Department of Animal Sciences, University of Florida, Gainesville 32611; DH Barron Reproductive and Perinatal Biology Research Program, University of Florida, Gainesville 32611.
Department of Animal Sciences, University of Florida, Gainesville 32611.
J Dairy Sci. 2021 Jan;104(1):683-701. doi: 10.3168/jds.2020-18448. Epub 2020 Nov 6.
Objectives were to determine the effects of an injectable formulation of calcitriol on Ca concentration, risk of clinical diseases, and performance in dairy cows. Cows were blocked by lactation number (1 vs. >1) and calving sequence and, within block, assigned randomly within 6 h of calving to receive subcutaneously vehicle only (CON, n = 450) or 200 (CAL200, n = 450) or 300 μg of 1α,25-dihydroxyvitamin D (CAL300, n = 450). Cows were fed the same acidogenic diet prepartum. Blood was sampled before treatment administration and again during the first 11 d postpartum and analyzed for concentrations of ionized Ca (iCa), total Ca (tCa), Mg (tMg), and P (tP), β-hydroxybutyrate, carboxylated osteocalcin (cOC), and undercarboxylated osteocalcin (uOC). Cows were evaluated for diseases in the first 60 d postpartum. Reproduction and survival were monitored for the first 300 d postpartum. Calcitriol increased concentration of blood iCa (CON = 1.12 vs. CAL200 = 1.23 vs. CAL300 = 1.27 mM), plasma tCa (CON = 2.29 vs. CAL200 = 2.44 vs. CAL300 = 2.46 mM), and plasma tP (CON = 1.72 vs. CAL200 = 2.21 vs. CAL300 = 2.28 mM), and differences were observed during the first 5 d postpartum for iCa and tCa, and the first 7 d postpartum for tP. Concentrations of tMg were lower in calcitriol-treated cows than in CON cows (CON = 0.81 vs. CAL200 = 0.78 vs. CAL300 = 0.75 mM), and differences were observed during the first 5 d postpartum. Calcitriol increased plasma concentrations of cOC (CON = 14.5 vs. CAL200 = 23.0 vs. CAL300 = 19.8 ng/mL) and uOC (CON = 1.6 vs. CAL200 = 3.4 vs. CAL300 = 2.6 ng/mL). Prevalence of subclinical hypocalcemia was less in calcitriol-treated cows (CON = 19.0 vs. CAL200 = 4.7 vs. CAL300 = 9.3%); however, benefits on health were only observed in overconditioned cows (n = 270/1,350). Calcitriol reduced incidence of retained placenta (CON = 14.3 vs. CAL200 = 5.1 vs. CAL300 = 5.9%), puerperal metritis (CON = 12.7 vs. CAL200 = 6.1 vs. CAL300 = 2.5%), and morbidity (CON = 72.1 vs. CAL200 = 57.4 vs. CAL300 = 56.9%) in cows with BCS greater than 3.50, but no benefit on health was observed in cows with BCS equal to or less than 3.50 at parturition. Milk yield did not differ among treatments. Pregnancy at first AI did not differ, but pregnancy rate after the first AI was slower for calcitriol-treated cows because of reduced insemination rate and pregnancy per AI. We found that CAL200 reduced death but increased culling in cows without calving problems. Collectively, results indicate that treatment with calcitriol at parturition was effective in improving concentrations of iCa, tCa, and tP, which reduced the risk of hypocalcemia. Pregnancy rate was reduced by calcitriol treatment, and benefits on health performance were limited to overconditioned cows. Thus, treatment of all cows is not supported, and proper identification of cohorts of cows that benefit from postpartum interventions that increase blood calcitriol or calcium is needed.
目的是确定注射用钙三醇制剂对奶牛血钙浓度、临床疾病风险和生产性能的影响。奶牛按泌乳次数（1 次与>1 次）和产犊顺序分组，在产后 6 h 内，随机分为皮下注射仅给予载体（CON，n=450）或 200（CAL200，n=450）或 300 μg 1α，25-二羟维生素 D（CAL300，n=450）。奶牛在产前给予相同的产酸日粮。在治疗前采血，产后第 1 天再次采血，分析离子钙（iCa）、总钙（tCa）、镁（tMg）和磷（tP）、β-羟丁酸、羧化骨钙素（cOC）和未羧化骨钙素（uOC）浓度。产后 60 d 内评估奶牛疾病。产后 300 d 内监测繁殖和存活情况。钙三醇增加血液 iCa 浓度（CON=1.12 与 CAL200=1.23 与 CAL300=1.27 mM）、血浆 tCa（CON=2.29 与 CAL200=2.44 与 CAL300=2.46 mM）和血浆 tP（CON=1.72 与 CAL200=2.21 与 CAL300=2.28 mM），产后第 15 天 iCa 和 tCa 差异明显，第 17 天 tP 差异明显。与 CON 奶牛相比，钙三醇治疗奶牛的 tMg 浓度较低（CON=0.81 与 CAL200=0.78 与 CAL300=0.75 mM），产后第 1~5 天差异明显。钙三醇增加血浆 cOC（CON=14.5 与 CAL200=23.0 与 CAL300=19.8 ng/mL）和 uOC（CON=1.6 与 CAL200=3.4 与 CAL300=2.6 ng/mL）浓度。钙三醇治疗奶牛亚临床低钙血症的患病率较低（CON=19.0 与 CAL200=4.7 与 CAL300=9.3%）；然而，健康益处仅见于超重奶牛（n=270/1350）。钙三醇降低了产后胎盘滞留（CON=14.3 与 CAL200=5.1 与 CAL300=5.9%）、子宫炎（CON=12.7 与 CAL200=6.1 与 CAL300=2.5%）和发病率（CON=72.1 与 CAL200=57.4 与 CAL300=56.9%），但在产犊时体况评分等于或低于 3.50 的奶牛中，健康状况没有改善。处理之间的牛奶产量没有差异。首次人工授精的妊娠率没有差异，但由于授精率和每人工授精妊娠率降低，钙三醇治疗奶牛的首次人工授精妊娠率较慢。我们发现 CAL200 降低了死亡率，但增加了无产犊问题奶牛的淘汰率。总的来说，结果表明，在分娩时给予钙三醇治疗可有效提高 iCa、tCa 和 tP 浓度，从而降低低钙血症的风险。钙三醇治疗降低了妊娠率，对健康性能的益处仅限于超重奶牛。因此，不支持对所有奶牛进行治疗，需要正确识别受益于增加血液钙三醇或钙的产后干预措施的奶牛群体。
