1. Dogs with severe gastrointestinal diseases: In fact, the best way for dogs with such diseases is to be hungry for a day. I've tried it, and it's very effective for big dogs and puppies. But after a hungry day, I still have to eat. At this time, the food you give should be mainly digestible protein and carbohydrates. Don't eat greasy food such as meat for the time being. Cooked egg yolk, rice, steamed bread or soaked dog food all belong to this kind of food. 2, loss of appetite caused by a cold and fever: this kind of dog has no problem with the stomach, but the loss of appetite caused by other diseases. At this time, they should make some food that can stimulate appetite, that is, food that smells delicious. You can scald it with minced meat or minced meat mixed in dog food, but the amount is less than usual, based on the principle of eating less and eating more meals. Because the digestive ability of gastrointestinal tract is still weak at this time, it is easy for dogs to overeat and cause indigestion. 3. Diseases caused by obesity: Obesity can cause many diseases. The diet of obese dogs is a problem that needs sustained attention. Foods high in fiber and low in calories are the first choice. Some foods made of corn flour and vegetables are suitable for this kind of dog, but they should be seasoned slightly, such as a small amount of broth, otherwise it is estimated that the dog will be killed and not eaten. 4. Malnourished dogs: This situation is rare among domestic pet dogs, but the stray dogs picked up from outside are different. They are likely to be malnourished. Of course, we should pay attention to supplementing nutrition to these sick dogs in diet. Fat, protein and carbohydrate should be supplemented, but it is also based on the principle of better digestion and less meals. In addition to eating dog food, you should add nutritious things such as chicken, chicken soup and bone soup to every meal, but you should remove the oil from the soup. Too greasy soup will cause their diarrhea. (Note: What you need to do is to deworm the stray dog and have a physical examination before strengthening the nutrition. Otherwise, it may not only hurt your original dog, but also waste the nutrition you added to it. Simply put: dogs with gastrointestinal problems should eat less; Sick dogs with nothing in their stomachs should be encouraged to eat more; Obesity causes sick dogs to eat low energy and malnourished dogs to eat high energy.