Iron deficiency anemia in suckling piglets: When physiology cannot keep up with breeding goals

Suckling piglets are the only neonates among mammals to show a disruption in the balance between iron supply and demand that results in spontaneous and progressive iron deficiency anemia (IDA). IDA in piglets exhibits a biphasic pathology with a mild manifestation just after birth due to critically low hepatic iron stores, which subsequently develops into severe anemia as a result of the extremely high growth rate in the early postnatal period produced by intensive selective breeding. Intriguingly, no cases of IDA have been reported in the offspring of wild boar, the major ancestor of contemporary pigs, still living in the wild in many regions of the world. Comparison of iron metabolism in the domestic pig and wild boar shows that the physiological mechanisms delivering iron for domestic piglets are similar to those established in wild boar offspring and thus are largely insufficient for their needs. Therefore, IDA in domestic pig neonates may be considered a man-made disorder whose symptoms manifest themselves in a particularly acute form in the offspring of modern breeds of domestic pig. Decades of breeding for economically important traits such as large litter size, high birthweight and rapid growth, has excessively increased iron demand. Effective prevention and treatment of IDA was introduced in the 1950s when iron-polysaccharide compounds suitable for parenteral administration were first employed extensively. However, anemic piglets remain an appropriate animal model of neonatal IDA for testing the effectiveness of new iron supplements and formulas, and for exploring and deciphering mechanisms of neonatal iron metabolism.