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

加拿大供应管理鸡蛋生产系统拥有1021个注册鸡蛋养殖场，总计约2000万只蛋鸡，为加拿大国内生产总值贡献了12.8亿美元。表现为骨质疏松症的骨骼健康是不同住房制度下蛋鸡的一个**持续性问题，对鸡群生产力和蛋壳质量造成不利影响，从而影响盈利能力。骨骼质量受遗传、住房系统环境和营养的影响。然而，在饲料矿物质含量**没有同时精炼的情况下，性成熟度下降的趋势可能与母鸡用更少的饲料生产更多的鸡蛋(更多的钙输出和更少的投入)的能力增加并列在一起，从而在饲养和/或产蛋周期中骨骼矿化受到损害，导致**由于代谢性钙不足和骨质疏松症而导致的死亡率和发病率。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上。然而，随着小鸡在12周龄时发育成成熟的框架尺寸，随后在性成熟前后形成髓质骨，在活跃的产蛋期补充钙可能太晚了，无法提高骨密度和质量。我们的假设是，适当的骨骼发育对于高水平的鸡蛋生产和现代蛋鸡替代住房的挑战至关重要。将研究饲料结构(控制纤维含量和石灰石颗粒大小)和钙、磷和维生素D的最佳添加对母鸡骨骼发育小鸡的作用，以及随后对母鸡生产力、蛋壳质量、存活率和福利的影响。这是一项及时的研究，鉴于加拿大鸡舍系统即将发生的变化，这将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**培训高素质人员提供极好的机会。具体来说，该研究项目将支持1名博士、2名硕士论文、1名硕士课程、2名本科生和1名博士后研究员以及1名技术员的培训。

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.