Zend_Db_Table is not a model class and never should be used strictly as a model class. It may seem convenient to work directly with the table classes in your controller but will only get you in trouble in the end. You should either construct your own model classes which use Zend_Db_Table or you can read this: http://www.zacharysnow.com/2008/06/20/zend_db_table-as-a-model/ for a semi work around.