The aim of this study was to evaluate the dietary iron intake of 15-year-old adolescents from two different regions of Sweden, in relation to their iron status. The study comprised 185 boys and 209 girls, randomly selected from the official population register. The iron intake was calculated from a 7-day record, and varied between 7 and 35 and 6 and 27 mg per day for boys and girls, respectively. The daily median intakes in boys and girls were 18.7 and 14.2 mg, respectively. S-ferritin, s-iron, and s-transferrin saturation, measured in all the subjects, did not differ significantly between the two regions. However, the mean serum ferritin concentration was significantly higher in the boys (36.4 micrograms l-1) than in the girls (29.4 micrograms l-1) (p < 0.001). Low s-ferritin levels, defined as s-ferritin < 12 micrograms l-1 were found in seven boys (3.7%) and in 29 girls (13.9%). None of the adolescents had iron deficiency anaemia, defined as Hb < 110 gl-1 in combination with s-ferritin < 12 micrograms l-1. Regression and correlation analyses did not show any significant correlation between dietary iron intake and s-ferritin, or between s-ferritin and haemoglobin (Hb), MCH and MCHC. A significant correlation was found, however, between s-ferritin and transferrin saturation (p < 0.005) in both sexes. When the adolescents who still had s-ferritin < 12 micrograms l-1 at a second blood examination were given a 6 weeks trial with oral iron therapy, all of them showed an increase both in s-ferritin and in blood Hb. The 95% confidence intervals of s-ferritin for 15-year-old Swedish boys and girls were defined as 11-90 and 7-85 micrograms l-1, respectively.

Serum ferritin and serum transferrin receptor concentrations, growth and food habits were studied in healthy Swedish boys (n= 103) and girls (n= 124) at the age of 17 y and compared with those in the same adolescents at age 15. Between these ages, serum transferrin receptor increased significantly in both boys and girls. Serum ferritin increased significantly in boys but not in girls. The transferrin receptor/ferritin ratio increased significantly in girls but not in boys, indicating insufficient iron stores in the 17‐y‐old girls in relation to erythropoiesis and iron needs. Between 15 and 17 y the boys' frequency of consumption of milk and bread decreased, while they more often consumed pasta, cheese and coffee. The girls decreased their frequency intake of fat products, milk and meat. The frequency of meat consumption emerged as the single significant predictor for serum ferritin < 12μg/L in girls, but not in boys. The median daily iron intake, determined in a subsample, decreased in boys from 18.7 to 13.6mg and in girls from 14.1 to 8.8 mg, and the decrease was to a large extent due to cessation of iron fortification of flour. Conclusions: The results indicate insufficient iron stores in the 17‐y‐old girls in relation to erythropoiesis and iron needs, but more favourable iron stores in the boys. The absence of a significant decrease in mean serum ferritin despite rapid growth suggests that the earlier iron fortification of flour only marginally contributed to the iron status of Swedish adolescents of this age group.

Aim:As part of a longitudinal nutrition study of adolescents, changes in serum ferritin (s‐Ft), serum transferrin receptors (s‐TfR) and the TfR/Ft ratio from 15 to 21 y of age were studied in randomly selected Swedish adolescents. Methods:Blood samples from 60 males and 66 females were drawn at 15, 17 and 21 y of age. Results:In males, median s‐Ft increased significantly from 33 (μg 1 −1 at 15 y to 96 (μg 1−1 at 21 y, and in females, after a non‐significant decrease at 17 y, from 27 at 15 y to 34 (μg 1 at 21 y. Between 15 and 17 y, s‐TfR increased significantly, in males from 5.9 to 7.7 p.g 1, and in females from 5.2 to 7.6 μg 1−1, whereas s‐TfR decreased significantly in both genders between 17 and 21 y. The log (TfR/Ft) ratio did not change in males between 15 and 17 y, but decreased significantly from 2.2 ± 0.3 to 1.8 ±0.3 by the age of 21 y. In females, the TfR/Ft ratio increased significantly between 15 and 17 y, whereas a significant decrease was found by the age of 21 y. S‐Ft <12 μg 1−1 at 15, 17 and 21 y was 3, 2 and 2% in males, and in females 18, 26 and 21%, respectively. Conclusion:This study shows an increase in s‐Ft and a decline in s‐TfR in males, indicating increased iron stores. In females, s‐Ft did not increase significantly, whereas s‐TfR and the TfR/ Ft ratio decreased between 17 and 21 y, indicating that cellular iron needs were met.

