Calcium, also known as lime, is an earth alkali mineral that plays a vital role in animal health and metabolism.

Calcium in animals

More than 95% of all calcium (Ca) in the body is stored in the bones.

In both bones and milk, calcium occurs as calcium phosphate (Ca₃(PO₄)₂).

Therefore, both calcium and phosphorus (P) are required for bone formation and milk production.

The ratio of calcium to phosphorus in the ration is crucial. In recent years, there has been more focus on optimising or minimising phosphorus levels in feed formulations.

Dairy cows require large amounts of calcium to produce milk. The bones act as a calcium buffer. Vitamin D, in coordination with hormones, regulates calcium absorption and mobilisation between the intestines, blood and bones. As animals age, their ability to mobilise calcium decreases, increasing the risk of milk fever.

Besides its structural role, calcium is also essential for:

• Transmission of nerve impulses and muscle contraction
• Hormone production
• Blood clotting
• Regulation of blood pH
• Fertility
• Membrane activity regulation

Calcium requirements

Calcium requirements (CVB, 2016)

Calcium deficiency

A calcium deficiency can structurally lead to osteoporosis and leg problems. It also increases the risk of milk fever and muscle cramps can also occur. A high magnesium content, through mutual competition, lowers calcium absorption and can thus cause an indirect calcium deficiency. In the diet of dry cows, higher magnesium levels are used to stimulate calcium absorption.

Calcium surplus

Calcium excess is rare because the body has several mechanisms at its disposal to excrete excess calcium. A temporary excess calcium level has no consequences. A prolonged elevated calcium intake through feed can cause kidney problems and lead to the calcification of soft tissues, such as the kidneys, liver and vessel walls. The CVB (2005) gives a toxicity limit of 15g of calcium per kilogram of dry matter (for chronically high levels).

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