Calcium in horses

What it does

Some 99 per cent of a horse's calcium is bound in the skeleton — roughly seven kilograms in an average-sized animal. What little circulates handles jobs that cannot wait: contracting muscle, carrying nerve signals, clotting blood. That circulating level is held steady at all times, and bone serves as the reserve it is drawn from.

Why it matters

A ration that supplies enough calcium month after month keeps the bone depot filled instead of drawing it down. That is the difference between a skeleton that carries reliably and one that quietly compensates for the feeding.

When it becomes critical

Calcium cannot be judged on its own. If the ration permanently provides little calcium or a lot of phosphorus, the ratio shifts at the expense of bone. The frame: at least as much calcium as phosphorus, at most three times as much. A moderate calcium surplus, by contrast, is uncritical.

How much a horse needs

Maintenance: about 12 g daily at 300 kg body weight up to around 20 g at 600 kg. Work barely changes this; the requirement is markedly higher for pregnant and lactating mares and during growth.

Cited values