Crude ash

Key points

"Crude ash" sounds alarming, but it is simply a measure of the total mineral content in food. The name comes from the measurement method: a sample is burned at a high temperature, and what remains after burning off the organic parts is the inorganic residue — that is, the minerals. Their mass is called ash [1].

Ash is neither an additive nor a filler

This is a common misconception: ash is not any kind of additive sprinkled into food, nor "dirt" or a filler. Nobody adds ash to food. It is solely the result of a measurement telling how many minerals are in the diet — such as calcium, phosphorus, potassium, sodium, magnesium or trace elements [1] [2].

High ash in BARF usually means "a lot of bone"

In a raw diet, the main source of minerals is bone and meaty bone. That is why high ash most often means a high share of bone in the diet [2]. This is a helpful clue: if ash is very high, it is worth checking whether there is too much bone (which boosts calcium and phosphorus and can stiffen the stool). Low ash on a boneless diet, in turn, signals that a source of calcium needs to be taken care of.

What to remember

Crude ash is a thermometer of mineral content, not an ingredient to avoid. In itself it is neither good nor bad — it is interpreted together with specific minerals, above all calcium and phosphorus and their Ca:P ratio.

Sources

1. Merck Veterinary Manual. Nutritional Requirements of Small Animals. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals
2. Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ (2010). Small Animal Clinical Nutrition, 5th Edition. https://www.markmorrisinstitute.org/sacn5.html