stimulatory input). More recently, the team of Dr. Bedecarrats has characterized the effect of light wavelength on the activation of the reproductive axis in chickens, and these results have led to the design, development and validation of a spectrum lighting LED bulb for the egg-laying industry. However, while translating basic research into practical applications, we noticed that modern commercial strains of laying hens no longer fully fit the accepted neuroendocrine models describing the activation and regression of the reproductive axis. Thus, it is likely that in an effort to double the number of eggs laid per hen, the intensive genetic selection performed over the last 50 years has altered the normal physiological control of reproduction. This raises a number of questions such as, why do commercial layers tend to mature without proper photostimulation? Why do they display such extended laying persistency? Is there a desynchronization between the circadian rhythm and the ovulatory process? The research highlighted in this proposal will aim at answering these questions by comparing an unselected experimental strain of Leghorn (Smoky Joe) with a Canadian heritage pure lines (Dr. Donald McQueen Shaver, White Leghorn pure line) and modern commercial strains. The approach is to first compare production parameters and relate these to molecular events occurring within the reproductive axis. By identifying the differences between these strains, results will first help us understand the actual mechanisms responsible for the synchronization of ovulation and the persistency of lay, and will show us how and at what level of the axis the intensive genetic selection impacted reproduction. Finally, understanding the shift in physiological processes will help adjust and refine on-farm management procedures to best accommodate these new commercial lines, possibly by further refining lighting systems and body weight management.