Weigel D J, Elliott J P, Clark J H
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
J Dairy Sci. 1997 Jun;80(6):1150-9. doi: 10.3168/jds.S0022-0302(97)76042-9.
Five cows with ruminal cannulas were used in a 5 x 5 Latin square design to determine the effects of fat and amount and ruminal degradability of dietary crude protein (CP) on nutrient digestibility and production of milk and milk components. Treatments were 1) control; 2) 15% CP, soybean meal; 3) 15% CP, by-product proteins; 4) 18% CP, soybean meal; and 5) 18% CP, soybean meal and by-product proteins. Diets 2 through 5 contained 3.5% tallow. Diets consisted of 28% alfalfa haylage, 22% corn silage, and 50% concentrate on a dry matter (DM) basis. Fat did not affect dry matter intake or percentages and yields of fat and CP in milk but increased milk yield 2.5 kg/d. Fat did not affect N fractions in milk but decreased the percentages of short- and medium-chain fatty acids (C6:0 to C16:0) and increased the percentages of long-chain fatty acids (C18:0 and C18:1) in milk fat. Fat did not affect ruminal fermentation characteristics or the percentages of dietary DM, organic matter, CP, acid detergent fiber, neutral detergent fiber, starch, ether extract, and energy that were digested. An increase in dietary CP from 15 to 18% increased dry matter intake 1.7 kg/d; increased intake of gross energy 8 Mcal/d; increased the percentages and quantities of DM, organic matter, CP, and energy digested; increased the quantities of acid detergent fiber and neutral detergent fiber digested; decreased ruminal pH; increased concentrations of total volatile fatty acids; and increased NH3 N in ruminal fluid. However, the difference in dietary CP did not affect milk yield or composition. Replacement of soybean meal in the diet with a mixture of by-product proteins decreased NH3 N in ruminal fluid, tended to decrease concentrations of total volatile fatty acids and increase pH of ruminal fluid, but did not affect milk yield or percentages and yields of milk components.
选用5头装有瘤胃瘘管的奶牛，采用5×5拉丁方设计，以确定脂肪、日粮粗蛋白（CP）的含量及瘤胃降解率对养分消化率以及牛奶和乳成分产量的影响。处理方式如下：1）对照；2）15%CP，豆粕；3）15%CP，副产物蛋白；4）18%CP，豆粕；5）18%CP，豆粕和副产物蛋白。日粮2至5含有3.5%的牛脂。日粮按干物质（DM）基础计，由28%的苜蓿青贮、22%的玉米青贮和50%的精料组成。脂肪不影响干物质采食量、乳中脂肪和CP的百分比及产量，但使产奶量提高了2.5千克/天。脂肪不影响乳中的氮组分，但降低了乳脂肪中短链和中链脂肪酸（C6:0至C16:0）的百分比，增加了长链脂肪酸（C18:0和C18:1）的百分比。脂肪不影响瘤胃发酵特性，也不影响日粮干物质、有机物、CP、酸性洗涤纤维、中性洗涤纤维、淀粉、乙醚提取物和被消化能量的百分比。日粮CP从15%增加到18%，使干物质采食量增加1.7千克/天；使总能摄入量增加8兆卡/天；使被消化的干物质、有机物、CP和能量的百分比及数量增加；使被消化的酸性洗涤纤维和中性洗涤纤维数量增加；降低瘤胃pH值；增加总挥发性脂肪酸浓度；并增加瘤胃液中的氨氮。然而，日粮CP的差异不影响产奶量或乳成分。用副产物蛋白混合物替代日粮中的豆粕，可降低瘤胃液中的氨氮，使总挥发性脂肪酸浓度有降低趋势并提高瘤胃液pH值，但不影响产奶量或乳成分的百分比及产量。
