A Guide to Changing Dog Foods

Petfix Club
6th January 2021 - 4 min read

Some pet owners can be reluctant to change their dog’s diet because they are unsure of the effect that this may have on their pet. However sometimes we have to make a change, for the good of the dog, or to try a new range of food. People often wonder about the best way to make this transition.

How to Swap Dog Food

It is important that you introduce the new food gradually over four to five days, so you don’t finish one bag and suddenly start a new bag of different food. For a 4 day change over, follow this very simple 4 step process.

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On the first day you give 75% of the old food, and 25% of the new food.

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Second day, it’s 50% old food, 50% new food

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On the third day, it’s only 25% of the old food and 75% new food.

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On the fourth day, it’s 100% the new food.

Signs the Food is Successful

Short Term

  • The dog should enjoy eating it. When you produce food, your dog should often be excited, perhaps wagging their tail
  • There shouldn’t be any episodes of vomiting or diarrhea
  • You shouldn’t hear weird tummy sounds
  • No bad smells from flatulence/passing gas
  • Your pet should have a generally healthy digestive tract, with regular, well formed stools
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Long Term

Around 6-8 weeks after a dog is started on a diet, you should see the effect of the new nutrition on the pet’s body. When you’re used to looking at animals, you can see the difference between dogs that are on high-quality diets and those that are on poor quality diets. Healthy pets should have:

  • Shiny coat
  • Bright eyes
  • Well-defined muscles

Dogs on poor quality diets tend to have a duller coat, and sometimes there’s a bad, fusty, smell from their fur. They just don’t look as healthy.

The same general principles apply to cats, just in the same way.

If you are feeding a diet that your dog is obviously thriving on, then there’s no reason to change their diet. But if you feel that your pet is not absolutely thriving, as above, then it’s worth considering a new diet.

Effects of New Food

It generally takes approximately six weeks for the effects of new food to kick in. When you think about it, the food has to travel down from the mouth, into the stomach, then be absorbed in the intestines, go to the liver, be metabolised and circulate its way around into the lower level of cells in the skin. And then takes about another two to four weeks for those lower levels of skin cells to move up, to be the top levels of the skin. Only then will you notice the “shiny coat effect” of a high-quality diet on a dog.

How to choose the correct pet food

  • Ensure it is a high-quality product
  • Ensure it is a ‘complete’ diet (check the label). This labelling means that it must, by law, provide all of the nutrients a pet needs
  • Avoid products that contain the broad category of ‘animal derivatives’, as they tend to be lower quality, and less consistent than diets with specific named ingredients

Choosing High-quality VS Low-quality Foods

Pet food varies significantly, from one brand to another brand. As a general rule, dried kibble is the most popular way to feed dogs: it’s likely to be the most convenient, efficient, and best quality way to feed pets, in most cases.

High Quality Foods

High quality foods have more tightly defined ingredients, and so they vary less between different batches. If you analysed two batches of a high-quality brand of food, three to six months apart, they should be almost identical. As well as that, better quality foods tend to contain ingredients that are generally more digestible, leading to a much lower poo volume. So there’s less poo to pick up. And a lot of people really appreciate that.

Poor Quality Foods

If you choose one of the cheaper brands of pet food, and you did an analysis of two batches, maybe three or six months apart, you might find that the ingredients were entirely different. And what that means is that your pet may have a sudden change of ingredients as they go from one batch to another, making it more likely that they will suffer from a digestive upset.

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Reasons to Change to a new pet food

  • If your current food is not suitable (see above)
  • If you have access to an easier way of receiving the food, for example purchasing online instead of carrying a bag of food from the shops
  • Changing from a poor quality diet to a high-quality diet
  • Cost efficiency (but don’t sacrifice quality)
  • Your vet may advise a change of nutrition for the animal, e.g. changing from regular food to a science-based food that may help with an issue such as obesity or renal function

Changing Puppy Food

In general, in the first days of owning a puppy, you should stick to the food the breeder has been feeding the puppy on, assuming the puppy is doing well.

This is already a time of stress for a puppy, when it leaves its mother and goes to a new home. So, it makes sense to minimize the stress by at least keeping the diet the same for a short period of time.

So, ask the breeder for a small supply of the food that the puppy’s already been fed on, but once that supply runs out (that might be during the first week of life with you), you can change the food. You should choose a good quality food (based on the discussion above) or perhaps to a diet recommended by your vet.


If you need new puppy food or are considering changing to a high-quality, complete diet for your pet, why not try the Petfix Club range of dog food, carefully selected by Pete the vet and his team.