Influence of an alimentary supplementation with 25-hydroxycholecalciferol on ovine calcium homeostasis

围产期低钙血症是奶牛的常见问题。虽然低钙动物并不总是出现临床乳热，但血浆钙浓度的短暂下降使动物容易出现各种健康问题和疾病。最近，我们的团队可以证明口服补充维生素D代谢物25-羟基胆钙化醇可能是稳定围膜钙稳态的一个有前途的概念。由于上述研究是在一个商业奶牛群中进行的，表征所观察到的生理效应的机制的设施有限。在此提交的项目旨在确定25-羟基胆骨化醇对胃肠道、肾脏和骨骼的影响，这些器官对钙稳态的调节至关重要。绵羊将被用作研究的动物模型，包括体内平衡研究以及专注于上皮和细胞水平的功能和结构研究。利用在标准化条件下进行的动物实验，我们希望验证我们对25-羟基胆骨化醇的假设作用的假设，以便获得必要的基本信息，以发展一个稳定奶牛围膜大矿物质稳态的创新概念。

Peripartal hypocalcemia is a common problem in dairy cows. Although hypocalcemic animals do not always develop clinical milk fever, the transient decrease in plasma calcium concentration predisposes the animals towards various health problems and diseases. Recently, our group could demonstrate that the oral supplementation with the vitamin D metabolite 25-hydroxycholecalciferol could be a promising concept to stabilize peripartal calcium homeostasis. As the mentioned study was carried out in a commercial dairy herd, the facilities to characterize the mechanisms mediating the observed physiological effects were limited. The herewith submitted project is designed to determine the effects of 25-hydroxycholecalciferol on the gastrointestinal tract, the kidney and the skeleton, the organs which are crucial for the regulation of calcium homeostasis. Sheep will be used as an animal model for the investigations which include in vivo-balance studies as well as functional and structural studies focusing on the epithelial and cellular level. Taking advantage of an animal experiment carried out under standardized conditions we hope to verify our hypotheses on the putative effects of 25-hydroxycholecalciferol in order to obtain basic information necessary to develop an innovative concept to stabilize peripartal macromineral homeostasis in dairy cows.