In Larry Niven's "Known Space" stories, one bit of backstory is that billions of years ago the Slaver empire colonized planets with yeast to feed to their lives

In Larry Niven's "Known Space" stories, one bit of backstory is that billions of years ago the Slaver empire colonized planets with yeast to feed to their livestock -- giant bioengineered slugs. In his "World of Ptavvs" he describes a survivor coming out of stasis on earth, long after the fall of the Slaver empire, very confused about what happened to his planet...