免疫激活引起的低钙血症是哺乳动物物种间的共同反应。但在其他物种中，由于增加发病率和死亡率的风险，不建议补充钙。产后早期的奶牛在急性炎症后血中钙浓度会下降，因此常规在转换期给予补钙治疗，特别是对于遭受急性疾病的奶牛。然而，我们不知道在急性免疫激活期间，钙的补充治疗对炎症反应的影响。我们的目标是比较接受自发钙静脉输注(IVCa)和未接受自发钙静脉输注(对照组)的产后奶牛在静注脂多糖(LPS)的挑战下的临床、炎症和代谢反应。14头奶牛进行匹配对照随机对照设计，通过静脉注射LPS(0.040或0.045μg/kg体重)进行挑战，其中7头接受IVCa，7头接受0.9% NaCl注射。同时，牛的离子钙浓度(iCa)进行监测，并在12小时内持续自动调节使其保持正常的钙平衡。我们在挑战开始后24小时内对奶牛进行监测，并收集了血液样本以测量葡萄糖、β-羟基丁酸、非酯化脂肪酸、尿素氮、细胞因子、急性期蛋白和皮质醇的浓度的变化。实验结果表明，钙补充治疗并不影响早产期奶牛的炎症反应，但可能会改变急性全身炎症的临床反应。

Hypocalcemia induced by immune activation is a conserved response across mammalian species; however, administration of Ca is discouraged in other species as it is associated with increased morbidity and mortality. Early postpartum cows experience a decrease in circulating Ca concentration following acute inflammation. Corrective Ca therapy during the transition period, particularly in dairy cows experiencing acute disease, is common practice. However, the effect of Ca administration on the inflammatory response during acute immune activation is unknown. Our objective was to compare the clinical, inflammatory, and metabolic response to an intravenous (IV) lipopolysaccharide (LPS) challenge between postpartum cows infused, or not, with IV Ca to maintain eucalcemia. Cows (n = 14, 8 ± 1 d in milk) were enrolled in a matched-pair randomized controlled design to receive IV Ca (IVCa) or sterile 0.9% NaCl (CTRL) during an IV LPS challenge (0.040 or 0.045 µg of LPS/kg of body weight over 1 h). Ionized Ca (iCa) was monitored cow-side, and IV Ca infusion was adjusted in a eucalcemic clamp for 12 h following the start of LPS infusion. Cows were monitored during the 24 h following challenge and serial blood samples were collected to quantify concentrations of glucose, β-hydroxybutyrate, nonesterified fatty acids, urea nitrogen, cytokines, acute-phase proteins, and cortisol. Blood iCa concentration decreased to 0.87 ± 0.03 mM in CTRL during challenge, and by design, iCa concentration was maintained within 3% of baseline in IVCa. Body temperature, heart rate, and respiratory rate were monitored for 24 h following the start of challenge and did not differ between groups. A treatment × time interaction was identified such that serum cortisol concentrations increased in both groups at 2 h but decreased to a greater extent at 6 h in IVCa compared with CTRL. Rumination time (min/h) over the first 12 h following challenge was greater in IVCa, but total rumination time in the 24 h following challenge did not differ from CTRL. Serum glucose and nonesterified fatty acid concentrations decreased, and β-hydroxybutyrate and urea nitrogen concentrations increased over time, but did not differ between groups. Acute leukopenia occurred in both groups at 4 h before leukocytosis was observed at 24 h with total white blood cell counts returning to baseline within 72 h. Plasma concentrations of tumor necrosis factor (TNF) and interleukin-10 (IL-10) increased within 1 h following the start of challenge and did not differ between groups. Serum haptoglobin and serum amyloid A concentrations increased within the 24 h following challenge and were elevated through 72 h but did not differ between groups. Eucalcemia during the acute systemic inflammatory response did not alter the TNF or IL-10 cytokine response, or the acute-phase protein SAA and haptoglobin response in this LPS challenge model; however, eucalcemia was associated with a more rapid decline in cortisol response and greater rumination time in the first 12 h following challenge. We did not find evidence that eucalcemia exacerbated the inflammatory response in early postpartum cows, but Ca administration may alter the clinical response to acute systemic inflammation.The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).