Dog Food Analytical Constituents Explained

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What are analytical constituents?

Every dog food sold in the UK must print an "analytical constituents" table on the packaging. This is a legal requirement under EU-derived feed regulations, and it tells you the guaranteed nutrient breakdown of the food.

The table typically lists four values: crude protein, crude fat, crude fibre, and crude ash. Some foods also declare moisture (especially wet foods) and additional nutrients like calcium or phosphorus.

These numbers look simple, but comparing them across different food types — wet vs dry, for example — requires understanding what they actually measure.

Crude protein

Crude protein is the total nitrogen content of the food, multiplied by a standard conversion factor. It represents all protein-based compounds, not just muscle meat.

What the number means:

• A dry food showing 26% crude protein means 26g of protein per 100g of kibble


• A wet food showing 8% crude protein means 8g of protein per 100g of food — but wet food is 75–80% water

Typical ranges:

• Dry dog food: 18–35% crude protein


• Wet dog food: 6–14% crude protein

The word "crude" does not mean low quality. It refers to the laboratory method used (Kjeldahl analysis), which measures total nitrogen rather than individual amino acids.

Crude fat

Crude fat measures the total extractable fat content. Fat is a concentrated energy source — roughly 2.25 times more calorie-dense than protein or carbohydrate per gram.

Typical ranges:

• Dry dog food: 8–20% crude fat


• Wet dog food: 3–8% crude fat

Higher fat is not automatically bad; working dogs or very active dogs may benefit from higher-fat formulations. But for a typical adult pet dog, moderate fat levels (10–15% in dry food) are common.

Crude fibre

Crude fibre represents the indigestible plant material in the food. It supports digestive regularity but is not a direct nutrient source.

Typical ranges:

• Dry dog food: 1.5–5% crude fibre


• Wet dog food: 0.3–1.5% crude fibre

Very high fibre (above 5% in dry food) may indicate heavy use of beet pulp, cellulose, or grain hulls as fillers. Very low fibre is common in high-meat formulations.

Crude ash

Ash is the most misunderstood number on the label. It does not mean literal ash is added to the food.

Crude ash is the mineral residue left after a sample is incinerated in a laboratory. It represents the total mineral content — calcium, phosphorus, magnesium, zinc, and other trace minerals combined.

Typical ranges:

• Dry dog food: 5–9% crude ash


• Wet dog food: 1.5–3% crude ash

Very high ash (above 10% in dry food) may indicate high bone meal content. Moderate ash levels are normal and expected.

Moisture

Moisture is not always declared on dry food (where it is typically 8–10%) but is always relevant for wet food (typically 75–82%).

This is the single biggest reason you cannot compare wet and dry food percentages at face value. A wet food with 10% protein and a dry food with 25% protein may actually provide similar protein levels per calorie.

How to compare: dry matter basis

To fairly compare two foods, convert to a dry matter basis:

1. Find the moisture content (or estimate: 8% for dry, 78% for wet)
2. Subtract moisture from 100 to get dry matter percentage
3. Divide each nutrient by the dry matter percentage

Example:

• Wet food: 10% protein, 78% moisture → dry matter = 22% → protein on dry matter = 10 ÷ 0.22 = 45.5%


• Dry food: 26% protein, 8% moisture → dry matter = 92% → protein on dry matter = 26 ÷ 0.92 = 28.3%

In this example, the wet food actually delivers more protein per unit of dry matter.

What analytical constituents do not tell you

These numbers have limits:

• Protein source: 26% crude protein could come from named chicken or from vague derivatives
• Digestibility: Two foods with the same protein percentage may differ greatly in how well a dog can absorb it
• Ingredient quality: The numbers describe quantity, not origin or quality
• Carbohydrate content: Not declared. You can estimate it: 100% minus protein, fat, fibre, ash, and moisture

How PetFoodFix uses these numbers

When you search for a dog food in the database, the analytical constituents are part of the label analysis. PetFoodFix cross-references these values against the ingredient list to identify transparency gaps — for example, a food claiming high protein but listing vague ingredients.

Want to see how this works in practice? View a sample report to see how label data is broken down into an educational score.

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