Most of the digestive upsets we hear about after a food change were not caused by the food. They were caused by the speed of the change.
Somebody buys a better bag, gets home, and swaps the whole bowl that night. Two days later the dog has loose stools and the new food takes the blame. It goes back on the shelf, the owner concludes their dog cannot handle raw or cannot handle lamb, and a perfectly reasonable food gets written off for the wrong reason.
Stella's own instruction is seven to ten days. Mix the new food with the current one, increase the new and decrease the old across that window. Nearly every manufacturer says some version of this, including ones whose foods sit nowhere near each other on our shelves at 1288 Highway 33, and the consistency across brands tells you it is not marketing.
Here is why the window matters, in plain terms and without pretending we can diagnose anything. A dog's gut is populated by an enormous bacterial community, and that community is shaped by what it has been fed. Change the input abruptly and the population has to catch up. Change it gradually and it has time to. That is as far as we will go, because what happens inside a particular dog is a veterinary question and not a pet store one. If your dog has ongoing digestive trouble that is not about a food switch, that is a conversation for your vet rather than for us or for a bag.
The practical mistakes we see are not about the concept. They are about execution.
People count the days but not the amounts. Seven days of ninety percent old food followed by one day of all new food is not a transition, it is a delay. The ratio has to actually move.
People also transition and add a topper at the same time. Now two things changed and if something goes sideways you have no idea which one. Make one change, let it settle, then make the next.
And people forget that freeze-dried is concentrated. Going from kibble to something like Stella's Super Beef dinner patties is not just a flavor change, it is a change in how much food volume delivers the same calories. Stella's charts account for that, but only if you read the chart rather than matching the old scoop.
Where the usual advice does not apply: a dog with an actual diagnosed condition, a dog on a prescription diet, or a dog your vet has given specific instructions about. Follow the instructions you were given, not a blog.
Our opinion, and it costs us sales to say it. If you are switching foods because the current one is working fine but something shinier caught your eye, consider not switching. Dogs do well on consistency. The best food is frequently the one your dog has eaten happily for two years. Novelty is more interesting to owners than it is to dogs, and the aisle is designed to make you feel otherwise.
If you are switching for a real reason, give it the ten days rather than the seven. The extra three cost nothing.
Write the start date on the new bag with a marker. In a week you will not remember which day you began, and that is usually when the math goes wrong.