Over the last few decades, there has been an increasing demand for poultry meat as a source of high-quality protein for human consumption. To meet this demand, the poultry industry employed planned genetic selection targeting higher feed efficiency and performance. In addition to maximizing body weight, there has been a considerable shortening in the growing period. In effect, in modern broilers, the period of embryonic and neonatal development represents almost half of its productive lifespan. Particularly, the perinatal and immediate postnatal period is a crucial time in the development of the young chick influencing quality broiler performance at marketing. Consequently, any approach that supports embryonic and neonatal growth is expected to have a significant effect on overall health and performance of broiler chicken. In this regard, probiotics are widely used as growth promoters in the poultry industry. However, probiotic application is limited to in-feed supplementation post-hatch and their effect on embryonic growth has not been studied. Moreover, poultry researchers have now realized that future gains in production potential of these birds will come from advancements made on embryogenesis during incubation. Therefore, given their beneficial attributes, in-ovo supplementation of probiotics, could be a potential and viable approach to support perinatal and neonatal growth thereby enabling the chicken to better express its genetic potential. Hence, the overall goal of this study is to elucidate the effect of in-ovo probiotic supplementation on the energy status, intestinal development and microbiome acquisition in the growing embryo and chicksThe specific objectives of this study are:1. To determine the effect of in-ovo probiotic supplementation on energy status of perinatal broiler embryos, hatchlings and chicks2. To determine the effect of in-ovo probiotic supplementation on the structure and function of the yolk sac membrane (YSM) and small intestine (jejunum) in broiler embryos and chicks3. Identify the effect of in-ovo probiotic supplementation on the composition and diversity of the gut (cecal) microbiome of the growing embryo and broiler chicks.