Let me explain. I already safari netted them and took them to where I want them. I then leashed them to a post so they could start working for me. If it's a chunkloading issue though, then would loading the chunks that they are in minimise it do you think?
In my experience, mostly with horses, leashes break when the chunk holding them becomes loaded from an unloaded state. That said, even when I had chunkloaded the area (usually ChickenChunks), I still experienced some breakages, seemingly at random. I "solved" the issue by fencing the area around my hitching post in, while begrudgingly accepting that it was an issue with the base code that wouldn't be updated away. I'm curious now if it was fixed in 1.8.
I know its not what you wanted to hear. Chunkloading an area you will only visit to reset their position is probably for the best, as they should work in a loaded area, and the leash doesn't seem to break until the player loads the chunk. Hope that helps you some.