To provide a lactic acid bacterium that can suppress butyric acid fermentation in silage or a fermented feed raw material which has low sugar content and which exhibits no sufficient fermentation quality by a conventional lactic acid bacterium, whereby high-quality silage or a high-quality fermented feed can be consistently prepared.The invention provides a lactic acid bacterium that produces nisin in a grass broth medium having a mono- and disaccharide total content of 0.1 to 0.4 mass% at a concentration of 40 IU or more per mL of a supernatant of the medium a microbial additive for preparing silage, which additive contains the lactic acid bacterium and a method for preparing silage or a fermented feed, the method employing the microbial additive.
