I've always understood "domestication" to be something that happens to a species or a breed, the point being that the animals themselves are changed (not in a Lamarckian way, but through selective breeding, either consciously or unconsciously). Thus, a chicken is a domesticated jungle fowl, a dog is a domesticated wolf, and so on. I think that when you're talking about wild animals that are tamed, the term "domestication" is used loosely when this is done habitually, as with elephants, so we can talk, in a sense, of the domestication of elephants, even though there is no domestic breed of elephants. Zebras, of course, can't be domesticated in either sense, because they cannot usually be tamed in the first place. But I'm not going to start on that again.
If you think arguing about semantics with a semiotician is bad, just you try it with a philosopher.