What crude protein is and how to compare cans and dry food
Advice · · Topstein
On every can and every bag of dry food, the analytical constituents include a line for crude protein. The word “crude” says nothing about quality. It’s the official name of the figure for protein, which a laboratory doesn’t get by weighing the protein but by calculating it from nitrogen.
What crude protein means
A European regulation sets out the exact procedure: the nitrogen content of the food is measured and then converted to protein using a factor of 6.25. It’s an estimate of the protein content, not a direct weighing of the protein.
Why it’s on the label
Because the law says so. The European regulation on feed labelling requires compound feed for dogs and cats, meaning feed made from at least two feed materials, to state four analytical constituents: crude protein, crude fibre, crude fat, and crude ash. Mineral feed is the exception. For pet food, the manufacturer may also write just “protein”.
The percentages are calculated on the weight of the whole food, water included. That’s why the figures differ so much from one food to another.
How much crude protein Topstein food has
| Food | Crude protein on the label | Moisture |
|---|---|---|
| Cans | 13–18% | 66–75% |
| Stripes meat strips | 37.6–47.2% | 7–10.1% |
The strips look as if they had several times more protein. But they also have much less water.
How to compare a can with dry food
You can’t, not directly. A can is largely water; dry food isn’t. So compare protein in dry matter, that is, in the food without its water:
protein in dry matter = crude protein : (100 − moisture) × 100
| Food | Crude protein | Moisture | Protein in dry matter |
|---|---|---|---|
| Chicken in a Can, 800 g pack | 13% | 75% | 52% |
| Chicken in a Can, 400 g pack | 16% | 70% | 53.3% |
| Beef Stripes, strips | 45.3% | 7% | 48.7% |
| Fish Crunchies Small/Medium, dry food | 27% | 7% | 29% |
On the label, Beef Stripes have almost three times as much protein as Chicken in a Can 400 g, yet less in dry matter. And two packs of the same can differ by 3 percentage points on the label, but by only 1.3 in dry matter. Water makes the difference.
The dry food in the table is a complete feed, the can and the strips are complementary. So the calculation compares only the protein, not the food as a whole.
Moisture only has to be on the label when it exceeds 14%, so you often won’t find it on dry food. If that’s the case, ask the manufacturer.
Is a higher or a lower number better?
On its own, neither. Crude protein doesn’t reveal which ingredients the protein comes from: nitrogen is measured the same way in meat as in plants. So read the composition as well as the analytical constituents. For 16 of the 19 Topstein cans it says “100% animal protein”. The other three give percentages of meat, for example Meat in a Can – Beef: beef 50%, pork 35%, chicken 15%.
If your pet is on a diet recommended by your vet, follow their advice when choosing food.
You’ll find the analytical constituents of every recipe on its page: cans for dogs, cans for cats and treats for dogs.