PURPOSE:To enable the production of a large amount of high-quality fur or wool, by feeding ''Bacillus natto'' as an active ingredient to animals. CONSTITUTION:''Bacillus natto'' as a quality improver for fur or wool is added to a feed and fed to animals, e.g., sheep, rabbits, minks, whose fur or wool is useful for spinning and weaving or as a fur material. The amount of ''Bacillus natto'' used varies with the kinds of animals, other ingredients of the feed, etc., and generally about 10 -10 ''Bacillus natto'' per day is added to the feed in feeding.