Protein on Dog and Cat Food Labels – What Those Numbers Actually Mean

Most pet parents feel good when they see a high protein percentage on the label.

“28% protein.”

“32% protein.”

“High protein.”

It sounds impressive, but the label is telling you far less than you think. That “crude protein” line is not measuring how much usable protein your dog or cat actually gets. It is measuring nitrogen in the food and converting it into a protein number with a formula that was designed over a hundred years ago.

If you want to understand what your pet is really eating, you need to know the difference between crude protein, digestible protein, and amino acid quality, and you need to understand how those numbers are generated, regulated, and sometimes used to mislead.

I'm going to try to break this down clearly.

1. Crude protein – what the label is actually showing you

On every complete pet food, you will see something like:

Crude protein (min) 24%

The keyword is crude. It does not mean “low quality.” It means the value comes from a specific lab method, not from counting actual protein molecules.

The standard method is the Kjeldahl or Dumas nitrogen test. A small sample of the food is digested in acid, all the nitrogen in the sample is measured, and then that nitrogen value is multiplied by a factor, usually 6.25, to get “crude protein.”

The logic: an average protein molecule contains about 16% nitrogen.

So:

% protein ≈ % nitrogen × (100 ÷ 16) ≈ % nitrogen × 6.25

This is how crude protein is calculated in:

• AAFCO-style pet food labels

• FSSAI nutrition labelling in India (general foods)

• BIS pet food standard IS 11968:2019, which refers to crude protein in specifications

The big catch:

The nitrogen test cannot tell whether the nitrogen comes from high quality meat protein, plant protein, collagen, or even non-protein nitrogen sources (NPN) like urea or melamine. All nitrogen gets counted as “protein.”

So crude protein = “nitrogen content × 6.25,” not “usable animal protein.”

2. Digestible protein – what the body actually gets

Your dog or cat does not digest labels. They digest amino acids.

Digestible protein = the portion of protein that is broken down, absorbed, and available to the body. This depends on:

• ingredient type (meat vs plant vs by-products)

• processing (gentle cooked vs extruded vs over-processed)

• fiber and anti-nutrients in the diet

• the species (cats often digest protein slightly better than dogs)

Studies comparing dogs and cats show that, on average, cats have higher protein digestibility than dogs for both wet and dry foods.  Typical commercial diets for dogs and cats show crude protein digestibilities in the 80–90% range when properly formulated; some refined protein ingredients have ileal digestibilities above 90%.

However, none of this is printed on the pack in a standardised way.

There are three reasons:

1. No simple test – true digestibility requires feeding trials or complex in vitro methods.

2. Regulators don’t require it – AAFCO, FDA, FSSAI and BIS all mandate crude protein guarantees, not digestible protein guarantees.

3. No harmonised regulatory definition – there is no legal standard for how a “digestible protein” number must be measured for labels, unlike the crude protein method which is tied to AOAC methods.

Some therapeutic or premium brands use phrases like “highly digestible protein,” but that is usually a claim, not a regulated digestible protein percentage with a fixed test behind it.

3. How digestibility is actually measured (and why it’s expensive)

To get real digestibility data, nutrition researchers and serious manufacturers use:

• In vivo feeding trials – dogs or cats are fed a diet for a set period, faeces are collected, and “apparent digestibility” is calculated from intake vs excretion.

• Ileal digestibility studies – even more precise; they measure amino acids at the end of the small intestine using markers or surgical techniques, so colonic fermentation doesn’t confuse the result.

• In vitro models – lab simulations of digestive enzymes and gut conditions to estimate digestibility from the ingredient composition.

These trials require:

• research facilities or contract labs

• specific ethics approvals

• specialised analytical equipment

• repeated runs for each new formula

  
  

For a small brand, a full digestibility trial can easily cost into the lakhs (or thousands of dollars) per diet, which is why most companies rely on existing literature and formulation software instead of testing every single product.

This is also why you almost never see “digestible protein: 22%” on a label. The infrastructure to support that as a regulatory number does not exist in pet food the way crude protein does.

4. Where do guideline numbers like “22.5% protein” come from?

When you see AAFCO or BIS minimum crude protein levels, those are based on nutrient requirement data with an assumption about digestibility.

For example, the AAFCO Dog Food Nutrient Profile for growth and reproduction sets a minimum crude protein of 22.5% on a dry matter basis. In the technical notes, they explain that this assumes a diet where about 18% digestible protein is needed and the protein sources are close to 100% digestible, giving an expected apparent digestibility of ~80%.

India’s BIS standard IS 11968:2019 for pet food sets crude protein ranges (often 18–35% depending on category) but, again, this is crude protein, not a digestible guarantee.

