Extracellular calcium is essential for formation of skeletal tissues, transmission of nervous tissue impulses, excitation of skeletal and cardiac muscle contraction, blood clotting, and as a component of milk.
Intracellular calcium, while 1/10,000 of the concentration of extracellular calcium, is involved on the activity of a wide array of enzymes and serves as an important second messenger conveying information from the surface to the cell to the interior of the cell.
The calcium content of the blood plasma is homeostatically regulated within a relatively narrow range.
Injection of calcium often cause excessively high blood calcium for a period of time, probably by inhibiting the normal adjustments in the calcium regulatory mechanism which was the original cause of the milk fever.
When intake is inadequate cattle are able to withdraw calcium from the skeleton. However, over a long period, large amounts of calcium may be withdrawn, greatly weakening the bones.
Forges are generally satisfactory sources of calcium for grazing livestock, particularly when they contain leguminous species.
Calcium requirement for dairy cattle
