Iron

Iron is the central trace element contained in hemoglobin, myoglobin, and many enzyme systems essential for the horse’s organism to function normally. It plays a crucial role in oxygen transport and cellular respiration.

Sources

The iron supply in adult horses is generally ensured, as the usual horse feeds contain more iron than the horse requires on a daily basis. However, iron from some feedstuffs (cereal grains, cereal by-products, oilseed residues), in which it is predominantly present in the form of iron phytate, is poorly utilized. Iron absorption in the intestine also decreases with high manganese levels in the feed. 

Daily requirements

Adult horses (500kg body weight) have the following daily iron requirements:

Maintenance and Moderate work: 423 mg
Pregnant and Lactating Mares: 530 mg
Growing Foals: 400 mg

Deficiency

Iron is particularly essential for newborn foals, as their fetal iron reserves in the liver are used up relatively quickly after birth. Foals born prematurely in particular can have an iron deficiency, as around 50% of the total iron retained in the fetus is stored in the fetal liver in the last month of gestation. 
Often their iron requirements cannot be met by the mother's milk alone if neither mare nor foal are supported with iron-rich feed. Iron deficiency in foals manifests itself in anemia, poor performance, increased susceptibility to infections and impaired respiration. 

Excessive sweating combined with a low oral intake of iron can also lead to a deficiency situation in adult sport horses, which primarily manifests itself in a reduced willingness to perform and reduced stamina.

Excess

The maximum tolerable iron content in feed rations for adult horses is 1000 mg per kg dry matter. Iron absorption takes place via the entire gastrointestinal tract and is regulated by the protein hepcidin, which prevents excess iron absorption into the blood. High iron intake in the daily diet can lead to a decreased absorption of copper, manganese and zinc.

Especially foals react very sensitive to an iron overdose which can lead to diarrhoea, icterus (jaundice), dehydration, coma and death in very extreme cases, with pulmonary haemorrhage and liver degeneration.

Long-term high daily iron intake may lead in very rare cases to iron accumulation in the liver

Important to know

  • Iron utilization diminishes with higher intakes of cadmium, cobalt, copper, manganese and zinc
  • The iron supply can be assessed by means of a urine or blood test