I usually have major slowdowns while playing this game. It doesn't need…

I usually have major slowdowns while playing this game. It doesn't need to have lots of animals around. When the bears come, it gets worse, but when they leave, sometimes it gets a little better. The earlier stages didn't slowed down at all but it's getting progressively worse. I'm at the stage where you start with a cow and it's almost unplayable. Anyone have a solution for this?