It is possible to classify the carbohydrate fractions of plants incorporated into animal feed into two groups : (i) those that are hydrolysable by the endogenous intestinal enzymes of the animal (these polysaccharides are located predominantly within the plant cell); and (ii) those that are hydrolysable only by enzymes produced by the microbiota (these are principally cell wall polysaccharides and are considered in more detail in Chapter 5). The former can be further separated into two main groups : first, the simple sugars and oligosaccharides represented mainly by the starches (contributing 100-250Kg-2). The structure and digestion of starch are described later in this chapter. First, the digestion of simple sugares and oligosaccharides are considered.