Symposium review: Transition cow calcium homeostasis—Health effects of hypocalcemia and strategies for prevention

摘要

The effects of subclinical hypocalcemia have beenexplored in numerous observational and mechanisticstudies in recent years. Besides obvious, well-knowneffects on muscle contractility, the role of Ca with respectto immune function and intermediary metabolismexplains the contribution of subclinical hypocalcemiato the development of several diseases observed inearly lactation and underlines its importance in highperformingdairy cows. The present review aims atintegrating recent scientific progress, such as discoveriesabout the role of the mammary gland in regulatingbone mobilization, into generally accepted aspectsof the endocrine control of Ca homeostasis. We willdiscuss Ca transport mechanisms through absorption,resorption, secretion, and mobilization, as well as thephysiological regulation of Ca through parathyroidhormone, 1,25-dihydroxyvitamin D, fibroblast growthfactor 23, and serotonin, in addition to dietary mineralrequirements. To improve hypocalcemia preventionstrategies, our knowledge of the physiological mechanismsnecessary to maintain normocalcemia and theirendogenous regulation should be combined with dataderived from herd-level studies. Using such studies, wewill discuss prepartum nutritional strategies aimed atreducing the incidence of subclinical hypocalcemia, aswell as options for postpartum Ca supplementation andtheir effects on early-lactation health and production.Especially in respect to approaches that might interferewith endogenous adaptation processes, such as supplementationwith vitamin D metabolites or large dosesof Ca, a thorough understanding of the underlyingmechanisms that might induce unwanted hypocalcemiarebound effects will be crucial to ameliorate our futuremanagement of transition cows. Continued efforts byresearchers to understand the interaction of Ca homeostasiswith prevention strategies is necessary to optimizecow health and support copious milk production.