Calcium in puppy nutrition
A lot has been said and written about calcium supplements in puppy food. As in everything, both excess and deficiency are harmful here. Calcium is necessary for the puppy to mineralize the growing skeleton: 99% of the calcium contained in the body is in the bone tissue. In an adult dog, the process of intestinal absorption of calcium has a dual character: passive distribution and active transfer. If the amount consumed increases, active absorption decreases and the adult, even receiving calcium-rich feed, absorbs no more than 10% of the calcium received. On the contrary, passive distribution plays a more important role in a puppy: it is not capable, as an adult, of clearly adapting absorption to the amount consumed, and the minimum absorption is always at least 40-50%. If there is not enough calcium in the feed, its absorption can be 95% of the diet.
HORMONAL REGULATION OF PHOSPHORUS-CALCIUM METABOLISM
The regulation of the exchange of calcium (Ca) and phosphorus (P) is subject to a very subtle mechanism, in the work of which 2 important hormones are involved:
– parathormone synthesized by the parathyroid glands, the main role of which is to increase the calcium content in the blood, which stimulates the release of calcium from the bone (osteolysis);
– calcitonin is a hormone synthesized by the thyroid gland, the role of which is, on the contrary, in the inhibition of osteolysis and in a decrease in the level of calcemia. Vitamin D, stimulating the absorption of calcium and phosphorus at the intestinal level, affects the growth and cellular differentiation of cartilage before mineralization of the latter and at the same time increases the intensity of changes in bone tissue.
The body responds to any change in the Ca / P ratio in the blood and, accordingly, regulates the release of hormones that seek to bring this ratio back to normal. The level of calcium in the blood (calcemia) is not a reliable indicator of excessive calcium intake, since the hormonal balance keeps it in a narrow framework, from 85 to 105 mg / l. Thus, with calcium intake, calcemia grows; as a result, the release of calcitonin immediately increases, which weakens the natural process of bone resorption and inhibits the increase in blood calcium.
CONSEQUENCES OF OVERCONSUMPTION OF CALCIUM
With constant excess calcium intake, the release of paratormone decreases and, as a result, the bone and cartilage tissue cease to change normally: the bones thicken and become denser. Cartilages whose maturation is delayed are subjected to unreasonably high mechanical stresses associated with physical activity and possible excess weight, which reduces their strength. Difficulty in changes in bone tissue and increasing fragility of cartilage can cause pain and serious musculoskeletal disorders: osteochondrosis, dissecting osteochondritis, compression of the spine … These disorders occur more easily and are more serious in fast-growing giant rocks. Excess calcium in the feed also makes it difficult to absorb other minerals and trace elements: phosphorus, magnesium, copper, zinc …
Thus, excess calcium can cause secondary deficiency in these elements.
The amount of calcium consumed depends on the caloric content of the feed and its calcium content. Since the diet is based primarily on the puppy’s energy needs, it would be most logical to establish a relationship between the calcium content and the energy value of the feed (and not the dry matter of the latter), which would be expressed in grams of calcium per 1000 kcal.
According to NRS 1985, the minimum requirement for calcium in relation to body weight is estimated at 320 mg / kg at the beginning of growth. Then it decreases and in an adult drops to 119 mg / kg. A diet containing at least 2.9 g of calcium per 1000 kcal will cover the needs of a growing puppy of any breed. For feed with an energy value of 3500 to 4000 kcal per 1 kg of dry matter, which is 1% of the calcium content in dry matter, or 0.9% of the calcium content in dry feed, the moisture content of which is close to 10%.
These values were determined in 1995 by the Association of American Feed Control Officials as the best recommendation for dog food manufacturers. This Association is the official food safety authority. Based on the latest research in this area, the Association has established the maximum allowable calcium content: 7.1 g / 1000 kcal or 2.5% calcium in the dry matter of the feed with an energy value of 3500 to 4000 kcal / kg of dry matter (AAFSO 1995 )
ADD CALCIUM. WHEN?
When a puppy is fed with a home diet (meat, rice, vegetables), the calcium content is clearly insufficient. In fact, regardless of the types of meat used, the mineral content is practically unchanged:
– from 7 to 10 mg of calcium per 100 g of dry matter, i.e. from about 0.01 to 0.03%;