Thilsing-Hansen T, Jørgensen R J, Enemark J M D, Larsen T
The Royal Veterinary and Agricultural University, Department of Clinical Studies, Frederiksberg, Denmark.
J Dairy Sci. 2002 Jul;85(7):1855-62. doi: 10.3168/jds.S0022-0302(02)74259-8.
One potential way of preventing parturient hypocalcemia in the dairy cow is to feed dry cow rations very low in calcium (<20 g/d); but, because it is difficult to formulate rations sufficiently low in calcium, this principle has been almost abandoned. Recent studies have shown, however, that it is possible to prevent milk fever, as well as subclinical hypocalcemia, by supplementing the dry cow ration with sodium aluminium silicate (zeolite A), which has the capacity to bind calcium. The aim of this study was to further evaluate the effect, if any, of such supplementation on other blood constituents, feed intake, and milk production in the subsequent lactation. A total of 31 pregnant dry cows about to enter their third or later lactation were assigned as experimental or control cows according to parity and expected date of calving. The experimental cows received 1.4 kg of zeolite pellets per d (0.7 kg of pure zeolite A) for the last 2 wk of pregnancy. Blood samples were drawn from all cows 1 wk before the expected date of calving, at calving, at d 1 and 2 after calving, and 1 wk after calving. Additionally, a urine sample was drawn 1 wk before the expected date of calving. Zeolite supplementation significantly increased the plasma calcium level on the day of calving, whereas plasma magnesium as well as inorganic phosphate was suppressed. Serum 1,25(OH)2D was significantly increased 1 wk before the expected date of calving among the experimental cows, whereas there was no difference in the urinary excretion of the bone metabolite deoxypyridinoline between the two groups. Feed intake was decreased among the zeolite-treated cows during the last 2 wk of pregnancy. No effect was observed on milk yield, milk fat, and milk protein in the subsequent lactation. The mechanisms and interactions involved in zeolite supplementation are discussed in relation to the observed improvement in parturient calcium homeostasis and to the observed depression in blood magnesium and inorganic phosphate.
预防奶牛产褥期低钙血症的一种潜在方法是给干奶牛饲喂钙含量极低（<20克/天）的日粮；但是，由于很难配制出钙含量足够低的日粮，这一原则几乎已被摒弃。然而，最近的研究表明，通过在干奶牛日粮中添加硅铝酸钠（A型沸石）来预防产乳热以及亚临床低钙血症是可行的，因为硅铝酸钠有结合钙的能力。本研究的目的是进一步评估这种添加物对后续泌乳期其他血液成分、采食量和产奶量的影响（若有）。根据胎次和预计产犊日期，将总共31头即将进入第三胎或更高胎次泌乳期的怀孕干奶牛分为试验组和对照组。试验组奶牛在怀孕的最后2周每天饲喂1.4千克沸石颗粒（相当于0.7千克纯A型沸石）。在预计产犊日期前1周、产犊时、产犊后第1天和第2天以及产犊后1周，采集所有奶牛的血样。此外，在预计产犊日期前一周采集尿样。添加沸石显著提高了产犊当天的血浆钙水平，而血浆镁和无机磷水平受到抑制。在试验组奶牛中，预计产犊日期前1周血清1,25(OH)2D显著升高，而两组之间骨代谢物脱氧吡啶啉尿排泄量没有差异。在怀孕的最后2周，经沸石处理的奶牛采食量下降。在后续泌乳期，未观察到对产奶量、乳脂和乳蛋白有影响。结合观察到的产犊时钙稳态的改善以及血液镁和无机磷的降低，讨论了添加沸石所涉及的机制和相互作用。
