If your dog receives a clean bill of health, the next step is to evaluate the food you feed. Begin by assuring that the food has not spoiled. Both dry and moist foods can expire, and it is also possible to buy a bad batch of food. Check the expiration date and take note of any odd odors in the food.
You should be feeding a high-quality, nutritious diet which your veterinarian has approved. A quality brand of food will supply your dog with all the nutrients he needs, eliminating the need for diet variety. Dogs do not need variety in their meals like humans, because they have all the nutrients they need in their dog food.
Consistently feed one type of food. Constantly changing foods may cause your dog to hold out for something tastier, creating a finicky eater. Change can also cause vomiting and diarrhea in some dogs. Feeding human food snacks can have the same affect and can also lead to obesity.
For more information, please read How to Encourage Your Picky Dog to Eat