You bought a better food. Your dog has had diarrhoea for four days. You have concluded the new food does not suit your dog and gone back to the old one.
Most of the time, the food was fine. The transition was not.
Why sudden changes cause trouble
Your dog's gut carries a microbial population adapted to what it has been eating. Those organisms have specialised in the particular proteins, fats and fibres arriving daily.
Change the input overnight and that population cannot process the new material efficiently. Undigested substrate ferments, which produces gas, cramping, and water drawn into the gut, loose stools.
Give it a week and the population shifts to match the new food. That is the whole mechanism, and it is why speed is the variable that matters.
The seven-day transition
| Days | Old food | New food |
|---|---|---|
| 1-2 | 75% | 25% |
| 3-4 | 50% | 50% |
| 5-6 | 25% | 75% |
| 7 onward | 0% | 100% |
Slow down if stools soften. Hold at the current ratio for three or four extra days rather than continuing to the next step. A transition that takes twelve days and works is better than one that takes seven and fails.
Take longer, ten to fourteen days, for:
- Puppies
- Senior dogs
- Dogs with a history of digestive sensitivity
- Dogs recovering from illness
- Any switch between very different formats: kibble to fresh, fresh to raw, dry to wet
When you have no choice
Ran out, travelling, the shop is closed, the brand is discontinued.
- Feed smaller portions more frequently for the first two days, a quarter portion four times rather than half twice
- Add plain cooked pumpkin, which genuinely helps stool consistency
- Expect two or three days of softer stools and do not panic
- Get back to a proper transition as soon as some of the old food is available
Distinguishing a transition problem from a real intolerance
This matters, because getting it wrong means abandoning a food that would have suited your dog well.
| Transition upset | Genuine intolerance | |
|---|---|---|
| Timing | During the switch | Continues after full transition |
| Duration | Settles within days | Persists for weeks |
| Signs | Loose stools, some gas | Loose stools plus itching, ear problems, vomiting |
| Resolution | Resolves on its own | Only resolves off the food |
The test is simple: complete the transition, then wait two full weeks. If your dog is settled at day 21, the food is fine and the switch was too fast. If problems persist beyond that, it is worth investigating properly.
How often should you change food?
There are two reasonable positions and both are defensible.
Consistency: one food, unchanged, so that any digestive change is meaningful information. Easier to spot problems, easier to run a diet trial later.
Rotation: varying protein sources every few months, on the reasoning that a broader range reduces the odds that a single deficiency compounds, and keeps the dog accustomed to change.
Either is fine. What is not fine is switching every few weeks in response to every soft stool, which never gives any food long enough to be judged and keeps the gut permanently mid-adjustment.
If you rotate, transition every time. The seven-day rule does not stop applying because you have done it before.
Practical points
Check the calories. Foods vary from roughly 330 to 420 kcal per 100 g. Feeding the same weight of a denser food is an unintentional 20% increase, and the resulting weight gain gets blamed on the food rather than the arithmetic.
Store it properly. Fat in dry food goes rancid, and Indian heat and humidity accelerate that considerably. Sealed container, out of the sun, and buy bag sizes you will finish within about six weeks.
Introduce one thing at a time. Changing the food and adding a supplement in the same week means you cannot attribute whatever happens next.
The bottom line
Seven days, a quarter at a time. Longer for puppies, seniors and sensitive dogs. Slow down rather than push on if stools soften.
And before you write off a new food, complete the transition and give it two more weeks. Most foods condemned as "not suiting my dog" were simply introduced in a day.
Loose stools that continue well past the transition are worth working through properly rather than solving with another food change.