Sometimes the respirator tube can cause a pretty sore throat and the dog might avoid eating because of it. If you suspect this, you can try and push warm liquids like chicken broth or chicken and rice soup to help soothe the throat.
I would keep an eye on it. The biggest concern when a dog has surgery is that they will aspirate during the surgery and this can cause aspiration pneumonia which is very serious.
I would also try to get some pedialyte or gatorade in him in case he dehydrates. You can syringe it into the mouth if you have to (no needle!).
If you don't start to see this resolve, you will want to give your vet a call when on Monday.
Let me know if you have more specific questions or if you want to discuss this further.
Edited by tfalkner on June 18 2005 at 11:12 PM