The most common mistake with a new food is changing too much at once. A dog or cat has a population of gut bacteria that is used to the old food; a sudden swap gives them no time to adjust. The result is often a loose stool, a picky week, or a return to the old food with the conclusion that the new one “did not agree”.
A ten-day switch
We use a simple schedule: one quarter new food for three days, half for three days, three quarters for two days, then all new. If the animal is sensitive, stretch each step to five days. Mix the food thoroughly; a dog can pick out the old pieces if you let them.
- Days 1–3: 25% new, 75% old
- Days 4–6: 50% new, 50% old
- Days 7–8: 75% new, 25% old
- Days 9–10: 100% new
Write down the start date
It sounds fussy, but a note on the fridge is useful. If something changes a week later, you know how long the food has been in the bowl. It also stops the “we changed it ages ago” conversation with your vet, which is usually followed by “how long is ages?”
What to watch
A little softer stool on the first day or two is common. Repeated diarrhoea, vomiting, blood, or a dog who stops eating is not something to wait out. Stop the switch and speak to your vet. If your animal has a diagnosed condition, ask them for a plan before changing anything.
Slow is not a lack of confidence. It is the cheapest way to find out whether a food suits them.
Treats count too
A new treat can cause the same upset as a new food. If you are testing a food, keep the treats boring for that week. Once the food is settled, introduce one new thing at a time, with a few days in between.
If you are not sure which food is right, bring the label and a note of what your animal currently eats. We will not diagnose anything, but we can help you compare the ingredients without the marketing language.