Broderick G A, Koegel R G, Walgenbach R P, Kraus T J
Agricultural Research Service, USDA US Dairy Forage Research Center, Madison 53706, USA.
J Dairy Sci. 2002 Jul;85(7):1894-901. doi: 10.3168/jds.S0022-0302(02)74264-1.
Renewed interest exists in using grass forages to dilute the higher crude protein (CP) and lower digestible fiber present in legumes fed to lactating dairy cows. A 3 x 3 Latin square feeding study with 4-wk periods was conducted with 24 Holstein cows to compare ryegrass silage, either untreated control or macerated (intensively conditioned) before ensiling, with alfalfa silage as the sole dietary forage. Ryegrass silages averaged [dry matter (DM) basis] 18.4% CP, 50% neutral detergent fiber (NDF), and 10% indigestible acid detergent fiber (ADF) (control) and 16.6% CP, 51% NDF, and 12% indigestible ADF (macerated). Alfalfa silage was higher in CP (21.6%) and lower in NDF (44%) but higher in indigestible ADF (26%). A lower proportion of the total N in macerated ryegrass silage was present as nonprotein N than in control ryegrass and alfalfa silages. Diets were formulated to contain 41% DM from either rye-grass silage, or 51% DM from alfalfa silage, plus high moisture corn, and protein concentrates. Diets averaged 17.5% CP and 28 to 29% NDF. The shortfall in CP on ryegrass was made up by feeding 7.6% more soybean meal. Intake and milk yields were similar on control and macerated ryegrass; however, DM intake was 8.3 kg/d greater on the alfalfa diet. Moreover, feeding the alfalfa diet increased BW gain (0.48 kg/d) and yield of milk (6.1 kg/d), FCM (6.8 kg/d), fat (0.26 kg/d), protein (0.25 kg/d), lactose (0.35 kg/d), and SNF (0.65 kg/d) versus the mean of the two ryegrass diets. Both DM efficiency (milk/DM intake) and N efficiency (milk-N/N-intake) were 27% greater, and apparent digestibility was 16% greater for DM and 53% greater for NDF and ADF, on the ryegrass diets. However, apparent digestibility of digestible ADF was greater on alfalfa (96%) than on ryegrass (average = 91%). Also, dietary energy content (estimated as net energy of lactation required for maintenance, milk yield, and weight gain) per unit of digested DM was similar for all three diets. Results of this trial indicated that, relative to ryegrass silage, feeding alfalfa silage stimulated much greater feed intake, which supported greater milk production.
人们重新对使用禾本科牧草来稀释泌乳奶牛所采食豆科牧草中较高的粗蛋白（CP）含量和较低的可消化纤维产生了兴趣。用24头荷斯坦奶牛进行了一项为期4周的3×3拉丁方饲养研究，以比较黑麦草青贮料（未处理的对照或青贮前进行揉碎处理）与苜蓿青贮料作为唯一日粮粗饲料的效果。黑麦草青贮料平均（以干物质（DM）计）含CP 18.4%、中性洗涤纤维（NDF）50%、酸性洗涤纤维（ADF）中不可消化部分10%（对照），以及CP 16.6%、NDF 51%、酸性洗涤纤维中不可消化部分12%（揉碎处理）。苜蓿青贮料的CP含量较高（21.6%），NDF含量较低（44%），但酸性洗涤纤维中不可消化部分含量较高（26%）。与对照黑麦草青贮料和苜蓿青贮料相比，揉碎处理的黑麦草青贮料中总氮以非蛋白氮形式存在的比例较低。日粮配方设计为要么含41% DM的黑麦草青贮料，要么含51% DM的苜蓿青贮料，再加上高水分玉米和蛋白质浓缩料。日粮平均含CP 17.5%和NDF 28%至29%。黑麦草日粮中CP不足部分通过多饲喂7.6%的豆粕来弥补。对照黑麦草和揉碎处理的黑麦草组的采食量和产奶量相似；然而，苜蓿日粮组的干物质采食量每天多8.3千克。此外，与两种黑麦草日粮的平均值相比，饲喂苜蓿日粮使体重增加（每天0.48千克）以及牛奶产量（每天6.1千克）、乳脂校正乳（每天6.8千克）、脂肪（每天0.26千克）、蛋白质（每天0.25千克）、乳糖（每天0.35千克）和非脂固形物（每天0.65千克）均有所增加。两种黑麦草日粮的干物质效率（牛奶/干物质采食量）和氮效率（牛奶氮/氮摄入量）均高出27%，且干物质表观消化率高出16%，NDF和ADF的表观消化率高出53%。然而，酸性洗涤纤维可消化部分的表观消化率在苜蓿日粮组（96%）高于黑麦草日粮组（平均为91%）。而且，三种日粮每单位消化干物质的日粮能量含量（以维持、产奶量和体重增加所需的泌乳净能估算）相似。该试验结果表明，相对于黑麦草青贮料，饲喂苜蓿青贮料能刺激采食量大幅增加，从而支持更高的产奶量。
