Experimental study in rabbits

Halvorsen, K., and Halvorsen, S. (1973). Archives of Disease in Childhood, 48, 842. The 'early anaemia'; its relation to postnatal growth rate, milk feeding, and iron availability: experimental study in rabbits. In infants, the mechanism of the postnatal fall in haemoglobin to levels below those in adults, the 'early anaemia', is still unclear. In rabbits (as well as in other species) the 'early anaemia' develops during the suckling period, and Hb rapidly increases to adult levels after weaning. The fall in Hb and haematocrit is related to growth velocity. The rabbit has large stores of iron in the liver at birth, and even at the time of declining Hb concentration there are considerable amounts of stored iron still present. In spite of this, serum iron decreases and total iron-binding capacity increases towards the end of the suckling period. Parenteral iron given from the 10th day of life completely prevents the anaemia, and even leads to increases of haematocrit and red cell volume above the normal levels of adult rabbits. The 'early anaemia' in rabbits is thus iron responsive. An iron-deficient type of erythropoiesis, at a time when depot iron is present suggests that iron is not mobilized from iron stores in amount sufficient to maintain the very rapid erythropoiesis. Thus it is concluded that unavailability of iron rather than lack of iron stores is mainly responsible for the 'early anaemia'. The term 'physiological' applied to the 'early anaemia' may be misleading in some species because of lack of knowledge about the optimum supply of various essential nutrients for erythropoiesis. The same may also be true in premature infants who may be deficient in copper, folic acid, and vitamin E: in addition, unavailability of stored iron may contribute to the 'early anaemia'.