Our vet told us once that the most important thing in dealing with a sick chicken is that they continue eating. We don't do this often, but we took a favorite sick rooster to him once, and that is what we ended up doing; force feeding him as much as he could stand...and he was eating, too. The oatmeal/vitamin mixture would be a good idea; the vet gave us some sort of green baby-food texture stuff that was a powder and you mix it with water. The vet told us, absolutelyl, to go out of our way to give him whatever he would be tempted to eat. Actually, if oatmeal doesn't work, you might try force feeding babyfood and vitamins with a syringe. And, by the way, our rooster recovered, although, of course, he had meds too in addition to his extra food.