Thank you for that information, now it seems we have both posted at the same time!

First the dog vomiting after eating. This could be because he is eating the pups food or because he is eating his food too fast , or there is something wrong health wise that is causing this. Much will depend on how long he has been vomiting, IF it has only been a short while it may be from an obstruction of the bowel from something he ate that he should not have such as a bone, toy, raw hide, pig ear etc. So if the vomiting continues after you have kept him away from the puppy food then he should be examined. If he is eating or drinking too fast then this can cause vomiting but you would normally see this happen pretty quickly after he ate, not four hours later.

It maybe helpful to add a little warmed chicken broth as be enticing to a dog also and it should not upset the stomach too much, as well some boiled chicken which is used for dogs when they have upset stomachs.

If vomiting continues then I would be more worried this is a health problem such as an obstruction and would bring him back to your vet for exam or get a second opinion.

!5 lbs is a lot but if he is not able to hold anything down then I can see it happening especially if you are feeding him more than once a day. An obstruction would continue until the item causing the obstruction was taken out surgically, it will not go away on its own so if you know that he may have eaten a non food item then it's time for an x ray and sometimes even the stuffing from a toy does not show up on an x ray and they still have to go in surgically to look around.

Other symptoms may be a change in stool or stool habits and lethargy. Eventually anything he eats or drinks would not be able to stay down.