Boucher S E, Calsamiglia S, Parsons C M, Stein H H, Stern M D, Erickson P S, Utterback P L, Schwab C G
Department of Biological Sciences, University of New Hampshire, Durham, New Hampshire 03824, USA.
J Dairy Sci. 2009 Sep;92(9):4489-98. doi: 10.3168/jds.2008-1884.
The objectives of this experiment were to measure intestinal digestibility of AA in rumen undegradable protein (RUP-AA) in soybean meal (SBM) and expeller SBM (SoyPlus, West Central, Ralston, IA; SP) and to determine if these feeds contain a constant protein fraction that is undegradable in the rumen and indigestible in the small intestine, as assumed in the French Institut National de la Recherche Agronomique (Paris, France) and Scandinavian AAT-PBV (AAT = AA absorbed from small intestine; PBV = protein balance in the rumen) models. Three samples of SBM and 3 samples of SP were obtained from the Feed Analysis Consortium Inc. (Savoy, IL). To obtain the RUP fraction, samples were ruminally incubated in situ for 16 h in 4 lactating cows, and the collected rumen undegraded residues (RUR) were pooled by sample. Subsamples of the intact feeds and RUR were crop intubated to 4 cecectomized roosters, and total excreta were collected for 48 h. Intact feeds, RUR, and excreta were analyzed for AA. Basal endogenous AA loss estimates were obtained from fasted birds and were used to calculate standardized digestibility of AA in the intact feeds and RUP-AA. Indigestibility coefficients of the intact feeds were calculated as (100 - % standardized AA digestibility), and indigestibility of the RUR was calculated as [(100 - % ruminal degradation of AA) x [(100 - % standardized RUP-AA digestibility)]/100]. Results indicated that standardized digestibility of feed-AA was similar to standardized digestibility of RUP-AA for SBM and SP samples and that standardized digestibility of individual AA differed within samples. Standardized feed-AA and RUP-AA digestibility values were lowest for Lys and Cys and highest for Trp and Met. Results also indicated that SBM and SP did not contain a constant protein fraction that was both undegradable in the rumen and indigestible in the small intestine. Indigestibility values of RUR were lower than in intact feeds, suggesting that SBM and SP contain a protein fraction that is indigestible in the intestine but partly degradable in the rumen, digestible in the intestine after ruminal incubation, or both.
本试验的目的是测定豆粕（SBM）和压榨豆粕（SoyPlus，美国中西部合作公司，罗尔斯顿，爱荷华州；SP）中瘤胃不可降解蛋白（RUP - AA）的氨基酸肠道消化率，并确定这些饲料是否含有如法国国家农业研究院（法国巴黎）和斯堪的纳维亚AAT - PBV（AAT = 从小肠吸收的氨基酸；PBV = 瘤胃中的蛋白质平衡）模型所假设的在瘤胃中不可降解且在小肠中不可消化的恒定蛋白质部分。从饲料分析联盟公司（伊利诺伊州萨沃伊）获取了3份SBM样品和3份SP样品。为获得RUP部分，将样品在4头泌乳奶牛的瘤胃中进行原位培养16小时，收集的瘤胃未降解残渣（RUR）按样品合并。将完整饲料和RUR的子样本经嗉囊插管投喂给4只切除盲肠的公鸡，并收集48小时的总排泄物。对完整饲料、RUR和排泄物进行氨基酸分析。基础内源氨基酸损失估计值来自禁食的鸡，并用于计算完整饲料和RUP - AA中氨基酸的标准消化率。完整饲料的不可消化系数计算为（100 - 氨基酸标准消化率%），RUR的不可消化率计算为[（100 - 氨基酸瘤胃降解率%）×（100 - RUP - AA标准消化率%）]/100。结果表明，SBM和SP样品的饲料氨基酸标准消化率与RUP - AA的标准消化率相似，且各样品中单个氨基酸的标准消化率有所不同。赖氨酸和半胱氨酸的饲料氨基酸和RUP - AA标准消化率值最低，色氨酸和蛋氨酸最高。结果还表明，SBM和SP不含有在瘤胃中不可降解且在小肠中不可消化的恒定蛋白质部分。RUR的不可消化率值低于完整饲料，这表明SBM和SP含有在肠道中不可消化但在瘤胃中部分可降解、瘤胃培养后在肠道中可消化或两者兼有的蛋白质部分。
