[suzannex3]

We live in a remote area with 10 acres. Three years ago we adopted a neutered chocolate lab/Cheasepeake mix. He has always been devoted to us, especially my daughter. We have a fence, but occasionally let our dogs out, as they are trained (or were) to come on commands. A few months ago, my BIL adopted a stray cur mix. A beautiful, and sweet dog to humans, but aggressive to other animals. Since then I've noticed our lab mix also becoming aggressive to other animals when around her. since her adoption, my nephew has moved back home and brought his male boxer. (They live near us.) I regret that our lab got out and ran with them. we ended up with a tragedy. They have attacked our mini pony! NEVER before has our lab mix even attempted this. We realize that we can no longer let him run the ten acres unless he is leashed. I'm worried that this behavior cannot be reversed. I don't know what to do. With us and our doxie, he is as laid back and passive as can be. Will I have to put him Down? Thanks