You indicate that it is his fence....That is, the fence was constructed by him and was on his property. Is that correct? He is responsible for removal of the fence from your yard, but isn't likely bound by your desire to repair it. How old is the fence? How much would it cost you to put up a fence in your yard that would satisfy your need to contain your anomals?
You say he hasn't responded to registered mail, but somehow know he wants a new fence. Perhaps just sit down with him and work it out? If he doesn't want to do something that is acceptable to you, maybe ask him to remove his fence and you can put up one on your property to satisfy your needs.
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