A Hard Belly May Be Caused by Overfeeding
If a dog's belly feels hard and the dog seems listless, one possible cause is that it ate too much. Dogs have little sense of fullness and may keep eating whatever the owner provides. Because their digestive ability is not as strong as a human's, overeating can lead to food stagnation in the gut and gastric bloating. In this case, digestive probiotics may help, and daily overfeeding should be avoided.

A Hard Belly May Be Caused by Constipation
A dog that seems dull and has a hard belly may also be constipated. Dog food can be dry, and if the dog does not like drinking water, constipation can develop. The stool becomes dry and difficult to pass, then builds up in the intestines. The owner can encourage the dog to drink more water, gently massage the abdomen, and help with bowel movement when necessary.
A Hard Belly May Be Caused by Intestinal Disease
A hard belly can also point to gastrointestinal trouble. Parasites in the digestive tract may be involved, or the dog may have swallowed a foreign object that has become stuck. Owners should deworm the dog regularly, care for its digestive health, and take it to a veterinarian promptly if it looks very uncomfortable.

How to Prevent a Hard Belly in Dogs
Do not feed only dry dog food all the time. Vegetables such as spinach and carrots can be chopped and mixed into the food in appropriate amounts. Make sure the diet remains balanced, with adequate vitamins and calcium. If the dog does not like to drink water, a little water can be mixed into the food. In addition to proper feeding, the dog should get regular exercise, sunlight, and routine deworming. A stronger body naturally means better immunity.