Min B R, Attwood G T, Reilly K, Sun W, Peters J S, Barry T N, McNabb W C
Nutrition and Behavior Group, AgResearch, Grasslands Research Centre, Private Bag 11008, Palmerston North, New Zealand.
Can J Microbiol. 2002 Oct;48(10):911-21. doi: 10.1139/w02-087.
Condensed tannins in forage legumes improve the nutrition of sheep by reducing ruminal degradation of plant protein and increasing crude protein flow to the intestine. However, the effects of condensed tannins in forage legumes on rumen bacterial populations in vivo are poorly understood. The aim of this study was to investigate the specific effects of condensed tannins from Lotus corniculatus on four proteolytic rumen bacteria in sheep during and after transition from a ryegrass (Lolium perenne)-white clover (Trifolium repens) diet (i.e., low condensed tannins) to a Lotus corniculatus diet (i.e., higher condensed tannins). The bacterial populations were quantified using a competitive polymerase chain reaction. Lotus corniculatus was fed with or without ruminal infusions of polyethylene glycol (PEG), which binds to and inactivates condensed tannins, enabling the effect of condensed tannins on bacterial populations to be examined. When sheep fed on ryegrass-white clover, populations of Clostridium proteoclasticum B316T, Butyrivibrio fibrisolvens C211a, Eubacterium sp. C12b, and Streptococcus bovis B315 were 1.5 x 10(8), 1.1 x 10(6), 4.6 x 10(8), and 7.1 x 10(6) mL(-1), respectively. When the diet was changed to Lotus corniculatus, the average populations (after 8-120 h) of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis decreased (P < 0.001) to 2.4 x 10(7), 1.1 x 10(5), 1.1 x 10(8), and 2.5 x 10(5) mL(-1), respectively. When PEG was infused into the rumen of sheep fed Lotus corniculatus, the populations of C. proteoclasticum, B. fibrisolvens, Eubacterium sp., and S. bovis were higher (P < 0.01-0.001) than in sheep fed Lotus corniculatus without the PEG infusion, with average populations (after 8-120 h) of 4.9 x 10(7), 3.8 x 10(5), 1.9 x 10(8), and 1.0 x 10(6), respectively. Sheep fed the Lotus corniculatus diet had lower rumen proteinase activity, ammonia, and soluble nitrogen (P < 0.05-0.001) than sheep that were fed Lotus corniculatus plus PEG. The Lotus corniculatus diet reduced rumen nitrogen digestibility (P < 0.05) and ammonia pool size and increased the flow of undegraded feed nitrogen to the abomasum. The nitrogen intake, rumen non-ammonia nitrogen pool size, rumen microbial non-ammonia nitrogen pool size, and abomasal microbial non-ammonia nitrogen fluxes were similar both in sheep fed only Lotus corniculatus and in sheep fed Lotus corniculatus plus PEG, but nonmicrobial non-ammonia nitrogen flux to the abomasum was higher (P < 0.01) for the sheep fed only Lotus corniculatus. Although condensed tannins in Lotus corniculatus reduced the populations of some proteolytic bacteria, total ruminal microbial protein and microbial protein outflow to the abomasum were unchanged, suggesting a species-specific effect of condensed tannins on bacteria in the rumen.
豆科牧草中的缩合单宁通过减少植物蛋白在瘤胃中的降解并增加粗蛋白向肠道的流动，从而改善绵羊的营养状况。然而，人们对豆科牧草中的缩合单宁对体内瘤胃细菌种群的影响了解甚少。本研究的目的是调查在从黑麦草（多年生黑麦草）-白三叶（白车轴草）日粮（即低缩合单宁）过渡到百脉根日粮（即高缩合单宁）期间及之后，百脉根中的缩合单宁对绵羊体内四种蛋白水解瘤胃细菌的具体影响。使用竞争性聚合酶链反应对细菌种群进行定量。给绵羊饲喂百脉根时，添加或不添加瘤胃灌注聚乙二醇（PEG），PEG可与缩合单宁结合并使其失活，从而能够研究缩合单宁对细菌种群的影响。当绵羊饲喂黑麦草-白三叶时，解蛋白梭菌B316T、溶纤维丁酸弧菌C211a、真杆菌属C12b和牛链球菌B315的种群数量分别为1.5×10⁸、1.1×10⁶、4.6×10⁸和7.1×10⁶ mL⁻¹。当日粮改为百脉根时，解蛋白梭菌、溶纤维丁酸弧菌、真杆菌属和牛链球菌的平均种群数量（8 - 120小时后）下降（P < 0.001），分别降至2.4×10⁷、1.1×10⁵、1.1×10⁸和2.5×10⁵ mL⁻¹。当向饲喂百脉根的绵羊瘤胃中灌注PEG时，解蛋白梭菌、溶纤维丁酸弧菌、真杆菌属和牛链球菌的种群数量高于（P < 0.01 - 0.001）未灌注PEG的饲喂百脉根的绵羊，平均种群数量（8 - 120小时后）分别为4.9×10⁷、3.8×10⁵、1.9×10⁸和1.0×10⁶。饲喂百脉根日粮的绵羊瘤胃蛋白酶活性、氨和可溶性氮含量低于（P < 0.05 - 0.001）饲喂百脉根加PEG的绵羊。百脉根日粮降低了瘤胃氮消化率（P < 0.05）和氨池大小，并增加了未降解饲料氮向皱胃的流动。仅饲喂百脉根的绵羊和饲喂百脉根加PEG的绵羊的氮摄入量、瘤胃非氨氮池大小、瘤胃微生物非氨氮池大小以及皱胃微生物非氨氮通量相似，但仅饲喂百脉根的绵羊向皱胃的非微生物非氨氮通量更高（P < 0.01）。尽管百脉根中的缩合单宁减少了一些蛋白水解细菌的种群数量，但瘤胃总微生物蛋白和向皱胃流出的微生物蛋白没有变化，这表明缩合单宁对瘤胃细菌具有物种特异性影响。
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