So, you want to start a new diet, or your vet has sent you home with a new food, but you’ve been told to transition slowly. What does that even mean!? Transitioning simply means phasing out one food while gradually adding in the new food.

“But why,” you may ask, “I don’t transition when I eat something new!” No, but humans normally eat a highly varied diet and are generally quite well adapted to this, however if you’ve ever been to a foreign country, you might notice the local cuisine doesn’t necessarily agree with you! The reason for this, once again, has to do with the gut microbiome; recent studies have shown that what we eat (aswell as what animals eat) determines the types and species of microbes we have in our gut – people in Japan have microbes adapted to handling alot of seafood and fermented foods, whereas people from India have microbes who are better adapted to digesting spicy curries. These microbes are adapted to digesting certain types of foods they are most commonly in contact with and typically work symbiotically with us when everything is in balance. When you suddenly change what you eat, the microbes don’t know what to do, it isn’t what they are used to digesting and they don’t have the tools to work their magic on that food. This usually results in diarrhea and GI upset in the host.

When you transition, you are allowing time for new microbes, carried on the food to enter the system and populate the gut, progressively ‘warming up’ to deal with the change occuring. This is mainly to prevent the unfavorable results of a quick change such as diarrhea or vomiting.

When should I transition?

If you are planning on changing your pet’s diet, we usually recommend a seven day transition period. When you get down to the last few servings of the old food, you can start introducing the new food. You’ll often see a picture like below on the packaging, explaining how you need to do this.

Essentially, you want to add about a quarter of the new food into the daily serving, and reduce the amount of old food by a quarter. Gradually increase the amount you are adding of the new food, and gradually decrease the old food each day for seven days. If you notice any diarrhea or vomiting during the transition, don’t increase the new food, just maintain the current mix for a few days until the symptoms resolve, then you can continue increasing the ration.

The seven day transition period is NOT one size fits all; animals with allergies, GI issues, skin problems or chronic conditions may need a slower transition. In these cases, your vet will advise you on how long to transition for; often the slower the better. If your pet’s current food has been identified as the cause of their condition, or a change needs to be made quickly for whatever reason, the transition period can be skipped all together.

They won’t eat the new food!

The other reason we recommend a slow transition is that the most common cause of food refusal in animals is a sudden introduction of the new food. Cats especially like the same food day in day out, and any change – not just in their food but also environment, stress, negative event, moving food bowls, using new bowls etc – can cause refusal. This is called food aversion; when the animal associates the food with a negative event such as a hospital stay, illness, or even a person they don’t like that they then relate to that food and refuse to eat it. This is why we do not feed the food your pet gets at home when they are in hospital, and will instead send you home with a recommendation to slowly transition to the new (usually therapeutic) food. In these instances, it’s very important to try and transition for the best chance of success for your pet to accept the new diet.

Has your pet ever refused to eat a new food? Tell me about it in the comments below!