Most animals don't give a hoot about helicopters
Don't you believe it!
Sheep will usually move away(in a bunch as you would expect), at varying speeds.
Cows will generally ignore you if not too close, but young ones can get a bit skitish.
Horses are by far the worse. Unless they are used to helicopters, they will generally go crazy, and will easily crash through a fence to get away. Avoid them like the plague.