Roffler R E, Schwab C G, Satter L D
J Dairy Sci. 1976 Jan;59(1):80-4. doi: 10.3168/jds.S0022-0302(76)84158-6.
In three trials, we studied the effect of incremental amounts of intraruminally infused urea on mean ruminal ammonia concentration of steer fed at 2-h intervals. Basal rations contained these percentages of crude protein and total digestible nutrients (dry matter basis); Trial I, 11.1 and 81; Trial II, 6.0 and 54; Trial III, 6.5 and 58. Mean ruminal ammonia concentration reached 5 mg ammonia nitrogen/100 ml rumen fluid at crude protein equivalents of 12.0, 9.3, and 9.4% in I, II, and III. Once ruminal ammonia began to accumulate, there was a linear relationship between intake of urea and mean concentration of amino acids of plasma, serving as an indirect measure of amino acid absorption from the intestine, was not increased by increased intake of urea in III. Results of this experiment support the concept from in vitro data that microbial protein synthesis is unaffected by ruminal ammonia concentration in excess of 5 mg ammonia nitrogen/100 ml rumen fluid.
在三项试验中，我们研究了瘤胃内逐步增加尿素输注量对每隔2小时饲喂一次的阉牛瘤胃平均氨浓度的影响。基础日粮含有以下百分比的粗蛋白和总可消化养分（干物质基础）：试验I，11.1%和81%；试验II，6.0%和54%；试验III，6.5%和58%。在试验I、II和III中，当粗蛋白当量分别达到12.0%、9.3%和9.4%时，瘤胃平均氨浓度达到5毫克氨氮/100毫升瘤胃液。一旦瘤胃氨开始积累，尿素摄入量与血浆氨基酸平均浓度之间存在线性关系，血浆氨基酸平均浓度可间接衡量氨基酸从肠道的吸收情况，在试验III中，尿素摄入量增加并未使其升高。本实验结果支持体外数据得出的概念，即瘤胃氨浓度超过5毫克氨氮/100毫升瘤胃液时，微生物蛋白质合成不受影响。
