First, overeating, food piled up in the intestine is difficult to digest, you can give the dog a day of fasting, and feed the right amount of probiotics to help the dog digest.
Second, eat more beans. When beans are decomposed by bacteria in the intestine, it is easy to produce various gases, causing flatulence.
Third, it may be caused by some diseases, such as parasites, ascites, flatulence and abdominal tumors. You need to take it to the pet hospital for examination and treatment in time.