Goff J P, Reinhardt T A, Horst R L
USDA, Agricultural Research Service, National Animal Disease Center, Ames, IA 50010-0070, USA.
J Dairy Sci. 1995 Nov;78(11):2388-94. doi: 10.3168/jds.S0022-0302(95)76867-9.
Milk fever is the clinical disease associated with severe hypocalcemia in dairy cows. In this experiment, we tested the hypothesis that calcium homeostasis is a result of a decreased concentration of receptors for 1,25-dihydroxyvitamin D in the tissues of cows that develop milk fever. Samples of colon mucosa were obtained for analysis of vitamin D receptor concentration in a longitudinal study of Jersey cows during the 2 wk before and after parturition. In the first study, 21 cows fed an alfalfa hay diet were biopsied every 3rd d from 2 wk before to 2 wk after calving. The concentration of vitamin D receptor in the colon during late gestation was three- to fourfold higher than the concentration of vitamin D receptor in the colon mucosa in nonpregnant cows (90 +/- 8 vs. 26 +/- 5 fmol/mg of protein). At parturition, colon concentration of vitamin D receptor decreased to 66 +/- 7.5 fmol/mg of protein. During early lactation, concentrations of vitamin D receptor in the colon were similar to precalving concentrations. There was no significant difference of concentrations of vitamin D receptor in the colon prior to calving, at calving, or in early lactation between cows that did develop milk fever and those that did not. Results were similar in a second study, in which 7 cows were fed a high cation alfalfa diet, and 6 cows were fed the same diet with anionic salts added. Those data do not support the hypothesis that decreased concentrations of vitamin D receptor prior to calving is a causative factor of milk fever within the Jersey breed. However, a decline of concentrations of vitamin D receptor in tissue at calving may reduce the ability of all cows to respond to the calcium demands of lactation.
乳热症是与奶牛严重低钙血症相关的临床疾病。在本实验中，我们检验了这样一个假设：钙稳态是由于患乳热症奶牛组织中1,25 - 二羟基维生素D受体浓度降低所致。在一项对泽西奶牛分娩前后2周的纵向研究中，采集结肠黏膜样本以分析维生素D受体浓度。在第一项研究中，21头以苜蓿干草为食的奶牛在产犊前2周开始至产犊后2周，每隔3天进行一次活检。妊娠后期结肠中维生素D受体的浓度比未怀孕奶牛结肠黏膜中维生素D受体的浓度高3至4倍（分别为90±8与26±5 fmol/mg蛋白质）。分娩时，结肠中维生素D受体浓度降至66±7.5 fmol/mg蛋白质。在泌乳早期，结肠中维生素D受体的浓度与产犊前浓度相似。患乳热症的奶牛和未患乳热症的奶牛在产犊前、产犊时或泌乳早期结肠中维生素D受体浓度没有显著差异。第二项研究结果相似，该研究中7头奶牛喂食高阳离子苜蓿日粮，6头奶牛喂食添加了阴离子盐的相同日粮。这些数据不支持这样的假设：产犊前维生素D受体浓度降低是泽西品种奶牛乳热症的致病因素。然而，产犊时组织中维生素D受体浓度的下降可能会降低所有奶牛对泌乳期钙需求的反应能力。
