Agriculture and Agri-Food Canada Research Centre, Agassiz, BC, V0M 1A0 Canada.
Poult Sci. 2012 Jan;91(1):1-7. doi: 10.3382/ps.2011-01453.
The maintenance of bone strength has been an important issue in the debate over cage use for laying hens. Bone strength depends on adequate mechanical load and cages restrict movement. Four laying crosses (Lohmann White, Lohmann Brown, H&N White, and Rhode Island Red × Barred Plymouth Rock cross hens) were housed in conventional cages or in floor pens equipped with perches and nest boxes to measure the effect of the housing system on bone strength. Approximately 15 hens of each genotype from each housing system were killed at 50 wk of age and the radius and tibia of each were removed for analysis. There were no differences between the Lohmann White and H&N White (White Leghorn) hens, likely because of their similar genetic background. The Lohmann Brown and the cross hens (brown-egg layers) were larger and they had heavier bones, but the bone density was not different from that of the other lines. The radius was heavier for hens kept in floor pens than for those kept in cages, but the tibia was not. When hens were kept in floor pens, both bones had greater cortical bone density and cross-sectional area, but the difference between housing systems in cortical bone cross-sectional area was much greater for the radius than it was for the tibia. Although the movement of hens in cages is limited, they spend a great deal of time standing, which puts a mechanical load on the tibia. Hens in floor pens are able to stretch their wings or fly, in contrast to hens kept in cages, which likely explains why the difference between housing systems in cortical bone was greater for the radius than for the tibia.
维持骨骼强度一直是关于笼养产蛋鸡的争论中的一个重要问题。骨骼强度取决于足够的机械负荷，而笼子限制了鸡的活动。本研究选择了 4 个蛋鸡品种（洛曼白、洛曼褐、海兰白和红布罗代尔鸡×斑布罗代尔鸡），分别饲养在传统笼和带栖架和产蛋箱的地面鸡舍中，以测量饲养系统对骨骼强度的影响。每个鸡舍系统的每个基因型约有 15 只母鸡在 50 周龄时被处死，每个鸡的桡骨和胫骨被取出进行分析。洛曼白和海兰白（白来航鸡）母鸡之间没有差异，这可能是因为它们具有相似的遗传背景。洛曼褐和杂交母鸡（褐壳蛋鸡）体型较大，骨骼较重，但骨密度与其他系没有差异。与笼养母鸡相比，地面鸡舍中的母鸡的桡骨更重，但胫骨没有。当母鸡饲养在地面鸡舍时，桡骨和胫骨的皮质骨密度和横截面积都更大，但与笼养相比，地面鸡舍对桡骨皮质骨横截面积的影响要大得多。尽管笼养母鸡的活动受到限制，但它们会花大量时间站立，这会对胫骨造成机械负荷。与笼养母鸡相比，地面鸡舍中的母鸡能够伸展翅膀或飞翔，这可能解释了为什么笼养和地面鸡舍对皮质骨的影响在桡骨上比胫骨上更大。
