Minerals are needed in trace amounts in the diet. They are provided by both plant and animal sources. Most of the minerals in cat food comes from bone and meat meals used in formulating the diets. Poor quality and cheap meat ingredients used in making cat food have a lot of bone in them. The bone is expensive to remove from the meat scraps, so it is just left in.
Most cat foods contain minerals in amounts that far exceed the requirements of the cat.
This is especially true of fish containing diets. These excessive minerals have to be eliminated from the cat's body, usually in the urine. Ash in cat food refers to the mineral residue that is left when a diet is burned to completion. The name does not specify which minerals or how much of any one there may be in the mix. Water Water is the most important of the six basic nutrients.