Willms C L, Berger L L, Merchen N R, Fahey G C, Fernando R L
Dept. of Anim. Sci., University of Illinois, Urbana 61801.
J Anim Sci. 1991 Dec;69(12):4939-50. doi: 10.2527/1991.69124939x.
The effects of increasing dietary CP level on N retention (Exp. 1) and intestinal supply of amino acids (AA; Exp. 2) were studied in lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw (AHPWS). Soybean meal (SBM) was substituted for corn to increase CP level in both experiments. In Exp. 1, an incomplete design for the two-way elimination of error was used to allot 24 ram lambs (mean BW = 25 kg) within breed to six CP levels (6, 8, 10, 12, 14, and 16% of DM). Neutral detergent fiber digestibility and N retention increased quadratically (P = .06 and P less than .01, respectively) with increasing CP level. Nitrogen retention, expressed as a percentage of N intake, was greatest for lambs fed 12% CP (20.7%) but was greatest for lambs fed 14% CP when expressed as grams per day (4.0 g/d). In Exp. 2, five multicannulated St. Croix lambs (34 kg) were used in a 5 x 5 Latin square design. Treatments were 8.5, 11, 13.5, 16, and 18.5% dietary CP. Chromic oxide was used as a digesta flow marker and purines were used as a bacterial marker. Protein level had no effect on extent of dietary CP degradation in the rumen (69 +/- 3.2%). True ruminal OM digestibility increased (P less than .01) linearly and ruminal fluid NH3 N concentration increased (P less than .01) quadratically with increasing CP level. Total, bacterial, and nonbacterial N and AA flows to the duodenum increased (P less than .05) linearly with increasing CP level. Duodenal AA profile (g/100 g total AA) was altered slightly. The essential AA valine, isoleucine, phenylalanine, lysine, and arginine increased (P less than .05) and methionine decreased (P less than .05) in proportion to other AA with increasing CP level. Flows of all essential AA increased with increasing CP level. Apparent small intestinal N and AA disappearance increased linearly (P less than .05) and apparent total tract N digestibility increased (P less than .01) quadratically with increasing CP level. These data are interpreted to indicate that maximal N retention and fiber digestibility in diets based on AHPWS are obtained at 12% CP, even though the intestinal supply of AA continues to increase with increasing CP level. Supplementation of diets based on AHPWS with an extensively degraded protein source (SBM) does not substantially alter the profile of AA entering the duodenum compared to the AA profile of bacterial protein.
在以碱性过氧化氢处理麦秸（AHPWS）为基础日粮的羔羊中，研究了提高日粮粗蛋白（CP）水平对氮保留（实验1）和肠道氨基酸（AA）供应（实验2）的影响。在两个实验中，均用豆粕（SBM）替代玉米以提高CP水平。在实验1中，采用不完全双因素误差消除设计，将24只品种内的公羔羊（平均体重=25千克）分配到6个CP水平（占干物质的6%、8%、10%、12%、14%和16%）。随着CP水平的提高，中性洗涤纤维消化率和氮保留呈二次曲线增加（分别为P = 0.06和P＜0.01）。以氮摄入量的百分比表示时，饲喂12%CP的羔羊氮保留最高（20.7%），但以每天克数表示时，饲喂14%CP的羔羊氮保留最高（4.0克/天）。在实验2中，5只多瘘管的圣克罗伊羔羊（34千克）采用5×5拉丁方设计。处理为日粮CP水平8.5%、11%、13.5%、16%和18.5%。氧化铬用作食糜流动标记物，嘌呤用作细菌标记物。蛋白质水平对瘤胃中日粮CP降解程度无影响（69±3.2%）。随着CP水平的提高，真胃瘤胃有机物消化率呈线性增加（P＜0.01），瘤胃液氨氮浓度呈二次曲线增加（P＜0.01）。随着CP水平的提高，进入十二指肠的总氮量、细菌氮量和非细菌氮量以及氨基酸流量呈线性增加（P＜0.05）。十二指肠氨基酸谱（克/100克总氨基酸）略有改变。随着CP水平的提高，必需氨基酸缬氨酸、异亮氨酸、苯丙氨酸、赖氨酸和精氨酸增加（P＜0.05），蛋氨酸与其他氨基酸成比例减少（P＜0.05）。所有必需氨基酸的流量均随CP水平的提高而增加。随着CP水平的提高，小肠表观氮和氨基酸消失量呈线性增加（P＜0.05），全消化道表观氮消化率呈二次曲线增加（P＜0.01）。这些数据表明，即使随着CP水平的提高肠道氨基酸供应持续增加，但以AHPWS为基础的日粮中，在CP水平为12%时可获得最大氮保留和纤维消化率。与细菌蛋白的氨基酸谱相比，用大量降解蛋白源（SBM）补充以AHPWS为基础的日粮，并不会显著改变进入十二指肠的氨基酸谱。
