How do i get rid of lots of horses? [duplicate]

In Minecraft, my friend built a horse spawning system to get many horses of one color. When he was done, there were a lot of excess horses which are now roaming my land. The horses are causing frame rate issues, lowering my FPS.

The horses are spread out across the land. Is there a way that I can get rid of all the horses, without killing the horses I have in my stable?

In case anyone needs visuals on what the land looks like:

Solution 1:

What you can do is get the mod "Single Player Commands", in this mod, you can use a command called /butcher which you can use to kill mobs within a specified radius. I would say use a small radius and kill the surrounding horses that are further away from the stable. After that you can manually kill the rest. Also, the good thing about this mod is that you can back up your minecraft.jar and worlds so that you can then easily just uninstall the mod after you are done. If the above doesn't work then try fire...

Happy killing!