Much have been said and written about calcium additions to food of puppy. Here and everywhere both excess and lack are bad. Calcium is essential for mineralization of growing skeleton of puppy:
Osseous tissue contains 99 percent of all calcium in organism. The organism of adult dog assimilates calcium in two ways: passive distribution and active process. If the amount of calcium in digested food increases the active process slows down and even if it gets food rich in calcium the adult individual assimilates less than 10 percent of calcium available. In the puppy organism the passive distribution, on the contrary, plays the dominant role. Young organism is unable to adjust assimilation with consumption well like an adult individual and minimal assimilation is always less than 40-50 per cent. If there's lack of calcium in food, the assimilation may run up to 95 per cent of calcium available.
Hormonal regulation of phosphorus-calcium metabolism
Regulation of Calcium (Ca) and Phosphorus (P) metabolism is subdued to a very delicate mechanism, ruled by two important hormones:
- parathormone, synthesized by parathyroid glands. The main role of hormone is to increase Calcium content in blood and stimulate deliverance of Calcium out of bones (osteolysis);
- calcitonin, synthesized by thyroid gland. The role of this hormone is, on the contrary, to slow up the osteolysis and reduce the level of calcimia. D vitamin that stimulates assimilation of Calcium and Phosphorus on the enteric level, also influences the growth and differentiation of cells in cartilage until the latter is mineralized and at the same time increases the intensity of changes in osseous tissue.
Organism reacts at each change of Ca/P ratio in blood, which, correspondingly, regulates the secretion of hormones that tend to bring the ratio into a normal state. The level of Calcium content in blood (calcimia) is not a reliable index to show the excessive assimilation of Calcium, since balance of hormones limits it between 85 and 105 mg per liter. Thus, by a Calcium consumption the calcimia increases; this immediately results in secretion of calcitonin, which slows down the natural process of resorption of osseous tissue and prevents the increase of calcium content in blood.