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

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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.