Poplar or pine sawdust is used to main substrates for oyster mushroom bottle cultivation. However, sawdusts are containing a lot of lignin that is insoluble and non digestible component. Therefore, spent substrates which are produced by oyster mushroom harvest are difficult to use as ruminant feed. In this study, we carried out to find sawdust substitute on the oyster mushroom for ruminant feed. As results of chemical analysis of cotton seed pellet, corn stem pellet, and corncob was revealed that concorb showed low crude ash(2.4%) and lignin(13.1%) contents. Mushroom yield and biological efficiency in concorb substrates is similar to and higher than that of control. Therefore we estimated that corncob could be substituted for sawdust.