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 digestive microbiota (these are mainly cell-wall polysaccharides and are considered in Chapter 5). The former can be further separated into two main groups: fist, the simple sugars and oligosaccharides, which are present at low levels (<50 g kg−1) in rabbit feeds; and second, the polysaccharides represented mainly by the starches (contributing 100–250 g kg−1). The structure and digestion of starch are described later in this chapter. First, the digestion of simple sugars and oligosaccharides are considered.