I agree with the comment about the food being served heated up. I also have good experiences with adding some garlic to my dog's meals (but be careful, keep reading!).
My lab mix had suffered from a loss of appetite (It wasn't Cushing's back then, as far as I know, it was due to a bacterial infection, but might be worth giving a shot) and I've added a small amount of garlic to some of his meals and I must say it worked (although I was quite a sceptic about that advice when I first got it).
But ask your vet about that or try reading about the amount you can use in his/her meals since garlic can be poisonous for dogs in case it's not dosed properly. Please mind that it's just an advice based on my personal experience!