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Photoperiodic versus metabolic triggers, update on our quest to identify the mediators of sexual maturation in layers

2022 CPRF,Layers
While photoperiod has been generally accepted as the primary if not the exclusive cue to stimulate reproduction in photoperiodic breeders such as laying hen, current knowledge suggests that metabolism can also play an influential role to control the hypothalamic-pituitary gonadal (HPG)-axis. Under commercial settings, photostimulation is used to initiate maturation during the transition from pullet to adult, and we and others have demonstrated this effect is mediated by deep brain photoreceptors located in the medio-basal hypothalamus rather than retinal photoreception. This results in the modulation of hypothalamic neuropeptides delivered to the pituitary gland to ultimately control gonadal functions. However, it is also common to observe pullets entering lay prior to photostimulation, and based on our latest data, this occurs within a narrow body weight window, which appears strain specific, and is dependent on rearing environment. Thus, rather than body weight, we speculate that body composition is responsible for this spontaneous maturation. However, the specific mediators of this metabolic regulation still remain to be determined, and the integration of both photoperiodic and metabolic signals needs to be established. Here, based on ongoing research, we propose that adipose tissue may be a primary source of metabolic markers able to coordinate the neuroendocrine response within the hypothalamus, and regulate follicular maturation, leading to a revision of our current models.
Tags :
mediators,photoperiod,sexual maturation
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University of Guelph

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