The objective of this study was to assess the effect of oral calcium boluses at parturition on plasma total calcium (tCa), phosphorus (P), total magnesium (tMg), beta hydroxybutyrate (BHB) and milk yield during the postpartum (pp) of grazing Holstein cows. The study was conducted on a seasonal grazing dairy in Chile. Prepartum cows were fed an anionic diet (-86 mEq/kg DM). In 2019, 10 cows of parity 2, 3, and ≥ 4, respectively, were randomly assigned at parturition to a treatment group (n=30), receiving 2 boluses of oral Ca, (CaCl₂, providing 44 g Ca) 24 h apart, and matched by parity to a control group (n=30). A blood sample was obtained at d 1, 2, 3, 4 and 7 pp. Milk yield was recorded until 30 d pp. Minerals and milk yield were analysed by ANOVA for repeated measures. Treatment had no effect on tCa in parity 2 cows. However, in lactation 3, Ca supplementation increased the concentration of tCa at d 2 and 3 pp, and in lactation ≥ 4 boluses tended to increase tCa at d 2 pp. Higher BHB concentrations at d 4 pp were found in treated cows than in the control cows. Milk yield in lactation 2 was lower in the treated than the control group. In lactations ≥ 3, milk yield was higher in the treated than the control group. In conclusion, two oral Ca boluses at parturition 24 h apart in grazing cattle fed anionic prepartum diets, improved Ca status and milk yield during the postpartum period in cows ≥ 3 lactations.

这项研究的目的是评估分娩时口服钙大剂量对产后（pp）产后血浆总钙（tCa），磷（P），总镁（tMg），β羟基丁酸酯（BHB）和产奶量的影响。放牧荷斯坦奶牛。该研究是在智利的季节性放牧乳业上进行的。给产前母牛喂阴离子饮食（-86 mEq / kg DM）。在2019年，分娩时随机将10头均等2、3和≥4的母牛分入治疗组（n = 30），接受2次大剂量口服Ca（CaCl ₂，相距24小时提供44 g Ca），并通过奇偶校验匹配到对照组（n = 30）。在第1、2、3、4和7 pp采集血样。记录牛奶产量直至30 pp。通过ANOVA分析矿物质和牛奶产量以进行重复测量。治疗对同龄2头母牛的tCa没有影响。但是，在哺乳期3中，补钙会在d 2和3 pp时增加tCa的浓度，在哺乳期≥4次推注时，在d 2 pp时会增加tCa。在处理过的母牛中，在d 4 pp处发现的BHB浓度比在奶牛中高。控制奶牛。处理组的泌乳期2的产奶量低于对照组。在哺乳期≥3时，治疗组的产奶量高于对照组。总之，在分娩后以阴离子产前饮食喂养的放牧牛中，分娩时间隔24 h两次口服Ca丸剂，