Henson J E, Schingoethe D J, Maiga H A
Dairy Science Department, South Dakota State University, Brookings 57007-0647, USA.
J Dairy Sci. 1997 Feb;80(2):385-92. doi: 10.3168/jds.S0022-0302(97)75948-4.
Twelve lactating Holstein cows (9 multiparous and 3 primiparous) were used in a replicated 3 x 3 Latin square design with three periods of 4 wk each to evaluate diets containing three protein supplements that varied in ruminally undegradable protein and amino acid (AA) composition. Diets contained either 44% crude protein (CP) solvent-extracted soybean meal, expeller (mechanically extracted) soybean meal, or a blend of animal and vegetable proteins as the protein supplement. The animal and vegetable blend consisted of equal portions of protein from blood meal, corn gluten meal, meat and bone meal, and soybean meal. All diets contained 33.3% alfalfa haylage, 16.7% corn silage, and 50% of the respective concentrate mix (dry matter basis). Diets contained 17.4, 17.8, and 17.8% CP and 34, 45, and 45% of CP as ruminally undegradable protein, respectively. Dry matter intake, milk production and composition, and body weight were similar among treatments. Uptakes of AA by the mammary gland were similar among treatments. The apparent first-limiting AA for each diet was likely Met, but Lys and Phe were also potentially limiting. Varying degrees of protein degradability and AA composition within the range of this study did not affect lactational responses, indicating that all of these protein supplements were adequate to support milk production.
选用12头泌乳期荷斯坦奶牛（9头经产牛和3头初产牛），采用重复3×3拉丁方设计，每个阶段为期4周，以评估含有三种蛋白质补充料的日粮，这三种补充料的瘤胃不可降解蛋白和氨基酸（AA）组成有所不同。日粮中的蛋白质补充料分别为44%粗蛋白（CP）的溶剂浸提豆粕、压榨（机械浸提）豆粕或动植物蛋白混合物。动植物蛋白混合物由血粉、玉米蛋白粉、肉骨粉和豆粕中等量的蛋白质组成。所有日粮均含有33.3%的苜蓿青贮、16.7%的玉米青贮以及50%各自的精料混合料（干物质基础）。日粮的粗蛋白含量分别为17.4%、17.8%和17.8%，瘤胃不可降解蛋白分别占粗蛋白的34%、45%和45%。各处理间的干物质采食量、产奶量及乳成分和体重相似。各处理间乳腺对氨基酸的摄取量相似。每种日粮的表观第一限制性氨基酸可能是蛋氨酸，但赖氨酸和苯丙氨酸也可能具有限制性。在本研究范围内，不同程度的蛋白质降解率和氨基酸组成并未影响泌乳反应，这表明所有这些蛋白质补充料都足以支持产奶。
