Pregnant Holstein cows, 28 nulliparous and 51 parous, were blocked by parity and milk yield and randomly allocated to receive diets that differed in dietary cation-anion difference (DCAD), +130 or −130 mEq/kg, and supplemented with either calcidiol or cholecalciferol at 3 mg/11 kg of dry matter from 255 d of gestation until parturition. Blood was sampled thrice weekly prepartum, and on d 0, 1, 2, 3, 6, 9, 12, 15, 18, 21, 24, 27, and 30 postpartum to evaluate effects of the diets on vitamin D, mineral and bone metabolism, and acid-base status. Blood pH and concentrations of minerals, vitamin D metabolites, and bone-related hormones were determined, as were mineral concentrations and losses in urine and colostrum. Supplementing with calcidiol increased plasma concentrations of 25-hydroxyvitamin D₃, 3-epi 25-hydroxyvitamin D₃, 25-hydroxyvitamin D₂, 1,25-dihydroxyvitamin D₃, and 24,25-dihydroxyvitamin D₃ compared with supplementing with cholecalciferol. Cows fed the diet with negative DCAD had lesser concentrations of vitamin D metabolites before and after calving than cows fed the diet with positive DCAD, except for 25-hydroxyvitamin D₂. Feeding the diet with negative DCAD induced a compensated metabolic acidosis that attenuated the decline in blood ionized Ca (iCa) and serum total Ca (tCa) around calving, particularly in parous cows, whereas cows fed the diet with positive DCAD and supplemented with calcidiol had the greatest 1,25-dihydroxyvitamin D₃ concentrations and the lowest iCa and tCa concentrations on d 1 and 2 postpartum. The acidogenic diet or calcidiol markedly increased urinary losses of tCa and tMg, and feeding calcidiol tended to increase colostrum yield and increased losses of tCa and tMg in colostrum. Cows fed the diet with negative DCAD had increased concentrations of serotonin and C-terminal telopeptide of type 1 collagen prepartum compared with cows fed the diet with positive DCAD. Concentrations of undercarboxylated and carboxylated osteocalcin and those of adiponectin did not differ with treatment. These results provide evidence that dietary manipulations can induce metabolic adaptations that improve mineral homeostasis with the onset of lactation that might explain some of the improvements observed in health and production when cows are fed diets with negative DCAD or supplemented with calcidiol.

怀孕的荷斯坦奶牛，分别为28头和51头，受胎次和产奶量的限制，被随机分配以接受日粮中阳离子负离子差（DCAD）为+130或-130 mEq / kg的日粮，并补充了降钙素或从妊娠255 d至分娩前，胆干钙化固醇含量为3 mg / 11 kg干物质。在产前每周三次抽取血样，并在产后第0、1、2、3、6、9、12、15、18、21、24、27和30天取样，以评估饮食对维生素D，矿物质和骨骼的影响代谢和酸碱状态。测定血液的pH值以及矿物质，维生素D代谢物和与骨骼相关的激素的浓度，以及矿物质的浓度以及尿液和初乳中的损失。补充骨化二醇可增加血浆中25-羟基维生素D _3的浓度，3-EPI 25-羟基d ₃，25-羟基d ₂，1,25-二羟基维生素d ₃，和24,25-二羟基d ₃与胆钙化甾醇补充比较。饲喂DCAD阴性的日粮犊牛产犊前后维生素D代谢物的浓度低于饲喂DCAD阳性的日粮母牛，但25-羟基维生素D ₂除外。在日粮中饲喂负DCAD会引起代偿性代谢性酸中毒，从而减轻产犊前后血液中离子化Ca（iCa）和血清总Ca（tCa）的下降，特别是在同卵牛中，而日粮中饲喂DCAD阳性并补充了骨化二醇的母牛则表现出补偿性酸中毒。最大的1,25-二羟基维生素D ₃产后第1天和第2天的iCa和tCa浓度最低，而iCa和tCa最低。产酸饮食或骨化二醇显着增加了tCa和tMg的尿流失，而饲喂骨化二醇倾向于增加初乳的产量，并增加初乳中tCa和tMg的流失。与饲喂DCAD阳性的奶牛相比，饲喂DCAD阴性的奶牛血清5-羟色胺和1型胶原蛋白产前C末端端肽的浓度增加。羧化和羧化不足的骨钙素的浓度与脂联素的浓度随处理而无差异。