What’s the theme of the oxen the wheels

normally working animals are domesticated and ruled by a master, a domesticator (tamer), to perform basic and important functions on a farm, for example. the value used in this context is animal labor in exchange for food. it is not so much a contrast to the story told by napoleon and the pigs, since the animals of that particular farm also performed functions on the farm through domestication. the only thing is that in this case, who rules them is a pig, also an animal, but very respected, to whom the other animals lent him submission. that's about a strong relationship of dependency between animal and owner.

  this riddles' answer is library.

  the "leaves" are a reference to the books' pages that the library contains; the branches are a network of libraries that connect multiple libraries' collections, resources, and items in a system of a common database, integrating them; the branches' organization are a useful management tool for coordinating the multiple collections many libraries have.