Calsamiglia S, Hongerholt D D, Crooker B A, Stern M D, Hartnell G F, Hintz R L
Department of Animal Science, University of Minnesota, St. Paul 55108.
J Dairy Sci. 1992 Sep;75(9):2454-62. doi: 10.3168/jds.S0022-0302(92)78007-2.
Forty-eight multiparous cows were blocked by calving date and milk production and assigned randomly to a TMR formulated to contain 68 or 55% of dietary CP as ruminally degradable CP. Diets contained corn silage, alfalfa haylage, and ground corn. Supplemental CP was soybean meal for the control diet or a combination of soybean meal, expeller-processed soybean meal, and fish meal for the low degradable protein diet. Two 10-wk phases began on d 31 +/- 3 (phase 1) and 110 +/- 7 postpartum [phase 2, all cows received subcutaneous implantations of pelleted (400 mg) bST (sometribove) every 14 d]. Dietary energy, CP, ruminally degradable CP, NDF, and ADF were similar between dietary treatments. Production of FCM increased in response to bST but was not affected by dietary treatment. Cows fed the expeller-processed soybean meal and fish meal TMR produced milk that contained less milk fat in phase 1 and less milk protein content in both phases. The DMI, BW, and body condition scores were not affected by diet. Hematocrit, plasma urea N, albumin, total protein, creatinine, glucose, and serum insulin were similar between dietary treatments. Replacing soybean meal with expeller processed soybean meal and fish meal did not affect ruminal degradation of protein or milk production but decreased milk fat and protein contents.
48头经产奶牛按产犊日期和产奶量进行分组，并随机分配到两种全混合日粮（TMR）中，其中一种日粮的瘤胃可降解粗蛋白（CP）含量为日粮CP的68%，另一种为55%。日粮包含玉米青贮、苜蓿干草青贮和粉碎玉米。对照组日粮的补充CP为豆粕，低降解蛋白日粮的补充CP为豆粕、压榨豆粕和鱼粉的混合物。两个10周阶段分别在产后31±3天（阶段1）和110±7天开始（阶段2，所有奶牛每14天接受一次皮下植入400mg的颗粒状bST（重组牛生长激素））。两种日粮处理之间的日粮能量、CP、瘤胃可降解CP、中性洗涤纤维（NDF）和酸性洗涤纤维（ADF）相似。校正乳产量因bST而增加，但不受日粮处理的影响。饲喂压榨豆粕和鱼粉TMR的奶牛在阶段1产的牛奶中乳脂含量较低，在两个阶段中产的牛奶中乳蛋白含量均较低。干物质采食量（DMI）、体重（BW）和体况评分不受日粮影响。两种日粮处理之间的血细胞比容、血浆尿素氮、白蛋白、总蛋白、肌酐、葡萄糖和血清胰岛素相似。用压榨豆粕和鱼粉替代豆粕不影响蛋白质的瘤胃降解或产奶量，但会降低乳脂和乳蛋白含量。
