Malestein A
Tijdschr Diergeneeskd. 1981 Jun 1;106(11):567-74.
Grass is high grade roughage. Its energy content (appr. 1650 kcal. NE of dry matter) approximates that of concentrates. As a rule, the protein content of dry matter is much higher than the minimum required for growth or milk production, and this may have an adverse effect on the utilization of Cu and Mg. The structural value of grass is another factor to bear in mind in feeding dairy cows, the more so when concentrates or other non- or less structural products are also fed. Of the mineral constituents the elements Ng, Na, Cu, Co and j require most attention. This is not the case when more than appr. 4 kg of concentrate daily are fed to cows. However, supplying Mg often continues to cause concern. The daily dry matter intake from grass is appr. 2.0-2.5 per cent of body weight, but this varies with the season, climate and indoor or outdoor feeding. Fully grazing cows can produce appr. 25 kg of milk in the spring and appr. 18 kg in the autumn. When the cows are kept indoors at night or kept at zero grazing, the production level is somewhat lower (see Table under 2.3). For cows showing a higher production concentrates are therefore required. To prevent too great an intake of intestinal parasites in young animals (calves), grazing aftermath is the most effective method, though it is not easy to carry out in every case. For stale or dry cows the feed intake from grass usually is too high. This may result in fat cows as well as an increased risk of milk fever.
青草是优质粗饲料。其能量含量（约每千克干物质含1650千卡净能）与精饲料相近。通常，干物质中的蛋白质含量远高于生长或产奶所需的最低量，这可能会对铜和镁的利用率产生不利影响。青草的结构性价值是饲喂奶牛时需要考虑的另一个因素，尤其是在同时饲喂精饲料或其他非结构性或低结构性产品时。在矿物质成分中，镁、钠、铜、钴和碘元素最需要关注。当每天给奶牛饲喂超过约4千克精饲料时，情况则并非如此。然而，镁的供应往往仍令人担忧。奶牛每天从青草中摄入的干物质约为体重的2.0% - 2.5%，但这会因季节、气候以及室内或室外饲养方式而有所不同。完全放牧的奶牛在春季大约能产奶25千克，秋季约产奶18千克。当奶牛夜间圈养或完全舍饲时，产奶水平会稍低一些（见表2.3）。因此，对于产奶量较高的奶牛，需要饲喂精饲料。为防止幼畜（犊牛）摄入过多肠道寄生虫，放牧再生草是最有效的方法，不过在每种情况下实施起来都不容易。对于待产或干奶期的奶牛，从青草中摄入的饲料量通常过高。这可能导致奶牛过肥，同时增加患产乳热的风险。
