What crude ash in pet food is and why it’s on the label
Food composition · · Farm Fresh
On every bag of kibble and every can, you’ll find one more line next to protein and fat: crude ash. It sounds as if someone had tipped ash from a stove into the food. Nothing of the kind happens. It’s the official name for the mineral content.
What crude ash means
Crude ash is what’s left of the food after it’s burned in a laboratory. A European regulation sets out the exact procedure: the sample is burned to ash at 550 °C and the residue is weighed. Proteins, fats and carbohydrates burn away, leaving minerals such as calcium, phosphorus, sodium, potassium and magnesium.
So no ash is added to the food. It isn’t an ingredient, which is why you won’t find it in the composition. It appears only among the analytical constituents, where the manufacturer may also call it “incinerated residue” or “inorganic matter”. Sometimes it’s just called ash.
Why it’s on the label
Because the law says so. The European regulation on feed labelling requires complete and complementary pet food for dogs and cats to state four analytical constituents: crude protein, crude fibre, crude fat and crude ash. So you’ll find crude ash on the label, whatever the food costs.
How much ash is usually in pet food
It depends on the ingredients and on how much water the food contains. For Farm Fresh food, the range looks like this:
| Food | Crude ash on the label |
|---|---|
| Dry food for dogs | 5–9.7% |
| Dry food for cats | 8–12% |
| Wet food for dogs | 2.4–3% |
| Wet food for cats | 1–4% |
| Fish oils | 0% |
| Treats | 3.6–16.2% |
Bones hold the most minerals. You can see this clearly in two cans of cat food with similar moisture. Cat Pure Beef, made of coarsely ground beef, has 1% ash. Cat Pure Poultry, which also contains softened poultry bones, has 4%.
How to compare kibble with a can
You can’t do it directly. The percentages on the label are calculated on the whole food, water included, and a can is roughly three-quarters water. So compare the ash in the dry matter, that is, in the food without its water:
ash in dry matter = crude ash ÷ (100 − moisture) × 100
| Food | Crude ash | Moisture | Ash in dry matter |
|---|---|---|---|
| Cat Adult Ocean Fish with Blueberries Grain Free, kibble | 12% | 10% | 13.3% |
| Cat Pure Salmon, can | 2.5% | 75% | 10% |
| Cat Pure Poultry, can | 4% | 77% | 17.4% |
On the label, the Cat Pure Poultry can has a third as much ash as this kibble, but in the dry matter it has more. Cat Pure cans are complementary pet food and the kibble is complete pet food, so the calculation compares only the ash, not the whole food.
Moisture only has to be on the label if it’s above 14%, so you often won’t find it on kibble. Where we do give it for our kibble, it’s 10%. You can use that figure for a rough comparison.
Is a higher or a lower number better?
Neither, in itself. Dogs and cats both need minerals, so the aim isn’t the lowest possible number. What’s more, crude ash doesn’t tell you which minerals the food contains or in what proportions. So look at the other lines too, if the manufacturer gives them. On Adult Beef, for example, you’ll find 1.95% calcium and 1.2% phosphorus alongside 8.9% crude ash.
If your pet is on a diet recommended by your vet, follow their advice when choosing food.
You’ll find the analysis of each recipe on its own page: dry food for dogs, dry food for cats, wet food for dogs and wet food for cats.