Not sure if I should post this here but I have a 9 year old miniature dachshund who is great with everybody and every animal he has come across but when we brought our newborn home 6 days ago he has done nothing but try to bite and nip him. He doesn't growl, he wags his tail but I swear I can see a change in his eyes. I don't trust him and so we bought him a muzzle and I still don't trust him. What can I do? How long should I give him before I make the very difficult decision of rehoming him? Also he was 3 when we brought home our daughter 6 years ago and had no issues what so ever. Please help me: