Hussein H S, Berger L L
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
J Anim Sci. 1995 Dec;73(12):3503-9. doi: 10.2527/1995.73123503x.
The objective of this study was to determine the effects of source of dietary CP and level of ruminally protected lysine and methionine (RPLM) on feedlot performance and carcass characteristics of Holstein steers during a growing-finishing trial (266 d). A total of 168 Holstein steers (182.7 +/- 27.5 kg) were used in a completely randomized design experiment (eight treatments; three pens of seven steers/treatment). Steers were given ad libitum access to high-concentrate diets (13% CP) containing 71% whole shelled corn, 10% corn silage, 4% condensed distillers solubles, and 15% protein supplements (DM basis). Treatments were arranged as a 2 x 4 factorial. The main factors were two sources of dietary CP and four levels of RPLM. The sources of dietary CP were soybean meal (SBM) or SBM and urea (SBM-U). Urea-N replaced 50% of SBM-N in the SBM-U diet. The levels of RPLM were 0, 5, 10, and 15 g per steer daily. No interactions (P > .10) between source of dietary CP and level of RPLM were observed for feedlot performance or carcass characteristics. Feedlot performance showed an advantage (P < .10) to feeding SMB during the first 84 d of the trial and an advantage to feeding SBM-U during the last 98 d of the trial. However, feedlot performance for the whole trial and carcass characteristics (except for fat thickness) were not affected (P > .10) by the source of dietary CP. Steers fed diets containing SBM-U had 12% less (P < .10) fat thickness than those fed diets containing SBM. Supplementation of diets with increasing levels of RPLM did not affect (P > .10) ADG or carcass characteristics. However, DMI and gain:feed showed cubic (P < .10) responses to increasing dietary level of RPLM. Supplementation of RPLM at the 10 g/d level improved gain:feed by 12% during the last 98 d of the trial, and this was a direct response to the cubic effects of RPLM on DMI. Results suggest a cost advantage for replacing 50% of SBM-N with that from urea in high-corn diets without negative effects on feedlot performance or carcass characteristics of growing-finishing Holstein steers with extended feeding periods (266 d). These types of diets seem to meet the amino acid requirements and are not limiting in lysine and methionine.
本研究的目的是在一个育肥试验（266天）期间，确定日粮粗蛋白来源以及瘤胃保护性赖氨酸和蛋氨酸（RPLM）水平对荷斯坦公牛育肥性能和胴体特性的影响。总共168头荷斯坦公牛（体重182.7±27.5千克）用于一项完全随机设计实验（8种处理；每种处理7头公牛，分3个栏）。公牛可自由采食高能量日粮（粗蛋白含量13%），日粮包含71%的整粒脱壳玉米、10%的玉米青贮、4%的浓缩酒糟可溶物和15%的蛋白质补充料（干物质基础）。处理方式按2×4析因设计安排。主要因素为两种日粮粗蛋白来源和四个RPLM水平。日粮粗蛋白来源为豆粕（SBM）或豆粕与尿素（SBM-U）。在SBM-U日粮中，尿素氮替代了50%的豆粕氮。RPLM水平为每头公牛每天0、5、10和15克。对于育肥性能或胴体特性，未观察到日粮粗蛋白来源与RPLM水平之间存在交互作用（P>.10）。在试验的前84天，育肥性能显示饲喂SBM具有优势（P<.10），而在试验的最后98天，饲喂SBM-U具有优势。然而，整个试验期的育肥性能和胴体特性（除脂肪厚度外）不受日粮粗蛋白来源的影响（P>.10）。饲喂含SBM-U日粮的公牛脂肪厚度比饲喂含SBM日粮的公牛薄12%（P<.10）。随着RPLM添加水平的增加，日粮补充RPLM对平均日增重（ADG）或胴体特性没有影响（P>.10）。然而，干物质采食量（DMI）和增重:饲料比呈三次方响应（P<.10），随着日粮RPLM水平的增加而变化。在试验的最后98天，以10克/天的水平补充RPLM使增重:饲料比提高了12%，这是RPLM对DMI的三次方效应的直接反应。结果表明，在高玉米日粮中用尿素氮替代50%的豆粕氮具有成本优势，对育肥期延长（266天）的生长育肥荷斯坦公牛的育肥性能或胴体特性没有负面影响。这些类型的日粮似乎满足氨基酸需求，且在赖氨酸和蛋氨酸方面没有限制。
