Causes of dogs’ loss of appetite:

1. Emotional reasons. Dogs may experience anxiety and stress in their daily lives, especially since they are sensitive to their owners leaving and often develop separation anxiety, which can lead to loss of appetite.

2. Indigestion. Certain foods can cause constipation or diarrhea in dogs, causing them to feel gastrointestinal upset so they don't want to continue eating.

3. Parasitic infection. Parasites that live in a dog's gastrointestinal tract will affect the dog's gastrointestinal health. The dog's loss of appetite is likely to be caused by parasitic infection.

4. Picky eaters. Some dogs only like to eat meat but not dog food. If there is no meat, they will not eat dog food. Or eating too many snacks makes them picky eaters.

5. Sickness. Dogs will also lose their appetite when they are sick and feeling unwell, such as pain, fever, etc.