You could also add a little bit of shredded cheese to his food. What about peanut butter in a kong? My pup loves that... I freeze them so it takes a bit longer to get it out.
I would ask your vet about the nutra-cal. Ella was on it the first few weeks i had her and it was the only way she would eat at all. I am not sure if it is good to use every day, but then again, I don't see why not until he gets his weight up. Maybe once a day or once every other day?
Hope he gains weight soon!
