When Roxy was really, really sick we ended up giving her baby food (she liked chicken and veal) and rice baby cereal along with her nutri cal. The rice really helps with their poops (if you can get them to eat it!)... but be careful with the nutri cal. It can loosen up their poop- Karo is a better alternative, or so says my vet...
But try getting a pup to take karo when they've tasted nutri cal...
good luck!
My baby is back to eating boiled chicken (no skin) mixed with baby food and supplemented with a/d and science diet canned foods. She hates her dry kibble still...