Nutritional means to enhance skeletal development in pullets and subsequent effects on layers productivity, bone health and welfare

加拿大供应管理的鸡蛋生产系统有1021个注册鸡蛋农场，总共大约有2000万只鸡蛋，为加拿大的GDP贡献了12.8亿美元。骨骼健康表现为骨质疏松症，是不同饲养系统下蛋鸡的一个长期问题，对鸡群生产力和蛋壳质量以及盈利能力都有不利影响。骨质量受遗传、住房系统环境和营养的影响。然而，在饲料中矿物质含量**没有同时改善的情况下，性成熟程度降低的趋势可能与母鸡用更少的饲料（更多的钙输出和更少的钙输入）生产更多鸡蛋的能力增加并在一起，因此，在饲养和/或产蛋周期中，骨矿化受到损害，导致**死亡率和代谢性钙不足和骨质疏松症引起的发病率。改善母鸡骨骼健康的研究通常集中在控制产蛋期间的环境和营养。然而，随着小鸡在12周龄时发育成熟，在性成熟前后形成髓质骨，在活跃产蛋期间补充钙可能对改善骨密度和质量太晚了。我们的假设是，适当的骨骼发育对于高水平的产蛋率和现代蛋鸡替代住房的挑战至关重要。研究将探讨饲料结构（控制纤维含量和石灰石粒度）和最佳钙、磷和维生素D添加对母鸡骨骼发育仔鸡的作用，以及随后对母鸡生产力、蛋壳质量、宜居性和福利的影响。这是一项及时的研究，将根据加拿大母鸡饲养系统即将发生的变化，为鸡蛋行业提供有价值的信息。该项目将采用各种实验、统计和分析技术，从而为培养高素质人才提供极好的机会。具体而言，该研究项目将支持培养1名博士、2名论文硕士、1名课程硕士、2名本科生、1名博士后和1名技术人员。

Canadian supply managed egg production system has 1,021 registered egg farms with a total of approximately**20 million layers and contributes $1.28B to Canada's GDP. Bone health manifested as osteoporosis is a**persistent problem in layers under different housing systems with detrimental effects on flock productivity and**egg shell quality and thus profitability. Bone quality is influenced by genetics, housing system environment and**nutrition. However, the trends of decreased sexual maturity without concurrent refinement in mineral content**of the feed may juxtapose with the hen's increased capacity to produce more eggs with less feed (more calcium**output and less input) such that bone mineralization is impaired during rearing and /or lay cycle giving rise to**mortality and morbidity stemming from metabolic calcium insufficiency and osteoporosis. Studies to improve**hen skeletal health often focus on manipulating environment and nutrition during the laying. However, as**pullets develop a mature frame size by 12 weeks of age followed by formation of medullary bone around**sexual maturation, supplementing calcium during active lay may be too late to improve bone density and**quality. Our hypothesis is that proper skeletal development is essential for high levels egg production and**challenges of alternative housing for modern layers. Studies will be conducted to investigate the role of feed**structure (manipulation of fiber fraction and limestone particle size) and optimal calcium, phosphorous and**vitamin D supplementation on skeletal development pullets and subsequent effects in productivity, egg shell**quality, livability and welfare in hens. This is a timely research and will provide valuable information to the**egg industry in light of the forthcoming changes in Canadian hen housing systems. The project will employ a**variety of experimental, statistical, and analytical techniques thus providing excellent opportunities for the**training of highly qualified personnel. Specifically, the research project will support training of 1 PhD, 2 MSc**by thesis, 1 MSc by coursework, 2 undergraduate students and 1 Postdoctoral Fellow as well as a technician.