Well...That's a bit extreme. They are animals and not humans, after all. Animals are killed in the thousands every day just to feed us, for example....WE can't send all those people to jail, there wouldn't be anymore steaks or chicken dinners or pork loins.
But for the cruelity such as you describe, they should at least get the 'Michael Vick' treatment, only without the big NFL contract after they get out. 3 Years minimum for the first offense, and more for repeat offenders. And for sure, make them a Felon.