I've had some nibble young shoots, which can be frustrating. But when the hops get going, they don't have much use for them, at least where I live. Granted, I don't have a huge rat problem but they tend to find other things in my yard (cherry tomatoes, for example) that they prefer. I can't see how ten acres of hops could get overrun by rats. Maybe some owl boxes around the fields would be worthwhile...they'd be easy to mount on the poles. Good luck!