If you switch dog food suddenly, it can definitely cause tummy troubles with your dog, causing constipation or diarrhea or even vomiting. To prevent any intestinal problems, here is how you should switch food to introduce the new food to the diet gradually. And yes, this even counts when switching from puppy to adult food or adult to senior food.

First day
Feed 75% old food type with 25% new food.

Second day
Feed 50% old food type and 50% the new.

Third day
Feed 25% old food type and 75% new food type

Fourth day
100% new food

If you notice any tummy troubles, you can increase the switch time, adding 10% of the new food type while decreasing the same amount over a ten day period instead.

It is also important to not try and do the food changeover during a time that is stressful or traumatic for your pet. If you have just adopted the puppy or dog, recently adopted a new one, got married, had a baby or do anything else that could stress the dog, you are best to wait to change the food until the stress is passed. The last thing you want to worry about is a dog that has stopped eating because you changed from his favorite food the same week you brought home newborn twins from the hospital!