4 day old canine runt

Question
Our normal vet is out and we cannot reach him. Our neighbors dog had 9 pups 3/31/08. They are a mix breed, mom is a mix of collie and chow, unsure what the dad was, he just happened into the denced in back yard and surprise. We were checking on the litter and noticed the runt was being pushed around by the larger pups, the mom seemed to push him out of the way and he was very cold. We brought the pup home, weighed him at 4oz, placed him in a box with heating pad on low, few layers of old towels and wrapped him up. Began feeding him puppy milk every 2 hours. He seemed much better, was eating between 0.5 and 1 oz every 2 hours and he was staying warm. We re-introduced him to mom yesterday and she took right to him. We have been checking on him frequently. Today he seemed weak and very hungry, but his body temp seemed ok just by holding him. We brought him back home weighed him at 9-10oz and began bottle feeding again, same routine. Tonight while stimulating him to void, he seemed to have a pink pus discharge from penis. This was not a large amount, but we are concerned. Is this normal for a pup 4 days old? Also, is it ok to bring him in every other day or every few days to supplement his feeding?

Answer
You may want to just remove this dog from the mom altogether after he is about one lb which is he almost there. She will accept him as long as he feels like he will live to her sensitive nose and instincts and that included being warm and active. When they get cold and listless the bitch will discard or reject a puppy they don't think will live because she knows she needs to put her energy to the healthy pups.

What you are doing now is good and the fact that he has gotten milk from her right away is to his long term benefit. The discharge from his penis could be just that he had some mucous build up in there from her not licking him enough to void. Keep that up too and it should clear up.

As I said before, he may do better if he is just hand raised and fed on formula if he can't hold his own with the mother. You could feed him and then take him back after his feedings every day. What you are doing right now is working so it seems to be fine.
I hope the mom is a nice mix of chow and collie since the chows we see here are really vicious.
Good luck with the little guy and keep me informed on his progress.