Immune functions were studied in male calves fed milk replacer (MR) co
ntaining 10 or 50 mg iron (Fe)/kg. Calves fed 10 mg Fe/kg MR developed
marked hypoferremia and anemia, whereas serum-Fe and haemoglobin conc
entration of calves fed 50 mg Fe/kg MR were normal. Growth performance
was reduced, while feed/gain ratio, incidence of infections (especial
ly pneumonias), febrile body temperatures and antibiotic treatments we
re higher in calves fed 10 than 50 mg Fe/kg MR (p<0.05). Whereas antib
ody production (to horse erythrocytes) and lymphocyte stimulation (by
mitogens) were not significantly altered, cell-mediated immunity (meas
ured as cutaneous delayed-type hypersensitivity reaction to dinitroflu
oro-benzene), number of neutrophils with phagocytic capacity, activity
of the Fe-containing enzyme myeloperoxidase, blood serum IgG concentr
ation and the number and diameter of germinal centres as a measure of
the number and production of B-cells in cervical superficial lymphnode
s in calves fed 10 mg Fe/kg MR were reduced when compared with calves
fed 50 mg Fe/kg MR (p<0.05). In conclusion, severe Fe deficiency cause
d reduced growth performance, associated with and partly due to higher
incidence of infections because of defective immune reactions.