How to transition your pet to a new diet

There are many different reasons pet parents might need to change up what they’re feeding their furry companions. Puppies and kittens need to be weaned onto adult food. Pets with health conditions might need a special diet. Your pet’s old food might not be available anymore. Whatever the case may be, it is important to choose a food that fits your pet’s needs, figure out how much food your pet will require, and transition slowly to the new diet while monitoring them for digestive upset. 

Step 1: Body condition score your pet

Body condition scoring is an extremely important – and super simple – way that you can stay on top of your pet’s health. By learning how to score your pet, you can tell if they are at their ideal body condition; in other words, not too fat or too skinny. Finding your pet’s body condition score can help you choose a food that is right for them, and it will also help you calculate their calorie needs.

Learn how to body condition score here.

Fawn, 20lb, BCS 4/9 (ideal)

Step 2: Find a new diet

There are two parts to this step. First, you’ll want to find a pet food company that employs experts, has good quality control, and is based in science. Learn how to assess a pet food company here. 

Then, you’ll need to evaluate your pet so you can pick a food that meets all of their needs. The right food for your pet will fit their species, life stage, body condition, activity level, and health status. Learn how to assess your pet here.

Choose a brand that meets the WSAVA nutritional recommendations

Step 3: Calculate your pet’s calorie needs

An important part of feeding our pets is making sure they are getting the correct number of calories each day. Feeding too many calories can lead to weight gain and obesity, while feeding too few calories can lead to weight loss and malnutrition. Learn how to do the calculation here.

Step 4: Figure out how much old food is left

You’re going to want to make sure there is enough old food left so that you can gradually transition your pet onto the new food. Make sure there is at least one week’s worth of old food. Don’t start transitioning if there is too little food left; it might be safer to buy a small bag of the old food to make sure you won’t run out too soon into the transition.

Don't start transitioning if you're almost out of the old diet!

Step 5: Plan out meals for the transition

Here is a general outline of the portions your pet should get each day during the transition:

This is the most important step, because changing your pet to the new food too quickly can cause digestive upset such as vomiting and diarrhea. Some pets have more sensitive stomachs than others, and will require a longer, slower transition period. Some pets will do just fine if their food is changed gradually over one week. You know your pet best, so you’ll have to determine if a short-course or long-course transition is right for them. For a long-course transition, simply feed each “day” for several days in a row. Some cats can be particularly fussy, so “days” may turn into weeks.

First, you will need to know how much of the old food your pet is getting each day.

Then, determine how much of the new food your pet will need to eat once he or she is fully transitioned. This can be a volume (cups) or weight (grams), with weight in grams being more accurate. To figure this out, you can visit How to accurately measure your pet’s food.

Once you have these measurements, you will multiply them by the percentage your pet needs each day during the transition. See below for an example. 

The spreadsheet below has formulas already plugged in. You can use it to quickly and easily calculate your pet’s food for a transition!

How to transition your pet to a new diet

Step 6: Monitor your pet

The final and very important step when transitioning your pet to a new food is monitoring them closely during this time period. It is normal for pets to have some digestive upset during a transition, such as gas or softer stool. You can learn all about your pet’s feces at Assessing your pet’s poop.

Other less common (but very serious) changes that can happen are vomiting, weight loss, or refusal to eat. If any of these occur, stop feeding the new diet and call your pet’s normal veterinarian immediately.

You should also monitor your pet’s body condition during and after the transition. Even if you are feeding the same number of calories, the pet could respond differently to the new food and need adjustments. You should weigh your pet before and after the transition, and assess their body condition at these times as well. After the transition, it’s a good idea to continue this every two weeks until your pet is at a stable weight and body condition. 

Monitor feces during the transition