Verdaris J N, Evans J L
J Dairy Sci. 1976 Jul;59(7):1271-7. doi: 10.3168/jds.S0022-0302(76)84355-X.
Sixteen dry Holstein cows were assigned four groups combining either .2 or 2.1% calcium and pH of either 4.5 or 6.1 in a 2 X 2 factorial arrangement of treatments to study the effect of diet calcium and acidity (pH) on voluntary intake of dry matter, mineral metabolism, and blood constituents. The 86-day experiment was started 84 days prepartum and completed 2 days postpartum. Voluntary dry matter ingestion tended to be higher with higher calcium and acidity (lower pH) diets. Calcium nutriture was improved by more acid diets. More total calcium was apparently absorbed (26 and 7 g) when the diet contained 2.1% calcium, but the .2% calcium diet resulted in a higher apparent percent absorption (25 and 17%) during the dry period. An increased apparent absorption (70 and 5 g) and utilization of diet calcium occurred with the higher calcium treatment at 2 days postpartum. Magnesium and phosphorus utilizations were improved with lower diet calcium. Although experimental treatments had no significant effect on blood minerals, serum calcium decreased 12% 2 days postpartum. A better calcium nutriture was provided by the higher calcium diets when the diets maintained a positive balance for magnesium and phosphorus.
16头干奶期荷斯坦奶牛被分为四组，采用2×2析因设计，分别给予钙含量为0.2%或2.1%、pH值为4.5或6.1的日粮，以研究日粮钙和酸度（pH值）对干物质采食量、矿物质代谢及血液成分的影响。86天的试验在产前84天开始，产后2天结束。钙含量较高且酸度较高（pH值较低）的日粮，其干物质采食量有增加趋势。酸度较高的日粮可改善钙营养状况。日粮钙含量为2.1%时，总钙表观吸收量明显较高（分别为26克和7克），但在干奶期，钙含量为0.2%的日粮表观吸收率较高（分别为25%和17%）。产后2天，较高钙处理组的日粮钙表观吸收量（分别为70克和5克）及利用率增加。日粮钙含量较低时，镁和磷的利用率提高。虽然试验处理对血液矿物质无显著影响，但产后2天血清钙下降了12%。当日粮对镁和磷保持正平衡时，较高钙日粮能提供更好的钙营养。
