An additive for stock feeds containing decomposition products of chicory roots in which the total content of polysaccharides and inulooligosaccharides of tri- and higher saccharides obtained by decomposing the chicory roots is 40% by weight or more of the total solids content and is 80% by weight or more of the total saccharides. The stock feed preferably contains 0.1 to 10% by weight of the additive. The additive is prepared by a process which comprises the steps of chopping and then heating/drying chicory roots in order to form chicory flakes, and grinding the chicory flakes, or by a process which comprises the step of enzymatically decomposing the chicory roots without an extraction step.