There is a very important myth to dispel regarding cat food, especially kibble, and that is that raw ash is bad for you and that the less a food has, the better. This is a belief rooted in many cat lovers, also due to the fact that the word “ash” evokes fireplace ash, or in any case something that is burnt and therefore bad to ingest.
In reality, in this article we will see in detail why raw ash is not bad for you, we will try to orient ourselves to understand how much there should be in a cat food, and we will see what raw ash is and why it is called that.
Fortunately, in recent years, also thanks to MicioGatto, information on industrial cat foods has increased considerably, clarifying colossal hoaxes and misunderstandings such as this one regarding raw ash, which has demonized it for a long time.
What is crude ash
The indication of the percentage of crude ash present in an industrial cat food is found on the label, where there is a list of ingredients, and the analytical composition, required by law:
This value is expressed as a percentage, like the other values of proteins, fats and fibers, which we also saw in the article dedicated to how to read cat food labels.
But while for proteins, fats and fibers we generally know what they are, and we are not afraid of them, for crude ash there is a bit of confusion and so let’s clarify what they are.
The crude ash present in an industrial cat food (and also for dogs) is nothing other than the minerals contained in that food, therefore calcium, phosphorus, magnesium, etc. Some feed companies, as you can see in the image above, in addition to the total percentage of crude ash, therefore of minerals present in the food, also indicate specifically how much of each mineral there is. In the case seen above there is 10.9% of crude ash, of which 2.7g/Kg are calcium, 1.6 g/Kg phosphorus and so on.
Minerals are essential for the life of animals, and also for ours, so they must be there and, as we will see in this article, it is not true that the lower the value of crude ash the better the food, because minerals are also good for cats.
But why are they called “ash” and not simply “minerals”? Simply because the law has decided so. The name crude ash comes from the process used to measure the quantity in an industrial food.
How is the crude ash of a food measured
The procedure for measuring how much crude ash is present in a cat food is this:
a 5g food sample is placed in an oven and burned at 550° for 3 hours
the sample is extracted and then put back in the oven for another 30 minutes
how much of the sample is left is measured and the percentage of the total is obtained
This procedure is regulated by REGULATION (EC) No. 152/2009 which establishes the sampling and analysis methods for official controls of animal feed, at point M
In practice, this procedure eliminates proteins, fats, fibres and water from the food, leaving only the mineral salts, which can then be measured. It does not indicate which minerals are present in the food, but only their quantity in percentage.
They are called “ash” precisely because the process is to burn the food sample at high temperatures, and what remains are ashes, which represent the minerals present in the sample.
But be careful, because some people get confused by saying that cat biscuits are cooked at more than 500° in the oven. This is wrong, because usually biscuits are cooked at temperatures from 80 to 200°, very often at 120°. At 500° they would carbonize and nothing would remain.
How much ash should there be in cat biscuits?
Measuring raw ash is mandatory not only for biscuits, but also for wet food and even for raw diets, because for all foods it is mandatory by law to indicate how many minerals are present. But the issue revolves mostly around kibble, perhaps because of the association that some people make with the fact that they are cooked at high temperatures, I don’t know, the fact is that it is always discussed when it comes to choosing which kibble to buy.
There are even those who choose a type of kibble just by reading how much crude ash it contains, and choose those that contain less. In reality, from some points of view, the opposite would be correct, that is, choosing foods that contain a high percentage of crude ash, let’s see why.
Generally, crude ash is more numerous in foods of animal origin than in those of vegetable origin. So the value of crude ash could be one of the many indicatorswhich helps us understand what type of protein is in the food we choose (meat protein or vegetable protein?)
Generally, vegetable foods contain 0.5 to 1.8% crude ash, fresh meat contains 2%, and dehydrated meat contains an average of 5%. In reality, if we look at the packages of kibble, the percentage of crude ash is always higher, this is because feed companies add calcium, phosphorus, and other minerals to the food, and rightly so, otherwise it would not be a complete food that satisfies all the nutritional needs of the cat.
Dr. Valerio Guiggi, in a very detailed article, in addition to explaining these concepts in great depth, also offers us a little trick to evaluate how “valid” a food is compared to the amount of crude ash present, more than anything to understand whether the raw materials used in that food are of high quality or poor quality.
The method, which is only valid for complete foods, is this: divide the percentage of proteins by the percentage of crude ash. An adequate result is between 4 and 5. If it is high, better, if low, probably the proteins used for that food are of poor quality, for example derived from beaks and feathers, or from plant foods.
Let’s do some real examples, which are useful for us to have another element to understand which foods are better than others, together with all the other parameters that we have seen in the other articles on cat nutrition, because here we really go into very specifics.
For example, Farmina N&D Prime Grain Free Adult Cat Chicken and Pomegranate has the following composition:
- Crude protein 44.0 %
- Crude fat 20.0 %
- Crude fiber 1.8 %
- Crude ash 8.5 %
If we do the calculation 44/8.5 = 5.17, which is a good value, as our nutrition expert teaches us.
Another example can be Smilla Adult Chicken Cat Food which has this analytical composition:
- Crude protein 32.0 %
- Crude fat 15.0 %
- Crude fiber 3.0 %
- Crude ash 6.5 %
And in this case the calculation will be 32/6.5 = 4.9, always a good value.
Of course, feed companies also know this calculation, and have already thought about how to get around it with raw materials that cost less than meat, for example by adding corn gluten, which increases the value of overall proteins, being rich in vegetable proteins, and leaves little ash.
How to evaluate a food based on crude ash?
The answer to this question is simply: you can’t. The calculations seen previously provide an indication that is too generic and vague. It is absurd to choose a food based only on how much crude ash it contains. It is better to look at the list of ingredients, the amount of protein and evaluate the many other aspects seen in numerous other articles.
Furthermore, the mineral requirement that each cat has is very variable, and it is not automatic to exclude foods rich in crude ash if a cat suffers from stones, for example. This is another cliché: the percentage of crude ash does not tell us anything about the type of mineral present in the food, and can be misleading.
In general, for a cat, more than the amount of raw ash, it is good to evaluate how much protein it consumes and how much water. It is always preferable to have a diet with more wet than dry and rich in proteins, and as we saw in the article on proteins, the more, in general, the better.
