Liesegang A, Chiappi C, Risteli J, Kessler J, Hess H D
Institute of Animal Nutrition, University of Zurich, Zurich, Switzerland.
J Anim Physiol Anim Nutr (Berl). 2007 Apr;91(3-4):120-9. doi: 10.1111/j.1439-0396.2006.00651.x.
At the initiation of lactation, Ca homeostatic mechanisms have to react to a tremendous increase in demand for Ca. Mobilization of Ca from bone and increased absorption from the gastrointestinal tract are required to re-establish homeostasis. It has been shown that dietary anions play an important role in the prevention of milk fever by mobilizing Ca from bone and by increasing Ca absorption in the GI tract. The purpose of the present study was to investigate the influence of different Ca contents in diets supplemented with anionic salts on bone metabolism of dairy cows. Twenty-four holstein cows (housed inside, second to fourth lactation) without a milk fever history were divided into four groups (A, B, C, D). Each group was fed a different diet which was given from day 263 of gestation till the day of parturition. Group A and B received a low calcium diet (4 g/kg DM) whereas group C and D received a high Ca diet (8 g/kg DM). In addition group B and D received anionic salts. The DCAD was calculated with the formula: DCAD (mEq/kg DM)=(0.2 Ca2++0.16 Mg2++Na++K+)-(Cl-+0.6 S2-+0.65 P3-). Blood and urine samples were collected on days 256, 270 and 277 of gestation, on the day of parturition as well as the following 5 days and on days 9, 14 and 19 after parturition. Serum Ca, P, Mg, ICTP, OC, VITD, PTH and urinary pH were analysed. The bone resorption marker ICTP showed a significant increase after parturition in all the groups. On the contrary, the bone formation marker OC decreased after parturition in all the groups. The VITD concentrations in group D and the urinary pH in group B were significantly lower compared to the other groups (p<0.05). The Ca concentrations tended to be higher in group B around parturition than in all the other groups. No significant influence of the four different diets on all the other parameters could be shown. In conclusion, this data showed that the addition of anions and the different Ca contents had no significant influence on bone resorption and bone formation markers. This may be because of the fact that the dietary cation-anion balance was not low enough (DCAD-group A: 181 mEq/kg DM, group B: -48 mEq/kg DM, group C: 210 mEq/kg DM and group D: 28 mEq/kg DM) to induce a metabolic acidosis with all its positive effects on calcium metabolism.
在泌乳开始时，钙稳态机制必须对钙需求的大幅增加做出反应。需要从骨骼中动员钙并增加胃肠道对钙的吸收，以重新建立体内平衡。研究表明，日粮阴离子通过从骨骼中动员钙和增加胃肠道对钙的吸收，在预防产乳热方面发挥重要作用。本研究的目的是调查添加阴离子盐的日粮中不同钙含量对奶牛骨骼代谢的影响。将24头无产乳热病史的荷斯坦奶牛（圈养，第二至第四胎次）分为四组（A、B、C、D）。每组从妊娠第263天至分娩日饲喂不同的日粮。A组和B组饲喂低钙日粮（4 g/kg干物质），而C组和D组饲喂高钙日粮（8 g/kg干物质）。此外，B组和D组添加阴离子盐。用以下公式计算DCAD：DCAD（mEq/kg干物质）=（ (0.2Ca^{2 + } + 0.16Mg^{2 + } + Na^ + + K^ +) ）-（ (Cl^ - + 0.6S^{2 - } + 0.65P^{3 - }) ）。在妊娠第256、270和277天、分娩日及其后的5天以及分娩后第9、14和19天采集血液和尿液样本。分析血清钙、磷、镁、骨钙素（ICTP）、骨钙蛋白（OC）、维生素D（VITD）、甲状旁腺激素（PTH）和尿液pH值。所有组分娩后骨吸收标志物ICTP均显著升高。相反，所有组分娩后骨形成标志物OC均下降。与其他组相比，D组的维生素D浓度和B组的尿液pH值显著降低（p<0.05）。B组分娩前后的钙浓度往往高于其他所有组。未显示四种不同日粮对所有其他参数有显著影响。总之，这些数据表明，添加阴离子和不同的钙含量对骨吸收和骨形成标志物没有显著影响。这可能是因为日粮阳离子-阴离子平衡不够低（DCAD-A组：181 mEq/kg干物质，B组：-48 mEq/kg干物质，C组：210 mEq/kg干物质，D组：28 mEq/kg干物质），无法诱导代谢性酸中毒及其对钙代谢的所有积极影响。
