摘要
Animals consume food consisting of a complex matrix containing both simple molecules (free sugars and amino acids, etc.), and macro-molecules such as structural carbohydrates, protein and lipids. For the most part, simple molecules require little modification before they can be absorbed from the digestive tract and utilized by the tissues. However, macro-molecules almost always require dismantling into their simpler building blocks before they can be absorbed across the intestinal wall. Digestion is the process by which these dietary macromolecules are broken down. This is followed by absorption of digestive end products across the wall of the different compartments of the digestive tract, and their distribution to body tissues via the blood stream.
摘要译文
动物食用含有简单分子（游离糖和氨基酸等）和大分子（如结构碳水化合物，蛋白质和脂质）的复杂基质组成的食物。大多数情况下，简单的分子在被消化道吸收并被组织利用之前几乎不需要修饰。然而，宏观分子几乎总是需要拆解成更简单的构件，才能被肠壁吸收。消化是这些饮食大分子被分解的过程。接下来消化终端产品通过消化道不同隔室的壁吸收，并通过血流分布到身体组织。
J. M. Chesworth12;T. Stuchbury1;J. R. Scaife1. Digestion and Absorption in Ruminants and Non-Ruminants. An Introduction to Agricultural Biochemistry[M].DE: Springer, 1998: 395-411