Aldrich C G, Merchen N R, Parsons C M, Hussein H S, Ingram S, Clodfelter J R
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
J Anim Sci. 1997 Nov;75(11):3046-51. doi: 10.2527/1997.75113046x.
The objectives of these studies were to predict the effects of roasting and extrusion temperatures of whole soybeans (SB) on intestinal protein digestibility in cattle. Intestinal digestibility was assessed with a two-stage in vitro or in situ ruminal incubation/precision-fed cecectomized rooster bioassay. In Exp. 1, whole SB (raw SB or SB roasted to 141, 149, or 157 degrees C exit temperature from a commercial roaster and steeped for 30 min) were incubated in strained ruminal fluid and McDougall's buffer (50:50) at 39 degrees C for 16 h. In Exp. 2, SB (ground raw SB or SB extruded at 116, 138, or 160 degrees C) were placed in polyester bags (20 x 30 cm) and suspended in the ventral rumen of steers for 16 h. Lyophilized residue of the in vitro or in situ incubations and samples of raw SB and most extensively heated SB (roasted SB at 157 degrees C or extruded SB at 160 degrees C) for each respective experiment were crop-intubated to cecectomized roosters. Total excreta were collected for 48 h after intubation and lyophilized, and amino acid (AA) concentrations were determined. In Exp. 1, total AA digestibility was 61.6 and 84.5% for unincubated whole raw SB and 157 degrees C roasted SB, respectively, and 66.2, 88.9, 91.3, and 91.6% for in vitro residues of whole raw SB and SB roasted at 141, 149, and 157 degrees C, respectively. Trypsin inhibitor (TI) activity was 20.09, 1.69, 1.54, and 1.84 mg/g fat-free DM for unincubated whole raw SB and 141, 149, and 157 degrees C roasted SB, respectively, and 30.84, 1.01, .90, and .26 mg/g fat-free DM for in vitro residues of whole raw SB, 141, 149, and 157 degrees C roasted SB, respectively. In Exp. 2, total AA digestibility was 68.5 and 87.7% for unincubated ground raw SB and 160 degrees C extruded SB, respectively, and 81.9, 91.3, 89.7, and 89.4% for in situ residues of ground raw SB and 116, 138, and 160 degrees C extruded SB, respectively. Trypsin inhibitor activity was 17.61, 4.89, 4.08, and 1.56 mg/g fat-free DM for unincubated ground raw SB, 116, 138, and 160 degrees C extruded SB, respectively, and 3.62, .59, .55, and .21 mg/g fat-free DM for incubated ground raw SB, 116, 138, and 160 degrees C extruded SB, respectively. Heat treatment by roasting and extrusion improved AA digestibilities of SB, but there were no differences detected among the roasting or extrusion temperatures. Ruminal fermentation did not eliminate the negative effects of TI activity on intestinal digestibility of AA in whole SB but did reduce TI activity in ground SB.
这些研究的目的是预测全脂大豆（SB）的烘焙和挤压温度对牛肠道蛋白质消化率的影响。通过两阶段体外或原位瘤胃培养/精确饲喂切除盲肠公鸡生物测定法评估肠道消化率。在实验1中，将全脂SB（生全脂SB或用商业烘焙机烘焙至出料温度为141、149或157℃并浸泡30分钟的全脂SB）在39℃下于过滤后的瘤胃液和麦克道格尔缓冲液（50:50）中培养16小时。在实验2中，将全脂SB（磨碎的生全脂SB或在116、138或160℃下挤压的全脂SB）放入聚酯袋（20×30厘米）中，悬吊在阉牛的腹侧瘤胃中16小时。将每个实验的体外或原位培养的冻干残渣以及生全脂SB和加热程度最高的全脂SB（157℃烘焙的全脂SB或160℃挤压的全脂SB）样品经嗉囊插管法喂给切除盲肠的公鸡。插管后收集48小时的全部排泄物并冻干，然后测定氨基酸（AA）浓度。在实验1中，未培养的生全脂SB和157℃烘焙的全脂SB的总AA消化率分别为61.6%和84.5%，生全脂SB以及141、149和157℃烘焙的全脂SB的体外残渣的总AA消化率分别为66.2%、88.9%、91.3%和91.6%。未培养的生全脂SB和141、149和157℃烘焙的全脂SB的胰蛋白酶抑制剂（TI）活性分别为20.09、1.69、1.54和1.84毫克/克无脂干物质，生全脂SB以及141、149和157℃烘焙的全脂SB的体外残渣的TI活性分别为30.84、1.01、0.90和0.26毫克/克无脂干物质。在实验2中，未培养的磨碎生全脂SB和160℃挤压的全脂SB的总AA消化率分别为68.5%和87.7%，磨碎生全脂SB以及116、138和160℃挤压的全脂SB的原位残渣的总AA消化率分别为81.9%、91.3%、89.7%和89.4%。未培养的磨碎生全脂SB、116、138和160℃挤压的全脂SB的TI活性分别为17.61、4.89、4.08和1.56毫克/克无脂干物质，培养后的磨碎生全脂SB、116、138和160℃挤压的全脂SB的TI活性分别为3.62、0.59、0.55和0.21毫克/克无脂干物质。烘焙和挤压热处理提高了全脂大豆的氨基酸消化率，但在烘焙或挤压温度之间未检测到差异。瘤胃发酵并未消除TI活性对全脂大豆中氨基酸肠道消化率的负面影响，但确实降低了磨碎大豆中的TI活性。
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