Use of full-body imaging scans on live chickens to develop a model describing the impact of body composition on sexual maturation

鸡是季节性繁殖者，依靠光周期（白天长度）的变化来开始和结束繁殖。这已被行业广泛用于允许全年产卵，然而，我们最近的数据表明，在现代蛋鸡中，代谢信号可能比光周期信号更重要，这导致了一个修订的一般假设，即代谢信号，特别是来自脂质和脂肪组织的信号，可以覆盖和/或干扰下丘脑-垂体-性腺轴的成熟。因此，育雏过程中体成分的变化不仅直接影响到雏鸡的健康和福利，而且对未来的产蛋量也有直接影响。我们正在进行的研究重点是确定介导代谢状态的特定标记物。然而，缺乏一种非侵入性的分析平台来跟踪小鸡生长过程中身体成分的动态变化，目前的方法依赖于对尸体而不是活体动物的分析。因此，我们建议首先建立活鸡全身成像扫描的标准操作程序，然后利用该平台跟踪小鸡体内成分和生理状态的动态变化，以便更好地将脂肪积累与性成熟联系起来。最后，数据将用于开发一个模型，该模型精确描述了控制身体成分对蛋鸡繁殖能力和健康的影响的过程。反过来，该模型将提供预测小鸡生长和成熟的工具，并主动实施农场管理调整，以确保满足小鸡生长期间的需求（无论饲养环境如何），并减少饲料浪费和相关成本。此外，了解代谢状态的动态变化，特别是脂肪积累如何影响卵巢功能，将有助于制定策略，减少商业品种鸡的生殖（和代谢）失调，包括脂肪肝综合征、骨骼虚弱和缺钙。

Chickens are seasonal breeders which rely on changes in photoperiod (daytime length) to initiate and terminate reproduction. This has been used extensively by the industry to allow for egg production all year long, however, our recent data suggest that metabolic cues may be more important than photoperiodic signals in modern layers, leading to a revised general hypothesis that metabolic signals, specifically from lipids and adipose tissue, can override and/or interfere with the maturation of the hypothalamic pituitary gonadal axis. Hence, changes in body composition during pullet rearing have a direct impact not only on health and welfare, but also on future egg production. Our ongoing research focuses on identifying the specific markers mediating metabolic status. However, a non-invasive analytical platform to follow the dynamic changes in body composition during pullet growth is lacking and current approaches rely on analyses of carcasses rather than live animals. Thus, we propose to first establish a Standard Operating Procedure for the use of full-body imaging scans on live chickens, then use this platform to follow the dynamic changes in body composition and physiological status in pullets to better link fat accumulation and sexual maturation. Finally, data will be used to develop a model that precisely describes the processes governing the impact of body composition on reproductive capacity and fitness of layers. In turn, this model will provide the tool to predict growth and maturation of pullets and proactively implement on-farm adjustment in management to ensure requirements are met during pullet growth (regardless of rearing environment) and reduce feed wastage and associated costs. Furthermore, understanding how dynamic changes in metabolic status, especially fat accumulation, impact the ovarian function will help elaborate strategies to reduce reproductive (and metabolic) dysregulation in commercial strains of chickens, including fatty liver syndrome, skeletal weakness and calcium deficiency.