Has the dog's favorite person left the house for a while? This could be the cause. Also, have you changed the food recently, or any of the dog's routines? These might all be factors as to why he or she isn't eating.
Any dog may lose their appetite and refuse to eat for a large array of reasons. Illnesses, digestive upsets and discomfort can cause the dog to lose their appetites.
There are any number of reasons why your hound is not eating. You should take him to the veterinarian immediately. It could be just some stomach discomfort, a broken tooth, or any number of even more serious problems. You should discuss this with your vet.
This could be many different things, maybe he dosen't like the brand of food, also he might be lonely , spoiled or have a gasey stomach. Try a good protein diet, and see if he'll eat that. It's a trial and error deal.