All pet foods contain 'ash' in their formulations. This is a term that needs to be explained, since some may think of ash in the context of fireplace residue and assume that fireplace ash has been added to perhaps bulk up the food. This, happily, is not the case.(I chanced upon this while trying to find out if cats can benefit from eating tripe, which is basically innards, like spleen/melts which they definitely can eat. Seems like tripe is primarily palatable only to dogs. Anyway, ash...)
Ash is not an additive in pet food. In fact, it is quite the reverse. Measuring existing ash content in a sample of pet food is a way of determining and describing the maximum mineral content of the food. The reason it is called ash is that, if you heat a sample of pet food to burn off all the organic components (which are combustible), you are left with the inorganic residue, which denotes the level of mineral in the sample, since minerals are the only inorganic (non-combustible) elements.
These minerals are primarily potassium and phosphorous, with smaller amounts of iron, calcium, magnesium, zinc and sodium, as well as trace amounts of many other minerals.
The ash content is important to know, not only to indicate the mineral content, but the quality of the protein present in the food. A high quality protein product will produce ash content generally no higher than 3%. While a small amount of mineral content is important to good nutrition, high quality protein content is essential. Look for this balance in the ingredients list.
To my layman understanding, I think the ash concept also relates to how much cat food ought to be 'cooked'; pedigree cat owners often feed raw meat to their felines before cat shows. There is of course an intricate balance to be maintained in how 'cooked' cat food should be - too cooked, you basically burn up the good stuff into 'ash'. Too raw, you are exposing your cat to bacteria that is typically present in raw meats, and even raw or semi-cooked eggs (FYI whole eggs should not be a daily diet as they interfere with the cat's vitamin B absorption). Palatability and the smell of their poo also may be affected with raw meats.
Raw meat however is definitely good for the cat to self-clean her teeth with. Cats who especially like to swallow their food whole without chewing (like Slinks) will be more likely to suffer from teeth and gum problems. Which is why I like to give them freeze-dried meat treats that they enjoy eating and will definitely chew.
Recently I have stopped cooking for my cats because Andy complains of the washing up he has to do after I cook. I have previously served my cats rare ground beef before but they are quite neutral towards it, not crazy like they are over their more preferred foods like fish. So I won't really know if raw meat diets will really make them healthier or not, since I am not a pedigree cat breeder. I guess we will just stick to the ash in our usual foods.
