Abstract
Ferritin, iron and total-iron binding capacities in blood serum of 20 Holstein steers of varying growth rates and grazing were measured. Sixteen steers averaging 200kg live weight (6-7 months of age) were divided equally in number into four weight gain groups (1.3, 0.8, 0.4 and 0.0kg). They were fed in confinement by four different feeding programs for 135 days. Four steers were grazed in pasture for 135 days, and their daily gain was 0.42kg. Serum ferritin concentration decreased slightly in steers of the 1.3kg daily gain group, but this protein concentration remained at a high level throughout the experimental period in steers of 0.0kg daily gain, although nutritional anemia did not appear. In contrast, serum ferritin concentration in the 0.8kg daily gain group remained constant at 15ng/ml. Serum ferritin concentration increased sharply in grazing steers with aging. On the other hand, total ironbinding capacity was clearly higher in animals of the 1.3kg daily gain group than that of other groups. Also, serum iron, counts of red blood cells, hemoglobin concentration and hematocrit value in cattle of the 1.3kg daily gain group were markedly high compared with those of other confinement groups. In grazing steers, erythrocytes increased in numbers and showed microcytic and normochromic change. Also, ferritin and non-heme iron concentration in the liver and spleen of cattle of the 1.3kg daily gain group were significantly lower than those of other confinement groups. Nonheme iron in the liver of grazing steers increased significantly after grazing. It was suggested that ferritin, iron, total iron-binding capacity and other hematological measurements in the blood of steers each reponded well to high caloric nutritional levels. However, changes in those values in undernutrition in this study were not clear. The elevation of body iron in grazing steers may be caused by a free intake of iron rich soil in pasture.
