The effects of subclinical hypocalcemia have been explored in numerous observational and mechanistic studies in recent years. Besides obvious, well-known effects on muscle contractility, the role of Ca with respect to immune function and intermediary metabolism explains the contribution of subclinical hypocalcemia to the development of several diseases observed in early lactation and underlines its importance in high-performing dairy cows. The present review aims at integrating recent scientific progress, such as discoveries about the role of the mammary gland in regulating bone mobilization, into generally accepted aspects of the endocrine control of Ca homeostasis. We will discuss Ca transport mechanisms through absorption, resorption, secretion, and mobilization, as well as the physiological regulation of Ca through parathyroid hormone, 1,25-dihydroxyvitamin D, fibroblast growth factor 23, and serotonin, in addition to dietary mineral requirements. To improve hypocalcemia prevention strategies, our knowledge of the physiological mechanisms necessary to maintain normocalcemia and their endogenous regulation should be combined with data derived from herd-level studies. Using such studies, we will discuss prepartum nutritional strategies aimed at reducing the incidence of subclinical hypocalcemia, as well as options for postpartum Ca supplementation and their effects on early-lactation health and production. Especially in respect to approaches that might interfere with endogenous adaptation processes, such as supplementation with vitamin D metabolites or large doses of Ca, a thorough understanding of the underlying mechanisms that might induce unwanted hypocalcemia rebound effects will be crucial to ameliorate our future management of transition cows. Continued efforts by researchers to understand the interaction of Ca homeostasis with prevention strategies is necessary to optimize cow health and support copious milk production.

中文翻译：

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专题讨论会回顾：奶牛钙动态平衡-低钙血症对健康的影响及预防策略。

近年来，在许多观察和机制研究中已经探索了亚临床低钙血症的作用。除了对肌肉收缩的明显，众所周知的影响外，Ca在免疫功能和中间代谢方面的作用还解释了亚临床低钙血症对早期哺乳期观察到的几种疾病发展的贡献，并强调了其在高性能奶牛中的重要性。本综述旨在将最近的科学进展（例如关于乳腺在调节骨动员中的作用的发现）整合到Ca稳态的内分泌控制中。我们将讨论钙通过吸收，再吸收，分泌和动员的转运机制，以及通过甲状旁腺激素对钙的生理调节，[1] 除了饮食中需要的矿物质外，还需要25-二羟基维生素D，成纤维细胞生长因子23和血清素。为了改善低钙血症的预防策略，我们对维持正常血钙必要的生理机制及其内源性调节的认识应与来自畜群水平研究的数据相结合。利用这些研究，我们将讨论旨在减少亚临床低钙血症发生率的产前营养策略，以及产后补充钙的选择及其对早期泌尿健康和生产的影响。特别是对于可能干扰内源性适应过程的方法，例如补充维生素D代谢产物或大剂量的Ca，彻底了解可能引起不良的低血钙反弹效应的潜在机制，对于改善我们对过渡母牛的未来管理至关重要。研究人员需要继续努力，以了解钙稳态与​​预防策略之间的相互作用，对于优化奶牛健康和支持丰富的牛奶生产是必要的。