Hope your puppy is doing OK now. Canned goat's milk is a great alternative for puppies who are rejected by their mothers. A friend of mine kept an entire litter of rotties alive by bottle-feeding goat's milk every 2 to 3 hours. The mother not only rejected them, but tried to kill them. Unfortunately, this behavior happens sometimes. Other times the mother rejects a pup because something is very wrong with the puppy and she knows it won't live.
Most babies will eat until there full.When they are nursing it is really hard to say how long.You could try asking your vet and see what they say.How long does the baby want to nurse each time?