Growth vs. adult diets: myths and truths

In this post, I thought we would consider some questions that people commonly have about diets formulated for growth, adult maintenance, and all life stages.

1) What is the difference between diets formulated for growth vs. adult maintenance? Are they really that different?

Yes, they actually are quite different. To explain how, I'll refer to AAFCO nutrient profiles, however FEDIAF recommendations are similar. Both AAFCO and FEDIAF profiles are derived from the National Research Council's (NRC) "Nutrient requirements of dogs and cats". In turn, the NRC guide is based on reputable scientific studies - it is, in essence, a big literature review.

The AAFCO Dog and Cat Food Nutrient Profiles were designed to establish practical minimum (and also some maximum) nutrient concentrations for commercial dog and cat foods, formulated from commonly used, non-purified, complex ingredients. The concentrations differ, in some instances, from minimum nutrient requirements traditionally developed by the NRC Committee on Animal Nutrition. This is because many of the NRC minimum nutrient requirements are based on research with purified diets and/or highly bioavailable nutrient sources that are not practical for use in commercial dog and cat foods.

There are two dog and two cat food nutrient profiles: Adult Maintenance and Growth and Reproduction. You can see a comparison of the dog food nutrient profiles here, on a caloric basis (sorry it's a bit blurry!):

What you can see is the following: diets for growing puppies are not just adult diets with a bit more protein, calcium and phosphorus. Requirements for other minerals, like iron and copper, are also different. Individual amino acid and fatty acid requirements are different. So growing animals do have different nutrient requirements to adults - this is an important thing to understand and remember.

2) Should I feed my large or giant breed pup an adult diet to "slow down growth" or prevent joint problems?

This is a common question, with a straightforward answer. Generally this advice is given with the hope of reducing excessive growth rates by providing a less energy-dense diet, with less calcium. However, this recommendation is not safe - think about the hundreds of adult maintenance diets that exist, and how varied their nutrient profiles are. These diets can exceed the established (NRC) safe upper limit for calcium, for puppies. Adult maintenance diets can also provide more kcal/gram and more calcium per kcal, when compared with growth diets formulated for large breed pups.

Additionally, as explained above, puppies require increased amounts of other minerals and fatty acids, when compared with adult dogs, and an adult maintenance diet may or may not provide these. Some economical diets for adult dogs may not provide enough protein for a growing pup.

3) Growth diets are higher in protein. Should I just feed my adult cat a kitten diet to provide them with more protein?

Whilst it is considered safe to feed a diet formulated for growth to adult cats, it's not something that we would generally recommend, for several reasons.

Firstly, diets formulated for growing kittens are often significantly higher in fat than diets formulated for adult cats. Since many adult cats have a problem with excess body weight, a lower fat diet is a better idea. Higher fat diets are more energy dense, which means your cat gets a smaller portion - most cats aren't thrilled about that idea!

Secondly, growth diets are substantially higher in phosphorus than adult maintenance - this is because kittens need more calcium and phosphorus during skeletal growth. However, once mature, it's likely not desirable to continue to feed a high phosphorus diet - research is ongoing, however there are some studies that indicate that feeding excess phosphorus (especially in the form of water-soluble supplements) may be damaging to the kidneys. Have a look at our previous blog post on cats and phosphorus if you would like some more information on this.

4) What's the story with "all life stages" diets? Is it a good idea to feed my dog or cat one?

As you have previously seen, AAFCO only recognises two nutrient profiles:

  1. Adult maintenance

  2. Growth and reproduction

However, products can be marketed as suitable for “all life stages” if they meet the requirements for both “Growth and reproduction” and “Adult maintenance”.

Really this just means that an all life stages diet meets the requirement for growth (although the magnesium requirement for adult maintenance is slightly higher than growth).

There's no evidence to suggest that feeding an all life stages diet to an adult dog might be harmful, however as you have just read above, we don't generally recommend all life stages diets for adult cats, as the phosphorus is often much higher, in order to meet the requirement for growth.

5) I have an Irish Wolfhound pup. Is there anything else I need to know about choosing an appropriate commercial diet?

Firstly, make sure you select a diet that specifies that it is appropriate for the growth of large-breed pups. From 2016 onwards, AAFCO guidelines require specific labelling for large and giant breed puppies (those whose adult weight is expected to exceed 70 pounds/31 kilograms).

AAFCO now requires dog foods formulated for growth and reproduction or all life stages to specify whether they include or exclude growth of large-breed dogs with one of the following statements:

[Pet Food Name] is formulated to meet the nutritional levels established by the AAFCO Dog Food Nutrient Profiles for growth/all life stages including growth of large-size dogs (70 lbs or more as an adu