Department of Animal Sciences, University of Illinois, Urbana 61801.
Hamlet Protein A/S, Horsens, Denmark 8700.
J Dairy Sci. 2021 Mar;104(3):2979-2995. doi: 10.3168/jds.2020-18776. Epub 2021 Jan 15.
The aims of this experiment were (1) to compare the effects of a soybean meal with an enzymatic treatment (ESBM) to reduce the concentration of antinutritional factors versus a standard soybean meal (SBM) on foregut and small intestine digestion in weaned dairy calves and (2) to estimate the endogenous losses of crude protein (CP) in the small intestine. Our hypothesis was that a diet containing ESBM instead of SBM would improve ruminal and small intestine digestion and absorption of nutrients. A T-cannula was placed in the duodenum, and a second T-cannula was installed in the distal ileum of 12 Holstein calves at approximately 3 wk of age. Calves were weaned on d 42, and on d 50 they were assigned randomly to a quadruplicated 3 × 3 Latin square with 10-d periods. Digesta samples were collected on d 7 and 8 from the ileum and d 9 and 10 from the duodenum. The diets were fed for ad libitum intake and consisted of a calf starter (CS) of 20% CP with SBM as the main source of protein (CTRL), and an isonitrogenous CS with an ESBM instead of SBM (ENZT). A third diet with a low content of CP (10%) and no soy protein was fed to estimate endogenous N losses and digestibilities of test ingredients. Flows and digestibilities of nutrients were compared between CTRL and ENZT and their test ingredients (SBM vs. ESBM, respectively). Duodenal net flows of CP and total AA as well as ruminal microbial protein synthesis per kilogram of digested CP were greater, and flow of nonprotein N and CP true (corrected by endogenous and microbial flows) foregut digestibility were lower with ENZT than CTRL. The apparent small intestine digestibilities of CP and total AA were greater for ESBM than SBM, but there were no differences between the CTRL and ENZT diets. We observed no differences in digestibilities at the duodenum or ileum of starch or NDF, but true small intestine digestibilities of CP and all AA were greater with ENZT than CTRL. Total endogenous protein losses in the small intestine estimated from calves fed the low-CP with no soy protein diet were 37 ± 1.5 g of CP and 29 ± 1.4 g of AA/kg of DMI. These values may be considered the basal endogenous losses as they are similar to values obtained with the regression method, which estimates N losses when dietary N is null. Our results indicated that the inclusion of an ESBM improved the efficiency of ruminal microbial protein synthesis per digested kilogram of organic matter and CP, and increased CP and AA absorption in the small intestine despite a greater proportion of undigested dietary protein entering the duodenum.
（1）比较经酶处理的大豆粕（ESBM）降低抗营养因子浓度与标准大豆粕（SBM）对断奶奶牛前胃和小肠消化的影响，（2）估计小肠中粗蛋白（CP）的内源损失。我们的假设是，用含有 ESBM 的日粮代替 SBM 将改善瘤胃和小肠对养分的消化和吸收。在大约 3 周龄时，12 头荷斯坦犊牛的十二指肠中放置 T 型管，回肠中安装第二个 T 型管。犊牛在第 42 天断奶，第 50 天随机分配到一个 3×3 拉丁方的 4 个重复组，每个周期 10 天。在第 7 天和第 8 天从回肠收集消化物样本，第 9 天和第 10 天从十二指肠收集消化物样本。日粮自由采食，由 20%CP 的犊牛开食料组成，SBM 作为主要蛋白质来源（CTRL），用含有 ESBM 的等氮开食料代替 SBM（ENZT）。第三种低蛋白（10%）且不含大豆蛋白的日粮用于估计内源氮损失和试验成分的消化率。比较 CTRL 和 ENZT 及其试验成分（分别为 SBM 与 ESBM）之间的养分流量和消化率。与 CTRL 相比，ENZT 组 CP 和总氨基酸的十二指肠净流量以及每消化 CP 千克瘤胃微生物蛋白合成量更大，而非蛋白氮和 CP 真（校正内源和微生物流量）前胃消化率更低。ESBM 组 CP 和总氨基酸的小肠表观消化率大于 SBM 组，但 CTRL 和 ENZT 组之间没有差异。在十二指肠或回肠，淀粉或 NDF 的消化率没有差异，但 ENZT 组 CP 和所有氨基酸的小肠真消化率大于 CTRL 组。从喂饲低蛋白且不含大豆蛋白日粮的犊牛中估计的小肠总内源蛋白损失为 37±1.5 g CP 和 29±1.4 g AA/kg DMI。这些值可被视为基础内源损失，因为它们与回归法估计的当饲粮氮为零时的氮损失值相似。我们的结果表明，尽管进入十二指肠的未消化日粮蛋白比例更高，但添加 ESBM 提高了每消化千克有机物和 CP 的瘤胃微生物蛋白合成效率，并增加了小肠 CP 和氨基酸的吸收。
