The carbohydrate ingested by the growing-finishing pig is mostly of the polysaccharide type. Since the young pig does not efficiently utilize polysaccharides, considerable amounts of the disaccharides, sucrose and lactose, and the monosaccharides, glucose and fructose, are used in baby pig diets. The disaccharides which are ingested are hydrolyzed to monosaccharides within the mucosal cells of the small intesine, from whence the monosaccharides are absorbed. Absorption of monosaccharides takes place readily only from the small intestine, and occurs predominantly by way of the portal blood (Wilson, 1962, p. 73). Limited absorption from the stomach and large intestine has been reported to occur under some conditions but it is quantitatively unimportant compared to absorption from the small intestine. Furthermore, it has now been adequately demonstrated that absorption of sugars from the small intestine occurs by both passive and active processes, the former being an energy-independent entrance of sugar into the cell, the latter an energy-dependent movement against a concentration difference (Crane, 1950). The nature of the active transport system has not yet been fully elucidated.