Van Vuuren A M, Krol-Kramer F, van der Lee R A, Corbijn H
Dienst Landbouwkundig Onderzoek, Instituut voor Veevoedingsonderzoek, Lelystad, The Netherlands.
J Dairy Sci. 1992 Aug;75(8):2215-25. doi: 10.3168/jds.S0022-0302(92)77982-X.
An experiment was carried out to study digestion and intestinal AA in three ruminally and duodenally cannulated, lactating cows fed freshly cut grass (Lolium perenne) fertilized with 500 and 275 kg of N/ha per yr, respectively. High N grass was fed in June and October, and low N grass was offered in July and September. Composite samples of the grass fed in each period also were tested for in situ degradation of OM, CP, and NDF. When low N grass was fed, the digestibilities of OM and CP were lower than when high N grass was fed. On low N grass, the duodenal N flow expressed per unit of N intake was higher, although the flow of AA N on low N grass was reduced in September, mainly because of reduced microbial protein synthesis from slower OM degradation of low N grass. Duodenal N flow per unit of N intake was related negatively to the N:OM ratio of the diet. The rate of N fertilization had no effect on ruminal OM and NDF turnover rates. Turnover and passage rates in this experiment were not different from reported data on cows on winter rations with similar DMI.
进行了一项实验，以研究三头瘤胃和十二指肠插管的泌乳奶牛对消化和肠道氨基酸的情况，这些奶牛分别饲喂每年每公顷施氮量为500千克和275千克的鲜切黑麦草（多年生黑麦草）。6月和10月饲喂高氮草，7月和9月提供低氮草。还对每个时期饲喂的草的混合样本进行了有机物质（OM）、粗蛋白（CP）和中性洗涤纤维（NDF）的原位降解测试。当饲喂低氮草时，OM和CP的消化率低于饲喂高氮草时。在低氮草上，每单位氮摄入量的十二指肠氮流量较高，尽管9月份低氮草上的氨基酸氮流量减少，主要是因为低氮草的OM降解较慢导致微生物蛋白合成减少。每单位氮摄入量的十二指肠氮流量与日粮的氮：OM比率呈负相关。氮肥施用量对瘤胃OM和NDF周转率没有影响。本实验中的周转率和通过率与报道的具有相似干物质摄入量（DMI）的冬季日粮奶牛的数据没有差异。
