Millam J R, Kridis M, Vohra P
Br Poult Sci. 1986 Mar;27(1):83-91. doi: 10.1080/00071668608416857.
White Leghorn hens were fed either a conventional diet containing 40 gCa/kg from oyster shell, or one low in Ca (3 g/kg) with oyster shell offered separately. In experiment 1 access to oyster shell was unrestricted; in experiment 2. Access was time-restricted to the first 6 h of the photophase of the 14L:10D photoperiod. Irrespective of time-restriction, hens offered oyster shell laid heavier eggs, but shell thickness was reduced. On days on which only ovulation occurred, time-restricted hens consumed significantly less Ca than unrestricted hens. In contrast, on days on which only oviposition occurred, time-restricted hens consumed significantly more Ca than unrestricted hens. These results suggest that when access to oyster shell is time-restricted to morning hours Ca consumption occurs in response to a Ca deficit persisting from the previous period of shell calcification.
白来航母鸡被喂食两种饲料，一种是含有每千克40克钙（来自牡蛎壳）的传统饲料，另一种是钙含量低（每千克3克）的饲料，同时单独提供牡蛎壳。在实验1中，母鸡可自由获取牡蛎壳；在实验2中，获取牡蛎壳的时间被限制在14小时光照：10小时黑暗光周期的光照阶段的前6小时。无论是否有时间限制，提供牡蛎壳的母鸡所产鸡蛋更重，但蛋壳厚度会降低。在仅发生排卵的日子里，有时间限制的母鸡比无时间限制的母鸡消耗的钙显著更少。相反，在仅发生产蛋的日子里，有时间限制的母鸡比无时间限制的母鸡消耗的钙显著更多。这些结果表明，当获取牡蛎壳的时间被限制在上午时段时，钙的消耗是对前一阶段蛋壳钙化持续存在的钙缺乏做出的反应。
