The use is provided of a composition as a feed additive which comprises one or more endoglucanases, and 0-20% by weight, based upon the content of cellulase proteins in the composition, of a cellobiohydrolase. The endoglycanases may be one or more of EGI, EGII EGIII and any functionally active derivative of any thereof. Such endoglucanases may be obtained from a genetically modified strain of the fungus Trichoderma. Also provided is an enzyme-based feed additive which comprises EGI and/or EGII which lack the cellulose binding domain, and 0-20% by weight, based upon the content of cellulase proteins in the additive, of a cellobiohydrolase. A further enzyme-based feed additive is provided which comprises a cereal-based carrier, one or more endoglucanases, and 0-20% by weight, based upon the content of cellulase proteins in the additive, of a cellobiohydrolase. Such enzyme-based feed additives can be incorporated into a cereal-based feed which includes one or more of barley, wheat, tricale, rye and maize. The feed additive has the advantage of improving the feed conversion ratio and/or increasing the digestibility of a cereal-based feed in which it is included.