Abstract
Oligosaccharides are low molecular weight carbohydrates between monosaccharides and polysaccharides, which consist of 2 to 20 monosaccharides linked by glycosidic bonds. They have the effects of promoting growth, regulating immunity, improving the structure of intestinal flora, and are anti-inflammatory and antioxidant. With the comprehensive implementation of the antibiotic prohibition policy in China, oligosaccharides as new green feed additive have been paid more attention. Oligosaccharides can be divided into the following 2 categories according to their digestive characteristics: one is easy to be absorbed by the intestine, called common oligosaccharides, such as sucrose and maltose oligosaccharide; the other is difficult to be absorbed by the intestine and has special physiological functions, called functional oligosaccharides. The common functional oligosaccharides include mannan oligosaccharides (MOS), fructo-oligosaccharides (FOS), chitosan oligosaccharides (COS), xylo-oligosaccharides (XOS) and so on. In this paper, we review the types and sources of functional oligosaccharides, their application in pig nutrition, and the factors limiting their efficacy in recent years. This review provides the theoretical basis for further research of functional oligosaccharides, and the future application of alternative antibiotics in pig industry.