Andrighetto I, Bailoni L, Cozzi G, Tolosa H F, Hartman B, Hinds M, Sapienza D
Department of Animal Science, University of Padova, Italy.
J Dairy Sci. 1993 Sep;76(9):2624-31. doi: 10.3168/jds.S0022-0302(93)77598-0.
The rate and extent of degradation of forage feed fractions contained in alfalfa and Italian ryegrass hays were determined. Nylon bags filled with 4 g of each forage were suspended in the rumen of two cannulated cows immediately before feeding and incubated for 10 different times (0, 2, 4, 8, 12, 24, 48, 72, 120, and 168 h). The alfalfa hay, which had lower NDF, showed a lower extent, but a higher rate, of NDF degradation than the Italian ryegrass (41.1 vs. 59.8% and 4.64 vs. 2.91%/h, respectively). Alfalfa cell walls were degraded more rapidly than Italian ryegrass even though their lignin content was higher. The hemicellulose fermentation of alfalfa showed a longer lag time (13 h) and an undegradable fraction nearly twice that for Italian ryegrass (63.3 vs. 37.1%). Cellulose from alfalfa was degraded at a higher rate than NDF or ADF, indicating that cellulose may be the primary site of hydrolysis of the cell wall in the rumen. Calculations based on in situ degradability indicate that alfalfa can have a higher inclusion than Italian ryegrass in diets for dairy cows because of lower NDF and greater availability of cell contents.
测定了紫花苜蓿和意大利黑麦草干草中饲料组分的降解率和降解程度。在每次喂食前，将装有4克每种草料的尼龙袋悬挂在两头装有瘤胃瘘管的奶牛瘤胃中，并在10个不同时间点（0、2、4、8、12、24、48、72、120和168小时）进行培养。中性洗涤纤维（NDF）含量较低的紫花苜蓿干草，其NDF降解程度较低，但降解速率较高，分别为41.1%和59.8%，降解速率分别为4.64%/小时和2.91%/小时。尽管紫花苜蓿细胞壁的木质素含量较高，但其降解速度比意大利黑麦草更快。紫花苜蓿的半纤维素发酵滞后期较长（13小时），不可降解部分几乎是意大利黑麦草的两倍（63.3%对37.1%）。紫花苜蓿中的纤维素降解速率高于NDF或酸性洗涤纤维（ADF），这表明纤维素可能是瘤胃中细胞壁水解的主要部位。基于原位降解性的计算表明，由于紫花苜蓿的NDF含量较低且细胞内容物的可利用性较高，因此在奶牛日粮中的添加量可能高于意大利黑麦草。
