Study of the impact of hypothalamic factors on reproduction in poultry

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In most avian species, changes in photoperiod are required for successful reproduction. In poultry, photostimulation results in the activation of the hypothalamo-pituitary-gonadal axis with an increase in gonadotropin releasing hormone (GnRH), luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion. After reaching a peak in egg production, hens progressively cease laying and enter either a photorefractory stage or express incubation behaviour. In addition to this established stimulatory pathway involving GnRH, a potential inhibitory pathway involving a gonadotropin inhibiting hormone (GnIH) has also been proposed. We have recently shown that the gene expression of both GnRH and GnIH receptors fluctuate during a reproductive cycle, and that their mRNA levels are inversely correlated in chickens. However, the exact molecular mechanisms involved in the control of these neuroendocrine pathways still remain to be determined. This is of critical importance since the duration of an egg-laying period in females, and fertility in males are two corner stones of a successful poultry industry. Thus, this project aims at optimizing existing procedures and developing new tools for reproductive technologies of the future. New knowledge will be acquired by studying the mechanisms of action of both GnRH and GnIH in vivo as well as in vitro, and optimization of existing management procedures will be achieved by studying the effects of various photostimulation paradigms on the reproductive axis in a strain of genetically blind chickens we recently established at the University of Guelph. As a result, the proposed research will help strengthen the poultry industry at both a regional (Ontario) and national (Canada) level. Furthermore, research will be performed by graduate students, thus contributing to the training of highly qualified personel.