Animals may not go to heaven, but they go somewhere and it's a good place.
I'd like to think that they do, as I've had several very special friends throughout my life that I look forward to seeing once again some day.
Having to make the decision to relieve the pain of one that you love is one of the hardest things that we will ever do. The void and mental anguish that you feel right now will gradually diminish, yet your positive memories of OZ shall remain.
Jim