BCy Dr. David Jones, Ph.D., P.A.S.
Calcium is a macro mineral that has many functions for animals. Extracellular and intracellular calcium are important classifications with regard to the biological function of calcium. Extracellular calcium is involved with:
- formation of skeletal tissue
- transmission of nerve impulses
- skeletal and cardiac muscle contraction
- blood clotting
- component of milk
Intracellular calcium has the following functions:
- involved with enzyme activity
- a second messenger to convey information from the surface of a cell to the interior of a cell
Approximately, 98% of body calcium is contained within the bones, with phosphorus ions, to provide strength and hardness. The other 2% of body calcium can be found in the extracellular fluids. Calcium homeostasis must be maintained to prevent conditions such as hypocalcemia (milk fever).
Ruminants, pigs and chickens all require calcium in their diet. Dietary calcium requirements for different species are:
- lactating dairy cows: 0.7 to 1% of dietary dry matter
- dry cows/heifers: 0.5 to 1.0% of dietary dry matter
- growing steers: 0.45 to 0.8% of dietary dry matter
- pregnant beef heifers: 0.45 to 0.8% of dietary dry matter
- beef cow: 0.45 to 1.0% of dietary dry matter
- laying hens: 28 to 48 g/kg of dietary dry matter (average 4 g/d)
- non-lactating pigs: 18 to 19 g/d
- lactating sows: 50 to 55 g/d
A deficiency of calcium can be quite severe. Young animals will experience a lack of mineralization of new bone which will retard the growth of the animal (rickets). Older animals will develop osteoporosis or osteomalacia which can lead to spontaneous bone fractures.
During a year up to 30 times the total body calcium of a laying hen is put into the shells of eggs. A lack of calcium will lead to weak and brittle eggs. This leads to a reduction in egg yield and quality.
Transition dairy cows (21 days before calving to 21 days post calving) will run the risk of hypocalcemia (milk fever). Milk fever in dairy cows is due to a lack of free ionized calcium in the blood. The deficiency is caused by a lack of mobilization of calcium from the bones of the cow and absorption of calcium from the diet.
Anionic diets (may use anionic salts) are fed because they have a reduced pre-fresh cow index (PCI – developed by Agri-King) ranging from 450 to 550 depending on the location of the farm. Reducing the PCI adjusts the diet to provide an acidifying effect in the blood of the cow (urine pH between 6.0 and 7.2 can be used to determine desired results). Calcium carbonate will then be released from the bones to buffer (raise the pH) the blood. Calcium absorption from the diet (can supply 180 grams of calcium per day) is also increased. These combined processes will release free calcium that can be used by the cow to prevent milk fever.
Animals tend to handle elevated concentrations of dietary calcium quite well. However, problems can occur if calcium is over fed. Some of these issues are:
- reduced DMI and performance in dairy cows when dietary calcium is greater than 1% (research diets with 1.8% calcium have been fed without problems) -inhibition of trace mineral absorption (e.g. zinc)
- urinary calculi
- calcification of soft tissues
- an alkalizing effect that can lead to milk fever by counteracting the desired acidic effect from a low PCI diet
- calcium carbonate replaces needed protein and energy supplements in a ration (everything must add to 100%) causing lost performance
Some common sources of dietary calcium are:
- forages (legumes are higher in calcium than grasses; use Silo- King for improved digestibility and availability of forage calcium) - calcium carbonate
- meat and bone meal
- dicalcium phosphate
- monocalcium phosphate - calcium sulfate
- calcium chloride
- calcium propionate
Calcium is critical to livestock for proper physiological function. A deficiency in calcium can lead to serious performance issues that have a negative economic impact to producers. Agri-King rations are balanced to meet the calcium requirements of the intended species. The PCI system was developed by Agri-King to improve bone calcium mobilization to the blood and calcium absorption from the intestines which will properly maintain calcium balance of a pre-fresh dairy cow preventing milk fever. Forages are a good source of calcium and treating with Silo-King is an excellent way to improve forage quality making the forage calcium more available to the animals it is fed to. AK
