Here are a couple of websites with recipes for sick dogs. Again, consult with your vet first. I don't know why your vet would prefer chicken to beef, since your dog will eat beef but not chicken. The first website has a meal with beef and rice. The second website has recipes that can use either chicken or beef. Both sets of recipes use cooked ground beef, not raw. I assume that's to keep the bacterial count down, which is important if your dog's immune system is compromised by the illness. I would only use the raw beef if your dog won't eat cooked beef and you have no other option.
Making Ground Beef and Rice for Dogs With a Belly Ache The bland sick diet for dogs! (What to feed your sick dog) - K9 Instinct - Dog Nutritionist in Kitchener, Ontario, Canada. K9 Instinct Blog! Dog Nutrition consultations online!