Tjardes K E, Buskirk D D, Allen M S, Ames N K, Bourquin L D, Rust S R
Department of Animal Science, Michigan State University, East Lansing 48824-1225, USA.
J Anim Sci. 2002 Mar;80(3):833-40. doi: 10.2527/2002.803833x.
Corn silage with high NDF concentration has the potential to reduce DMI because it has a greater filling effect in the rumen than low-NDF corn silage. Our objective was to determine whether ruminal fill influences DMI to the same extent with low- or high-NDF corn silage-based diets. Eight ruminally cannulated Holstein steers (198 +/- 13 kg) were randomly assigned to a 2 x 2 factorial arrangement of treatments in a replicated 4 x 4 Latin square design with 16-d periods. Treatments were diets containing corn silage from a normal hybrid (low-fiber; LF) or its male-sterile isogenic counterpart (high-fiber; HF), offered for ad libitum consumption to steers with or without rumen inert bulk (RIB). The LF and HF diets contained 33.8 and 50.8% dietary NDF, respectively. Rumen inert bulk was added at 25% of pretrial ruminal volume in the form of plastic-coated tennis balls filled with sand to achieve a specific gravity of 1.1 and a total volume of 7.5 L. No fiber level x inert bulk interactions were detected for DMI or NDF intake (P > 0.10), suggesting that DMI was limited to the same extent by physical fill at both levels of dietary fiber. Addition of RIB decreased DMI by an average of 10.7%, which was 65.5 g/L of added bulk. The HF diet depressed DMI by an average of 15.5%, increased NDF intake 27.1%, and reduced ruminal NDF turnover time by 21.0% compared to the LF diet (P < 0.01), with no effect on ruminal volume or amount of NDF in the rumen (P > 0.10). Addition of RIB also reduced ruminal NDF turnover time and amount of NDF in the rumen (11.8% and 20.7%, respectively; P < 0.01), with no change in ruminal digesta volume (P > 0.10). The HF treatment decreased digestibility of DM and GE (5.5 and 5.7%, respectively; P < 0.01) but increased NDF digestibility (10.4%; P < 0.01) compared to LF. Rumen inert bulk had no effect on digestibility of DM, NDF, or GE (P > 0.10). The lack of reduction in digesta volume with addition of inert fill suggests that DMI of light-weight steers receiving corn silage-based diets within a wide range of NDF concentrations was not regulated by ruminal distension alone.
中性洗涤纤维（NDF）浓度高的玉米青贮饲料有可能降低干物质采食量（DMI），因为它在瘤胃中的填充作用比低NDF玉米青贮饲料更强。我们的目标是确定在以低NDF或高NDF玉米青贮饲料为基础的日粮中，瘤胃充盈对DMI的影响程度是否相同。八头装有瘤胃瘘管的荷斯坦公牛（体重198±13千克）被随机分配到一个2×2析因处理组合中，采用重复的4×4拉丁方设计，每期16天。处理方式为给公牛提供含有正常杂交种玉米青贮饲料（低纤维；LF）或其雄性不育同基因对应物（高纤维；HF）的日粮，公牛自由采食，日粮中添加或不添加瘤胃惰性填充物（RIB）。LF和HF日粮的日粮NDF含量分别为33.8%和50.8%。以填充沙子的涂塑网球形式添加瘤胃惰性填充物，添加量为试验前瘤胃容积的25%，以达到比重1.1和总体积7.5升。在DMI或NDF摄入量方面未检测到纤维水平×惰性填充物的交互作用（P>0.10），这表明在两种膳食纤维水平下，DMI受物理填充的限制程度相同。添加RIB使DMI平均降低了10.7%，即每升添加填充物降低65.5克。与LF日粮相比，HF日粮使DMI平均降低了15.5%，使NDF摄入量增加了27.1%，并使瘤胃NDF周转时间缩短了21.0%（P<0.01），对瘤胃容积或瘤胃中NDF的量没有影响（P>0.10）。添加RIB还缩短了瘤胃NDF周转时间并减少了瘤胃中NDF的量（分别为11.8%和20.7%；P<0.01），瘤胃消化物容积没有变化（P>0.10）。与LF相比，HF处理降低了干物质（DM）和总能（GE）的消化率（分别降低5.5%和5.7%；P<0.01），但提高了NDF消化率（提高10.4%；P<0.01）。瘤胃惰性填充物对DM、NDF或GE的消化率没有影响（P>0.10）。添加惰性填充物后消化物容积没有减少，这表明在广泛的NDF浓度范围内，采食以玉米青贮饲料为基础日粮的轻体重公牛的DMI并非仅受瘤胃扩张调节。
