Mannan-oligosaccharides (MOS) maintains the wellbeing of the bacterial flora of the intestines. MOS is also capable of binding the adverse substances in feed. Live yeast assists in the generation of beneficial microorganisms, and promotes the digestion of fiber. Brewer's yeast support the wellbeing of micro-organisms. Yeast booster is suitable for horses with problems with feed conversion, and during periods when the activity of the intestines is endangered.