Ash and its Importance in Pet Food


Ash is the inorganic material that remains after all organic material is burnt up. It is the final product during food combustion. What this means is that if you were to burn the product, all the protein, fat and carbohydrates would disappear and all that would remain is the minerals, or, the ash. It consists of the entire mineral content, such as calcium, magnesium, phosphorus, iron, zinc, sulfur, etc. Although it may not sound great, ash itself is important as it encompasses all necessary micro and macrominerals. It can come from natural sources, such as bone and shell, or as mineral additives to the food. Ash is not always listed on pet food labels and is not as informative as the actual content of the minerals themselves. However, we will discover in later modules the level of ash in the food is important when calculating carbohydrate content.


Historically, it has been the belief that ash levels were linked to urinary tract health in cats. Although this is not entirely untrue, researchers have been able to nail this down further and discover the main driver in crystal formation is the magnesium contained within the ash, not the ash itself. As we just learned, ash contains all the micro and macrominerals, magnesium being just one of the constituents of ash.

The ideal urinary pH of cats is about 6.0-6.7. The pH scale runs from 0-14, 0 being very acidic and 14 being very basic. A pH around 7 is considered to be neutral, like water. If a cat has urine above or below the ideal range, they are at risk of developing different types of crystals in their urine. This is a problem as these crystals are either passed, but this is very painful for the animal, or they must be removed surgically. In pet food, the issue is often that the pH becomes too high (basic), rather than too low (acidic). Therefore, most companies make a conscious effort to reduce the risk of crystals by adding key ingredients designed to neutralize the pH of cat urine.

Some of these methods include:

  1. Making recipes that are low in ash (<7%).

  2. Using ingredients that are low in magnesium so that the finished food contains less than 0.15% total magnesium content (<0.1% is ideal).

  3. Adding ingredients known to acidify and neutralize pH, such as the amino acid methionine, sodium bisulfate, and cranberries.

  4. Adding small quantities of salt. Salt promotes the cat to drink more water, thus forcing them to pass more urine.

  5. Formulate recipes that are lower in carbohydrates. New evidence suggests higher carbohydrate diets can promote crystal formation.

This is a small example of the technologies that exist to help combat crystal development in cats.  It is not guaranteed to prevent the development of urinary issues, as genetics, age, and sex can all have an influence.  Pet parents should always look for the inclusion of such ingredients to help protect from future issues.