In the cat’s diet (and the diet of most animals) calcium needs to stand in a certain ratio to the mineral phosphorus, the later which occurs in abundance in meat. Presumably, the ideal ratio of calcium to phosphorus would be that of adult, wild mice (determined to be the primary natural food source of the cat) which is 1.33 parts of calcium to ever 1 part of phosphorus.
Calcium is the most abundant mineral in the body, and bone contains 99% of the body’s calcium. 70% of the calcium in bone consists as the calcium phosphate mineral Hydroxyapatite, which is also known as “bone mineral”. It gives bone its rigidity. Tooth enamel, for example, is almost 90% Hydroxyapatite or calcium phosphate. In addition to forming bone density, calcium serves vital functions in the body. For example, enzyme activity, contraction of muscles, release of neurotransmitters, regulation of heart beat, and the clotting of blood all depend on calcium. The calcium in bone serves as a reservoir to maintain blood calcium and enable these functions. If the diet does not provide enough calcium to replenish the mobile stores of calcium in the bone, deficiencies will occur.
Phosphorus is the second most abundant mineral in the body, and bone contains 85% of the body’s phosphorus. The rest is found in cells and tissue throughout the body, where it plays an essential role in how the body stores and uses energy, and regulates the growth, maintenance, and repair of all tissues and cell. It helps filter waste from the kidneys, and is essential for the production of the genetic building blocks, DNA and RNA. Phosphorus is also needed to help balance and use other vitamins and minerals, including vitamin D, iodine, magnesium, and zinc.
Like calcium, phosphorus is an important mineral in the soil and is essential for plant growth. Herbivores meet their own need for calcium and phosphorus by eating plants, and in turn supply carnivores with calcium and phosphorus with their bones and flesh.
How much dietary calcium is optimal for the cat depends not only on the minimal requirement to maintain blood calcium, but also on the amount of phosphorus supplied in the diet. Eating whole prey will not only meet the cat’s requirement for calcium, but also in an amount that is in a metabolically ideal ratio to phosphorus. An important aspect of formulating a diet for cats is, therefore, to replicate this ration of calcium to phosphorus. Too much phosphorus in the diet, disproportionate to calcium, will cause a calcium deficiency.
Phosphorus occurs most abundant in high protein animal tissue like meat, bones, milk, and eggs. In bones and milk, it is already found in a bond with calcium as the calcium phosphate Hydroxyapatite. In meat an eggs, however, it occurs as organophosphate without bond to calcium, and since meat provides the basis of a diet for cats, the phosphorus in meat (and to a lesser extent in eggs, because egg yolks makes for only a small portion of the diet) needs to be balanced with an additional source of calcium.
As discussed elsewhere (see: Freeze-dried bone) the best substitute for the natural source of calcium from bone, found in the cat’s natural prey diet, is natural bone. It has proved impossible, however, to balance phosphorus in pure meat (as it is used in the raw meat diet) with the addition of bone meal as a source of calcium, without grossly exceeding the total amount of calcium and phosphorus that would be supplied by the cat’s natural prey diet.
The reason for this is, that the total weight of a mouse, for example, is not made up entirely of pure flesh (meat) and bone alone. There is a great deal of other tissue like skin, hair, and entrails which add volume to the mouse and supply nutrients to the cat, but contain little phosphorus. These parts are not included in the raw meat diet, and the volume of the raw meat diet is almost entirely made up of pure meat, liver, and egg yolk, which are all high in phosphorus. It would take a disproportionate amount of bone (as bone meal or freeze-dried bone) to supply enough calcium to balance the amount of phosphorus supplied by these foods, because bone already contains phosphorus in a ration of 1 part phosphorus to every 2 parts of calcium.
Enough bone could be added to meat to create an overall ideal calcium to phosphorus, but the diet would contain much more total calcium and phosphorus than would be supplied by prey. As long as calcium and phosphorus stand in a correct ration to each other, this should not matter in a healthy individual. However, individuals with compromised kidney function will find it difficult to cope with the excess of phosphorus in the diet. Excessively high amounts of calcium can depress function of magnesium. It can also contribute to constipation and formation of oxalate stones.
To better mimic the natural levels of calcium and phosphorus as they are found in prey, and to prevent possible harmful effects from an over-abundance of calcium and phosphorus in the diet, Calcium Carbonate is added to the TCfeline premix as a pure source of calcium to eliminate the need to rely on calcium from bone alone.
The calcium carbonate used in TCfeline was laid down over 300 million years ago as a large graveyard of marine animals, similar to today’s oysters, which formed under very favorable conditions in a shallow marine environment. These marine animal remains, composed of calcium carbonate, were then cemented together with calcium carbonate precipitated out of the primordial sea. This deposit was then further purified and metamorphosed by various natural geological processes including high pressure caused by further deposition and high temperatures resulting from intrusions of hot magma. Over time, the deposit was them raised up and subsequent erosion has left it exposed and available as an extremely pure source of natural ground limestone in the Mojave Desert of California. The very low levels of led in this deposit make it a truly unique source for both food and dietary supplement application. The led determination of this calcium carbonate is in accordance with the California Attorney General Proposition 65 Testing Protocol method.