Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
J Dairy Sci. 2018 Feb;101(2):1365-1378. doi: 10.3168/jds.2017-13376. Epub 2017 Nov 23.
Calcium homeostatic mechanisms are challenged in periparturient multiparous dairy cattle due to the rapid transport of large amounts of calcium into the mammary gland associated with colostrogenesis, resulting in decreased plasma total calcium concentration ([Ca]). An unresolved issue is the timing of the decrease in plasma [Ca] relative to the time of parturition, with the consensus view being that plasma [Ca] does not decrease until after parturition. The objective of this study, therefore, was to characterize the change in plasma [Ca] over time in periparturient dairy cattle. Plasma and mid-stream urine samples were collected daily starting 3 d before calving from 104 periparturient Holstein-Friesian dairy cows in a herd fed an acidogenic total mixed ration during the late dry period. Mixed-models ANOVA and linear and multivariable regression analyses were conducted. Plasma [Ca] decreased in periparturient multiparous cattle (n = 70) but not in primiparous cattle (n = 34). Compared with mean values approximately 72 h before parturition ([Ca] = 2.32 mmol/L), mean plasma [Ca] in multiparous cattle first decreased at 9 h before parturition (2.13 mmol/L) and remained decreased for up to 48 h after parturition, with the lowest mean value (1.87 mmol/L) occurring at 28 h after parturition. Mean 24-h urine Ca excretion was calculated to decrease by 3.5 to 3.8 g in periparturient multiparous cattle. Regression analysis indicated that plasma [Ca] in the 12-h period before and 24-h period after parturition was strongly and negatively associated with age but was also negatively associated with milk production indices. We conclude that plasma [Ca] was decreased at least 9 h before parturition in multiparous dairy cattle fed an acidogenic diet in late gestation, and that calcium homeostasis was disrupted for 2 to 3 d around parturition.
钙稳态机制在围产期多胎奶牛中受到挑战，因为大量钙快速转运到与初乳生成有关的乳腺，导致血浆总钙浓度([Ca])下降。一个未解决的问题是血浆[Ca]相对于分娩时间的下降时间，共识观点是，血浆[Ca]直到分娩后才下降。因此，本研究的目的是描述围产期奶牛血浆[Ca]随时间的变化。在一个饲养在干后期采用酸化全混合日粮的牛群中，从 104 头围产期荷斯坦-弗里森奶牛中采集血浆和中流尿液样本，从分娩前 3 天开始每天采集一次。进行了混合模型方差分析和线性及多变量回归分析。围产期多胎奶牛(n = 70)的血浆[Ca]下降，但初产奶牛(n = 34)的血浆[Ca]没有下降。与分娩前约 72 小时的平均值( [Ca] = 2.32 mmol/L)相比，多胎奶牛的平均血浆[Ca]在分娩前 9 小时首次下降(2.13 mmol/L)，并在分娩后长达 48 小时内持续下降，最低平均值(1.87 mmol/L)出现在分娩后 28 小时。计算得出，围产期多胎奶牛的 24 小时尿液钙排泄量减少了 3.5 至 3.8 g。回归分析表明，分娩前 12 小时和分娩后 24 小时的血浆[Ca]与年龄呈强烈负相关，但也与产奶量指数呈负相关。我们得出结论，在妊娠晚期饲喂酸化日粮的多胎奶牛中，血浆[Ca]至少在分娩前 9 小时下降，并且在分娩前后约 2 至 3 天钙稳态受到破坏。
