Had this problem when a stray I took in had a litter, I took on feeding him and he got alot stronger as time went on. I never left his side

I don't by the vet 'destined to not survive' either. Yes in the wild some won't survive because they all fight for milk and food but in a environment were humans are here and helping they can survive and I proved the vet wrong with Elvis who now lives a happy normal life in a family and has no problems. Is he warm? Make sure he is nice a warm, feed him with the milk every 2 hours. I used Sherleys Lactol and they have specially designed feeding tubes, have a look in your local pet shop or pets@home. If he is a fighter he will survive but if he doesn't he tried and so did you. xxx