Switching your pet's food seems simple. Buy new bag. Pour new food. Done. Except that's usually when the diarrhea starts. Or the vomiting. Food transitions are one of the most common reasons I see upset stomachs in otherwise healthy pets, and it's almost always preventable. Mixing old and new food together in gradually shifting ratios is the safest way to transition without upsetting your pet's stomach. Photo: Unsplash Why Gradual Transitions Matter Pets have sensitive digest