Many new puppy owners are overwhelmed by the myriad food choices available. Chicken or beef? Whole grains or none? The questions multiply with every additional click of your laptop or step you take down the pet store aisle.

One of the most common questions concerns the differences between adult dog food and that which is designed for growing puppies. Many new owners wonder if they really need to purchase food marketed for puppies, or if they can get by with the standard foods marketed for adults.

The simple answer? You should feed puppy food to puppies and feed adult food to adult dogs. They are both designed with different goals in mind.

There’s certainly nothing toxic about adult dog food, and your puppy won’t become sick from eating the odd bowl of kibble or stealing morsels from his big-brother’s dish (aside, potentially, from some minor digestive upset). However, long-term damage can result from a steady diet of adult dog food.

Adult dog food is formulated much differently than puppy food, and these differences are important for the long-term health of your pet.

Differences Between Puppies and Adult Dogs

The entire reason that puppies and adults have differing nutritional needs is because they have important biological differences. They work differently, so they need different types of fuel.

For example, because of their small size, puppies have a higher surface-to-volume ratio than adult dogs do. This means that they lose body heat more quickly than adult dogs do. Puppies have to work harder to maintain their body temperature than larger, adult dogs do (although the same is true of small breeds vs. large breeds). This is also why puppies and small breeds tend to adore heated dog beds.

“Working harder” essentially means burning more calories in their internal furnaces, to offset the body heat that they continually radiate into the environment. This means puppies need more calories per pound of body weight than non-pregnant, non-lactating adults do.

Additionally, puppies grow rapidly; dogs complete the bulk of their growth in the first two or three years of life. This growth requires different resources than simply living does. Specifically, it means that puppies require more amino acids – the building blocks of proteins, and therefore tissues – than adults do.

Differences Between Puppy Food vs Adult Dog Food

As you’d expect, the differences between the biology of puppies and that of adults manifest as different nutritional requirements.

Perhaps not surprisingly, puppies and lactating mothers both have relatively similar nutritional needs. This has led the Association of American Feed Control Officials (AAFCO) – the primary regulatory body for dog food – to develop two different categories for food: “adult maintenance” versus “growth and reproduction.” We’ll call them adult and puppy for short – just know that dog food fur puppies is also good for lactating dogs.

The biggest primary difference between puppy food (growth and reproduction recipes) and adult (maintenance) food relates to protein. Puppy food should derive 22.5% of their calories from protein sources, while adult foods need only 18% of their calories from protein.

Adults can certainly tolerate the higher protein levels of puppy food, but it may lead to weight gain, due to the higher amount of protein calories.

However, puppies will often suffer from developmental problems if fed an adult food and deprived of the proteins they require.

Remember: “protein” really refers to a soup of different amino acids. Because not all amino acids are created equally, the AAFCO recommends differing amino acid compositions for adult and puppy dog foods.

Some of the starkest contrasts of amino acid compositions include:

• Argine
• Histidine
• Isoleucine
• Leucine
• Phenylalanine
• Ohenylalaline-tyrosine
• Thereorine

The AAFCO requires nearly 2x the amount of each of these amino acids in puppy foods than it does in adult dog foods. That is because these amino acids are intrinsic to the growth process.

The AAFCO also requires puppy foods to contain a bit more fat than adult foods do. Per the guidelines, adult food need only derive 5.5% of their calories from fat, while puppy food must derive 8.5% of their calories from fat. This is primarily to ensure that puppy foods are “energy dense.”

Fats contain more calories per pound than either proteins or carbohydrates do, which ensures that puppy food is packed with energy for stoking their internal fires.

Adult maintenance formulations, by contrast, are designed to be leaner, so they contain less fat, and therefore fewer calories in every bite.

The mineral content of puppy foods also differs from those of adult dog foods. For example, per AAFCO guidelines, puppy foods must be 1% calcium, while adult foods need only be 0.6% calcium. Similarly, puppy foods must be 0.8% phosphorus, while most adult dog foods are only 0.5% phosphorus.

What about Foods for “All Life Stages?” Are They Safe for Puppies?

In addition to foods that are labelled as being appropriate for “growth and reproduction” or “adult maintenance,” you may also see foods bearing a label that indicates they are appropriate for “all life stages.”

These foods are appropriate for most healthy dogs (they may not be good for some senior canines), so you can go ahead and feed them to your puppy.

These foods are designed to meet the requirements for “growth and reproduction” and “adult maintenance.” But because the nutritional requirements for puppy foods exceed those of typical adult foods, it means these are essentially puppy food.

Because they have higher protein and fat content than many adult foods, you will want to keep an eye on the body weight of adult dogs fed such recipes.

But as long as your pooch stays nice and svelte, they’re fine for adults too. This extra protein also makes puppy food or “all life stages” food a great dog food for weight gain if you’re trying to get a thin dog to a healthier weight.

Transitioning Your Puppy to Adult Dog Food

As your puppy ages, the difference in her nutritional needs will change. She’ll need fewer of the resources in her food to contribute to growth, but she’ll need more to support maintenance. As a result, you’ll need to switch her to a new dog food for adults as she completes these changes.

When to Transition to Adult Food

Consult with your vet to help determine the best time to change from puppy food to big-girl food, but most dogs are ready to change foods between 18 and 24 months of age. The exact age at which your “puppy” becomes a “dog” varies from one individual to the next, but most small breeds mature at relatively young ages, while most giant breeds require 2 years or more to fully mature.

Make the Change Gradually

Regardless of your pup’s age at the time of the food transition, it is important to make said transition gradually.

Start by mixing in a little adult dog food with your pup’s typical puppy food diet. About 10% – 20% is of the new food is ideal. If your pup tolerates that well (translation: no intestinal disturbances), you can double the amount of new food the next day. Always try to minimize intestinal distress, and don’t be afraid to slow down the transition if necessary.

It should usually take about a week or so to make the full transition from 100% puppy food to 100% adult food.

Things to Look for in Foods for Dogs (Regardless of Age)

While puppy foods and dog foods differ in their precise nutritional requirements, there are a number of characteristics that you should look for in any food that you offer your precious family member. Some of the most important traits of good foods include:

• Good foods feature a protein as the primary protein source. Dogs and puppies of all ages are best supported by a meat-based diet, so look for things like deboned chicken, duck, beef, pork or salmon as the first listed ingredient.
• Good foods don’t include unnecessary additives, including dyes or flavors. Artificial colors and other additives do not add anything important to your puppy’s diet, and they may trigger food allergies. Fortunately, most high-quality puppy foods now leave these types of ingredients out of their recipes.
• The very best foods are made in a country with high food-safety protocols. Countries like the United States, Canada, Australia, New Zealand and those of Western Europe typically have sufficient regulations in place to help ensure your puppy’s food does not contain any harmful ingredients, while those made in other countries often lack such regulations.
• Good foods may include by-products and meat-meals, but they must be specifically identified. By-products and meat-meals sound thoroughly disgusting to most people, but they often represent a viable and perfectly acceptable ingredient for your pup’s food; but they must be identified by species so that you know what your dog is getting.

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As you can see, it is important to give your puppy a food that is designed for her needs, but it’s also OK to offer your dog a meal or two of adult dog food if you are in a bind. Although any new food can upset her tummy, a small amount of adult food shouldn’t make her sick.

Have you ever found it necessary to feed your puppy some adult food? How did she handle it? Let us know about your experiences in the comments below.