I would try a few things to get your dog to eat his food. Only feed him at designated times. Do not leave the food out all the time. This will create a sense of urgency to eat when food it provided....
You can go to PetSmart and buy a doggy gravy to put on the dog food. Or when you cook meat you can drizzle a little grease on the dog food and stir it. It can thicken up your dog to if it needs to...
Dogs really like people food & should be fed it every now & then. Vegetarian dog food is the BEST! Dogs are NOT carnivores! Well nutritional common sense is however necessary. It should be...