Hristov A N, McAllister T A, Cheng K J
Research Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
J Anim Sci. 1998 Dec;76(12):3146-56. doi: 10.2527/1998.76123146x.
The effect of site of supplementation of a mixture of two crude preparations (Enzyme C and Enzyme X) of exogenous polysaccharide-degrading enzymes (EPDE) was studied in vivo using four ruminally and duodenally cannulated heifers (Exp. 1). The treatments were as follows: control (no EPDE), EPDE supplied through the diet (EF, 47.0 g/d), and EPDE infused continuously into the abomasum (EA, 41.6 g/d). Enzyme treatment increased the concentration of soluble reducing sugars (P < .05) and decreased NDF content (P < .05) in the treated feed, but this did not increase the rate or extent of in sacco disappearance of DM from the feed. Compared with control, ruminal fermentation was not affected by EF, but abomasal infusion increased (P < .05) rumen ammonia levels and shifted ruminal VFA patterns. Ruminal carboxymethylcellulase (CMCase) and xylanase activities were not affected by treatment. Abomasal infusion increased (P < .05) duodenal xylanase activity as compared with control and EF, but apparent digestion of DM, NDF, and CP were not affected by treatment. Negligible levels of CMCase and amylase reached the duodenum. During an in vitro experiment (Exp. 2), abomasal stability of the two EPDE was studied over a range of pH from 3.39 to .85, with or without pepsin. Carboxymethylcellulase activity (in Enzymes C and X) and beta-glucanase activity (in Enzyme C) were largely unstable against pepsin proteolysis (P < .001) and low pH (P < .001). Xylanase and amylase activities were resistant to pepsin but irreversibly inactivated at low pH. These two experiments showed that abomasal supplementation of EPDE did not successfully supply cellulases and amylases to the intestine, due partially to their limited resistance to low pH and pepsin proteolysis. Although EPDE significantly increased the level of xylanase activity at the duodenum, this did not significantly improve total tract digestion.
利用四头安装了瘤胃和十二指肠瘘管的小母牛，在体内研究了两种外源多糖降解酶（EPDE）粗制品（酶C和酶X）混合物的添加部位的影响（实验1）。处理方式如下：对照（不添加EPDE）、通过日粮供应EPDE（EF，47.0克/天）以及持续向皱胃注入EPDE（EA，41.6克/天）。酶处理增加了处理后饲料中可溶性还原糖的浓度（P <.05）并降低了中性洗涤纤维含量（P <.05），但这并未提高饲料中干物质的瘤胃袋消失率或消失程度。与对照相比，EF对瘤胃发酵没有影响，但皱胃注入增加了（P <.05）瘤胃氨水平并改变了瘤胃挥发性脂肪酸模式。瘤胃羧甲基纤维素酶（CMCase）和木聚糖酶活性不受处理影响。与对照和EF相比，皱胃注入增加了（P <.05）十二指肠木聚糖酶活性，但干物质、中性洗涤纤维和粗蛋白的表观消化率不受处理影响。到达十二指肠的CMCase和淀粉酶水平可忽略不计。在一项体外实验（实验2）中，研究了在pH值从3.39到0.85的范围内，有或没有胃蛋白酶时两种EPDE的皱胃稳定性。羧甲基纤维素酶活性（在酶C和X中）和β-葡聚糖酶活性（在酶C中）对胃蛋白酶水解（P <.001）和低pH（P <.001）基本不稳定。木聚糖酶和淀粉酶活性对胃蛋白酶有抗性，但在低pH下不可逆地失活。这两项实验表明，向皱胃补充EPDE未能成功地向肠道提供纤维素酶和淀粉酶，部分原因是它们对低pH和胃蛋白酶水解的抗性有限。尽管EPDE显著提高了十二指肠木聚糖酶活性水平，但这并未显著改善全消化道消化率。
