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==What is Calcium?==

==What is Calcium?==

'''Calcium is the mineral that is found in the greatest abundance in mammals''', including dogs and cats, and also one of greatest importance because of its vital intracellular and extracellular functions as well as providing structural rigidity of the body. Most of the calcium in the body [99%] is found as calcium phosphate and stored in bones. A small, but vital portion is found in blood. Calcium in the blood [1% of total body calcium] exists in its free ionised form (iCa) [approximately 50%], protein bound [40-45%] and in a complexed or chelated state [5-10%].   

'''Calcium is the mineral that is found in the greatest abundance in mammals''', including dogs and cats, and also one of the greatest importance because of its vital intracellular and extracellular functions as well as providing structural rigidity of the body. Most of the calcium in the body [99%] is found as calcium phosphate and stored in [[Bones - Anatomy & Physiology|bones]]. A small, but vital portion is found in blood. Calcium in the blood [1% of total body calcium] exists in its free ionised form (iCa) [approximately 50%], protein bound [40-45%] and in a complexed or chelated state [5-10%].   

==Roles in the Body==

==Roles in the Body==

In terms of its structural role, the primary role of calcium is, when combined with [[Phosphorus - Nutrition|phosphorus]], in the formation of hard structures such as bones and teeth. Low dietary levels are therefore associated with '''severe skeletal problems'''. Calcium (especially in its ionised form) is also involved in numerous key intracellular and extracellular processes such as blood clotting, the transmission of nerve impulses, muscle contraction, maintenance of vasomotor tone, and cellular signalling. The level of calcium in the blood plasma is crucial to these functions and is under tight [[Calcium#Calcium Homeostasis|homeostatic control]]. Dietary calcium absorption is controlled by parathyroid hormone (PTH), which regulates the renal production of 1,25-dihydroxyvitamin D. This vitamin stimulates the absorption of calcium from the intestine, so by carefully controlling its production, calcium absorption can be regulated up at low intake and down at high intake. Nevertheless, Dobenecker<ref>Dobenecker, B. (2002). “Influence of calcium and phosphorus intake on the apparent digestibility of these minerals in growing dogs”. J Nutr. 132 (suppl):1665S-1667S.</ref> reported that beagle puppies younger than 4 to 5 months were unable to adjust the digestibility of calcium in relation to either excess or insufficient intakes. This makes it particularly important to adjust the supply of calcium in line with the dog’s requirements.

In terms of its structural role, the primary role of calcium is, when combined with [[Phosphorus - Nutrition|phosphorus]], in the formation of hard structures such as bones and teeth. Low dietary levels are therefore associated with '''severe skeletal problems'''. Calcium (especially in its ionised form) is also involved in numerous key intracellular and extracellular processes such as blood clotting, the transmission of nerve impulses, muscle contraction, maintenance of vasomotor tone, and cellular signalling. The level of calcium in the blood plasma is crucial to these functions and is under tight [[Calcium#Calcium Homeostasis|homeostatic control]]. Dietary calcium absorption is controlled by [[Calcium#Parathyroid Hormone|parathyroid hormone]] (PTH), which regulates the renal production of 1,25-dihydroxyvitamin D. This vitamin stimulates the absorption of calcium from the intestine, so by carefully controlling its production, calcium absorption can be regulated up at low intake and down at high intake. Nevertheless, Dobenecker<ref>Dobenecker, B. (2002). “Influence of calcium and phosphorus intake on the apparent digestibility of these minerals in growing dogs”. J Nutr. 132 (suppl):1665S-1667S.</ref> reported that beagle puppies younger than 4 to 5 months were unable to adjust the digestibility of calcium in relation to either excess or insufficient intakes. This makes it particularly important to adjust the supply of calcium in line with the dog’s requirements.

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[[File:Canine PTH.jpg|600px|center]]

[[File:Canine PTH.jpg|600px|center]]

[[Category:To Do - Nutrition]]

[[Category:To Do - Nutrition]]

[[Category:To Do - Nutrition GGP]]

[[Category:To Do - Nutrition preMars]]

[[Category:To Do - Nutrition Questions]]

[[Category:To Do - Nutrition Questions]]