Actigen is a pre-biotic-type product from Alltech.  It is a feed additive that is derived from Yeast cell walls (usually from a specific strain of Saccharomyces cerevisae).  The cell wall of yeast is made up of many protein, carbohydrate and lipid-based components, including saccharide (sugar) structures called “mannanoligosaccharides (MOS).” MOS protrude from yeast cell walls and are involved in cell-to-cell communication.  MOS is considerewd to be a prebioticbecause it is not broken down by the host animal’s digestive system enzymes but can be used as a food source for beneficial bacteria that inhibit the natural flora of the digestive tract.