Slavery is a system under which PEOPLE are treated as property and forced to work.
If we were to extend this definition to animals, it seems to me all you dog owner's reading would be slave owners (making poor Fido roll over and sit and catch a ball without due compensation).
And maybe even us cat owners, although anyone who has ever owned a cat knows that it is certainly a matter of debate as to who owns who (or is it whom)?
But come on, Ann-slavery?
Just because they made a cute little movie with a Michael Jackson song (Free Willy-remember?), everybody thinks killer whales are the mistreated foster children of the aquatic world.
That's right, Blackfish, you were twenty years late to the party!
The point is, based on the picture below, both trainer and whale appeared content with their relationship.