So when you see “meets AAFCO” or “complies with IS 11968,” understand that:

• the profile is based on crude protein measured via nitrogen

• digestibility is assumed, not stated

• the same crude protein number can hide very different digestible protein levels depending on the ingredients

5. Can a pack legally mention “digestible protein”?

Right now:

• US/AAFCO/FDA – labels must show crude protein in the guaranteed analysis. There is no standardised digestible protein line. Claims like “highly digestible” fall under general advertising and must not be misleading, but there is no single reference method brands must use.

• EU/FEDIAF – pet food labelling falls under feed legislation. Guarantees and terms are tightly regulated, and the core requirement is crude protein; digestibility may be referenced indirectly in certain “dietetic” feeds, but again, there is no routine digestible protein percentage on consumer labels.

• India (FSSAI + BIS) – pet food falls under general labelling guidelines plus IS 11968:2019. Protein is calculated as total Kjeldahl nitrogen × 6.25 as per FSSAI nutrition labelling rules, and the BIS pet food standard deals with crude protein guarantees. There is no dedicated digestible protein labelling requirement or format.

Could a company voluntarily add “estimated digestible protein 24%” based on its own internal trials? In theory yes, but:

• there is no harmonised test definition

• regulators could challenge the claim if it misleads consumers

• most companies avoid it because it complicates compliance in multiple markets

So in practice, what you see is crude protein only, with digestibility quietly hidden in marketing phrases and ingredient lists.

6. How is the protein percentage chosen for the label, and how accurate is it?

Manufacturers do lab tests on multiple batches, calculate an average crude protein value, and then choose a conservative minimum for the label. AAFCO’s own guidance shows an example where the batch average was about 24.8% crude protein as-fed, but the recommended label guarantee was set at 22% minimum, to allow for normal batch-to-batch variation.

Regulators expect actual values to be:

• at or above the guaranteed minimum for crude protein

• within a reasonable analytical variation range

There isn’t a single fixed “tolerance” published for all nutrients, but enforcement agencies usually compare several samples and check whether the product consistently meets or exceeds its claims based on AOAC reference methods.

For you as a parent, this means:

• the real crude protein content is often higher than the number on the pack

• two foods with “26% crude protein” can still differ significantly in true digestible protein, depending on ingredient quality and processing

7. Reading the protein line like a nutritionist

When you see “Crude protein (min) 26%” on a bag or tin:

You are looking at:

• nitrogen × 6.25

• measured by an AOAC method like Kjeldahl or Dumas

• guaranteed as a minimum, not exact amount

• not adjusted for digestibility

• not telling you amino acid profile

So to interpret that number better:

1. Convert it to dry matter if you are comparing wet and dry foods (because moisture dilutes the percentage). The FDA itself shows parents how to do this in their pet food education resources.

2. Look at ingredient sources of protein:

   
   

   • named meats, organs, eggs, fish

   • vs vague meals, plant concentrates, by-products

   
   

3. Understand that digestibility lives in the formulation and processing, not in the crude protein number. Research shows that well-chosen animal proteins and properly processed diets can reach >85–90% protein digestibility in both dogs and cats, while poorer ingredients and over-processing reduce it.

4. Remember that regulators in India, the US, and EU are all still using crude protein as the legal reference, so the science you care about will always be one step deeper than the label.

8. The takeaway

The protein number on a pet food label is not a lie, but it is incomplete. It is a chemically convenient way to estimate total nitrogen, multiplied into “crude protein,” and checked against AAFCO, FEDIAF, FSSAI, or BIS minimums. It tells you roughly how much nitrogen-based material is in the food, not how much clean, digestible animal protein your dog or cat will actually absorb.

If you want to choose better food, you cannot stop at “28%.” You need to understand where that protein comes from, how it was processed, and whether the brand cares enough to formulate for amino acid balance and digestibility rather than just hitting a crude number on paper.

References

• AAFCO. Feed Inspectors Manual and pet food labelling resources – crude protein defined as nitrogen × 6.25 using AOAC methods; guaranteed analysis requirements.

• AOAC 984.13 and related notes on Kjeldahl nitrogen for crude protein in animal feed and pet food.

• FDA. “Complete and Balanced Pet Food” – explanation of crude protein on dry matter vs as-fed basis and AAFCO protein minimums.

• Golder et al., 2020. “Cats Have Increased Protein Digestibility as Compared to Dogs” – differences in protein digestibility between species.

• Templeman et al., 2022 and related work on amino acid digestibility of novel proteins in dogs and cats.

• Song et al., 2023. In vitro equations for estimating ileal protein digestibility from crude protein and fibre in dog diets.

• BIS. IS 11968:2019 – Pet Food for Dogs and Cats – Specification; and associated summaries on crude protein ranges and testing expectations in India.

• FSSAI Compendium on Labelling and Nutrition – general rule that protein is listed as “Total Kjeldahl Nitrogen × 6.25.”