Developmental changes in serum ferritin concentration of dairy calves

Serum ferritin concentration of nursing calves was measured by a two-site immunoradiometric assay to assess developmental changes and to evaluate relationships of serum ferritin with iron-related blood characteristics. Serum ferritin concentration of calves was low at birth and elevated slightly at 3 days of age. From 1 wk of age onward, serum ferritin concentration of untreated calves and calves fed only whole milk for 4 wk decreased and remained low throughout the nursing period. This finding almost coincided with hematological characteristics. However, that nearly normal hematological measures and weight gain persisted and that they did not develop any anemic symptom indicate that serum ferritin concentration is more sensitive than other hematological characteristics to iron depletion. However, serum ferritin concentration of calves administered 130 mg of ferrous fumarate (40 mg iron) daily from 3 to 22 days of age or injected with 4 ml of iron-dextran intramuscularly (400 mg iron) at 3 days and 2 wk of age increased sharply just after treatment and persisted high for 2 to 6 wk of age. However, there was large variation between animals for serum ferritin concentration. Thus, it seems likely that serum ferritin concentration is an index for monitoring prelatent iron deficiency of calves.