McAllister T A, Bae H D, Jones G A, Cheng K J
Agriculture Canada, Research Station, Lethbridge, Alberta.
J Anim Sci. 1994 Nov;72(11):3004-18. doi: 10.2527/1994.72113004x.
Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta. Most feeds contain a surface layer that is resistant to attachment and therefore to digestion. Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process. Proliferation of primary colonizing cells produces glycocalyx-enclosed microcolonies. Secondary colonizers from the ruminal fluid associate with microcolonies, resulting in the formation of multispecies microbial biofilms. These metabolically related organisms associate with their preferred substrates and produce the myriad of enzymes necessary for the digestion of chemically and structurally complex plant tissues. Upon accessing the internal, enzyme-susceptible tissues, microbial "digestive consortia" attach to a variety of nutrients, including protein, cellulose, and starch and digest insoluble feed materials from the inside out. Substances that prevent microbial attachment or promote detachment (e.g., condensed tannins, methylcellulose) can completely inhibit cellulose digestion. As the microbial consortium matures and adapts to a particular type of feed, it becomes inherently stable and its participant microorganisms are notoriously difficult to manipulate due to the impenetrable nature of biofilms. Properties of feed that place constraints on microbial attachment and biofilm formation can have a profound effect on both the rate and extent of feed digestion in the rumen. Developments in feed processing (i.e., chemical and physical), plant breeding, and genetic engineering (both of ruminal microorganisms and plants) that overcome these constraints through the promotion of microbial attachment and biofilm formation could substantially benefit ruminant production.
对瘤胃及其内容物进行直接显微镜检查发现，微生物群体大多附着在消化物中的饲料颗粒上。大多数饲料都有一层抗附着的表面层，因此也抗消化。通过损伤部位或通过集中的酶攻击渗透这些顽固的表皮层对于启动消化过程至关重要。初级定殖细胞的增殖产生了被糖萼包围的微菌落。来自瘤胃液的次级定殖者与微菌落结合，导致形成多物种微生物生物膜。这些代谢相关的生物体与它们偏好的底物结合，并产生消化化学和结构复杂的植物组织所需的大量酶。一旦接触到内部对酶敏感的组织，微生物“消化群落”就会附着在各种营养物质上，包括蛋白质、纤维素和淀粉，并从内向外消化不溶性饲料原料。阻止微生物附着或促进其脱离的物质（如缩合单宁、甲基纤维素）可完全抑制纤维素消化。随着微生物群落成熟并适应特定类型的饲料，它会变得固有稳定，并且由于生物膜的不可穿透性，其参与的微生物极难操控。对微生物附着和生物膜形成有制约作用的饲料特性，会对瘤胃中饲料消化的速度和程度产生深远影响。饲料加工（即化学和物理加工）、植物育种以及基因工程（瘤胃微生物和植物的基因工程）方面的进展，通过促进微生物附着和生物膜形成来克服这些制约因素，可能会给反刍动物生产带来巨大益处。
