Piglets are born with very little iron reserve. Colostrum and milk from the sow provide relatively little iron, perhaps only 15-50% of the daily requirement. Rapid growth and expansion of blood volume in suckling piglets ensures that a deficiency of iron and anemia will develop unless another source of iron is made available. This is especially the case in pigs raised in confinement without access to soil or feces containing iron. A small amount of copper is essential for utilization of iron. Copper deficiency can also lead to anemia that has many of the same clinical signs and lesions.
Signs and lesions of iron deficiency vary in piglets of different ages. Piglets not supplemented with iron will rapidly lose body condition and thrift after only about one week. At necropsy, these pigs will have pallor, a thin-walled heart, and edema of the lungs, muscles and connective tissues. In piglets that have received an insufficient supply of iron to successfully reach weaning at three to four weeks of age, rapid breathing and sudden deaths can occur. At necropsy there is marked enlargement of the heart and spleen, hydropericardium, ascites, edema in various tissues and fatty changes in the liver. Iron deficient piglets four to ten weeks of age will show similar signs and lesions. They are quite susceptible to bacterial infection and have little resistance to environmental chilling.
Diagnosis can often be made on the basis of a history that documents a lack of supplementation with iron; clinical signs and postmortem lesions will reinforce the diagnosis. Additionally, several laboratory procedures can be used to confirm the anemia. Among these is a study of stained blood smears that reveals a microcytic, hypochromic anemia. Hematology and serum chemistry will reveal reduced serum iron and transferrin saturation and a low hematocrit.
Prevention is possible by administration of supplemental iron (100-200mg). This can be done with water-soluble iron given per os or by parenteral injection of iron dextran. Parenteral administration is most commonly practiced and has the advantage of precise dosage. Iron dextran should only be injected into the neck muscles in order to prevent any possibility of staining valuable areas of the carcass. For the same reason, iron dextran should not be administered parenterally beyond seven days of age. Both forms of administration, when improperly used, can lead to iron toxicity and deaths.
Pigs deficient in vitamin E/selenium are highly susceptible to iron toxicity. Pigs raised outdoors with access to soil usually do not have an absolute requirement for iron supplementation but many producers still find it a beneficial practice even in these situations.