I have a litter of 5 puppies born within the last 24 hours. I just noticed one puppy has foamy stool while nursing. Mom and puppies seem happy and content.
Should I be concerned?

I would call the Vet and ask them.

Actually I find that foamy stools are typical of the first few days of nursing - it takes wee ones a few days for their digestive systems to get in sync and digest the milk properly.

Thanks. . .

Try a little Benebac