Calcium is a mineral of vital importance in the welfare of birds and consequently in their health and productive performance. In reality, birds are what their bones are.

Below we will review in a summarized way the absorption, the deposit, the release, its physiological effect and its excretion in birds.

(1) Calcium absorption in the gut of birds is influenced by:

• The presence, in the feed, of microminerals such as copper, fluorine, iron, magnesium, manganese, vanadium and zinc.
• The microbiota, through the escort enzymes of these microminerals, can act in a balanced way or cause relative deficiencies of any of them, even if they are present. Thus, the absorption of calcium in the intestine is affected by their presence and by the interrelationships with them.
• Vitamin D³ of endogenous or exogenous origin
• Botanical molecules that regulate the balance of the microbiota and other intestinal conditioner pronutrients molecules that improve the absorption of calcium in the intestine.

(2) Once calcium is absorbed, it is deposited in the bone, which in this way acts as a dynamic reservoir since it interacts with various elements of metabolism such as:

• Calcitonin that fixes calcium in bone
• Estrogens that mobilize calcium
• Hyperventilation that mobilizes calcium
• Parathyroid hormone that releases calcium
• Prostaglandins that release calcium

(3) Released calcium, in blood, is a multifunctional component of bird physiology through its influence on:

• Eggshell
• Blood coagulation
• Muscle contraction
• Acid base balance
• Bone structure
• Cellular permeability of liquids from the interior of the cells to the exterior and vice versa
• Immune system as a calcifier of organic lesions of infectious or parasitic origin and as a stimulant of the activity of t lymphocytes.
• Nerve impulse transmission

(4) Calcium excretion is regulated by the balance between the excretory action of estrogens and prostaglandins and the retention action of parathyroid hormone through:

• Oviduct
• Kidney

The complexity of calcium metabolism in the poultry body requires that the technical manager of poultry farms take into account the 19 parameters set out in this article, in order to maximize production parameters.