Some misunderstandings here.
HSM is to do with focus, not zoom. HSM is quiet and mostly quick. AF-S is the Nikon equivalent. Canon have the same deal.
Minolta lenses have no motors, except the very newest SSM ones. Nikon lenses only have a motor built in when they say AF-S on the lens, as all their new lenses do, otherwise the camera itself drives the lens, as in Minolta, with a screw.
HSM and AF-S lenses lenses are often much nicer and faster to focus than 'ordinary' lenses, they also allow instant manual override, meaning no switches at all, which is great. So it is actually a big deal if you have the option, but as you don't really have the option with Minolta, don't worry about it. You won't miss it on a slow lens like the 50-500.
The 50-500 is actually pretty good, even better for Minolta because of the AS system. However, the animals you shoot need to be chilling, becuase the lens is too dark and slow and cumbersome for predictive focus and whatnot.
Consider the 500/8 instead, for it is much lighter. But you have to mind the bokeh with that one.