IMMUNE FUNCTIONS OF VEAL CALVES FED LOW AMOUNTS OF IRON

Immune functions were studied in male calves fed milk replacer (MR) containing 10 or 50 mg iron (Fe)/kg. Calves fed 10 mg Fe/kg MR developed marked hypoferremia and anemia, whereas serum-Fe and haemoglobin concentration of calves fed 50 mg Fe/kg MR were normal. Growth performance was reduced, while feed/gain ratio, incidence of infections (especially pneumonias), febrile body temperatures and antibiotic treatments were higher in calves fed 10 than 50 mg Fe/kg MR (p<0.05). Whereas antibody production (to horse erythrocytes) and lymphocyte stimulation (by mitogens) were not significantly altered, cell-mediated immunity (measured as cutaneous delayed-type hypersensitivity reaction to dinitrofluoro-benzene), number of neutrophils with phagocytic capacity, activity of the Fe-containing enzyme myeloperoxidase, blood serum IgG concentration and the number and diameter of germinal centres as a measure of the number and production of B-cells in cervical superficial lymphnodes 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 caused reduced growth performance, associated with and partly due to higher incidence of infections because of defective immune reactions.