Miles N, de Villiers J F, Dugmore T J
Cedara Research Station, Kwazulu-Natal Department of Agriculture, Pietermaritzburg, Republic of South Africa.
J S Afr Vet Assoc. 1995 Dec;66(4):206-12.
A 2-year study was conducted to determine the macromineral status of kikuyu grass pastures growing on representative soils in the KwaZulu-Natal Midlands. Herbage samples were collected at 25 to 35 day intervals during the growing season from 12 rotationally-grazed camps located on 3 sites. Seasonal mean herbage Ca and P concentrations were within the ranges 0.22 to 0.33% and 0.27 to 0.39%, respectively, while seasonal mean Ca:P ratios ranged from 1.1:1 to 0.63:1. Calcium concentrations and the Ca:P ratios were lowest in the midsummer months, while P concentrations increased in midsummer. In terms of the requirements of various classes of sheep and cattle, Ca concentrations and Ca:P ratios were frequently well below published critical limits. This finding, coupled with reports of kikuyu containing high levels of oxalate which reduce Ca absorption by ruminants, implies a major Ca insufficiency for animals pastured on kikuyu. Herbage Mg concentrations (seasonal mean range: 0.25 to 0.35%) were adequate in terms of the requirements of most classes of ruminants; however, K concentrations (seasonal mean range: 2.64 to 4.46%) were well in excess of animal requirements, and Mg absorption could be severely inhibited by the oversupply of K. In most camps the K:Ca+Mg ratio exceeded the reported safety threshold for grazing animals of 2.2, suggesting a high hypomagnesaemic tetany potential for animals on kikuyu pastures. Sodium concentrations in kikuyu were found to be largely inadequate in terms of animal requirements.
开展了一项为期两年的研究，以确定夸祖鲁 - 纳塔尔省中部代表性土壤上生长的狗尾草牧场的常量矿物质状况。在生长季节，每隔25至35天从位于3个地点的12个轮牧营地采集牧草样本。季节性牧草钙和磷浓度分别在0.22%至0.33%和0.27%至0.39%范围内，而季节性钙磷比在1.1:1至0.63:1之间。钙浓度和钙磷比在仲夏月份最低，而磷浓度在仲夏时增加。就各类绵羊和牛的需求而言，钙浓度和钙磷比经常远低于已公布的临界限值。这一发现，再加上关于狗尾草含有高浓度草酸盐从而降低反刍动物钙吸收的报道，意味着在狗尾草上放牧的动物存在严重的钙不足。就大多数反刍动物的需求而言，牧草镁浓度（季节性平均范围：0.25%至0.35%）充足；然而，钾浓度（季节性平均范围：2.64%至4.46%）远远超过动物需求，钾的过量供应可能会严重抑制镁的吸收。在大多数营地，钾与钙加镁的比例超过了报道的放牧动物安全阈值2.2，这表明狗尾草牧场上的动物发生低镁血症性搐搦的可能性很高。发现狗尾草中的钠浓度在动物需求方面大多不足。
