Poor baby
I'd go ahead with the pumpkin, it may help slow things down a bit so he can re-hydrate. Make sure he's getting lots of water, or some Pedialyte if you have it on hand. The pumpkin has no fat, so it won't make the situation worse. Is he vomiting also? If he is, I would only give him water for now until the vet can see him.
BIG hugs to you and your Bubba