We investigated the effect of an oral dose of 1, 2 or 4 soluble glass pellets containing cobalt, selenium and copper on the trace element and vitamin B12 status of sheep at pasture. Although the effective life of the pellet was intended to be 1 year, the retention of the pellet in the rumen was sometimes less than 6 months. Despite the apparently short retention period, an oral dose of 1 pellet was sufficient to provide physiologically significant quantities of copper, selenium and vitamin B12 to the animal for at least 45, 32 and 16 weeks respectively. The mean values for untreated sheep and sheep given 1 pellet were respectively 0.49 and 3.11 mmol copper/kg liver (dry matter) at week 45, 1.03 and 1.51 �mol selenium/L blood at week 32, and 1.15 and 1.82 nmol vitamin B12/L plasma at week 16. Sheep of normal copper and selenium status may be at risk of copper toxicity if given an oral dose of 2 or more pellets and of selenium toxicity if given 4 or more pellets at the same time. In sheep dosed with 4 pellets, mean liver copper and selenium concentrations exceeded, for 16 and 8 weeks respectively, the concentrations acceptable for human consumption.

The efficacy of 3 copper (Cu) supplements in maintaining adequate Cu status in Shorthorn heifers and Merino wethers was investigated in 3 experiments on alkaline peat soils in the South East of South Australia. The Cu supplements used were: soluble glass pellets containing Cu; copper oxide particles (CuO); Cu as a subcutaneous injection. Pasture contained moderate to high concentrations of molybdenum (Mo) (2.9-12.3 mg/kg), moderate Cu (3.8-8.7 mg/kg) and adequate sulfur (>1.7 g/kg) to limit the absorption of dietary Cu in ruminants. Shorthom heifers with normal Cu status were given 1 of 6 treatments (no Cu; 2 glass pellets; CuO at 3 doses; Cu injection) and introduced to the pasture (experiment 1). There was no liveweight response to any supplement. Relative to untreated heifers, mean liver Cu concentrations were raised only in heifers receiving the glass pellets or the highest dosage of CuO (20 g). The glass pellets maintained an adequate mean liver Cu concentration for at least 44 weeks but the CuO was effective for less than 24 weeks. Hypocupraemic heifers given 1 of 3 treatments (2 glass pellets; CuO; Cu injection) were significantly heavier (P<0.05) than the untreated heifers after 30 weeks (experiment 2). Mean plasma Cu concentrations were adequate at 30 weeks in the glass pellet and CuO groups, but mean liver concentrations indicated severe deficiency in all groups at 30 weeks. There was considerable individual variability in response to the glass pellet and CuO particle treatments, possibly due to the partial regurgitation of some of these orally dosed supplements. Merino wethers with adequate plasma and liver Cu concentrations received 1 of 5 treatments (no Cu; 1 glass pellet; 2 glass pellets; CuO; Cu injection) and were then grazed on a peat soil for a period of 1 year. Plasma Cu concentrations in the control group only indicated hypocupraemia at week 42. Liver Cu concentrations were higher (P<0.001) in all supplemented groups from week 18 to after week 30. Under the conditions of the experiments, 20 g CuO (the suggested dose) for the glass pellets or a single Cu injection were not sufficient to maintain the Cu status of heifers for 1 year. Repeat treatments or higher dose rates were required. The recommended dose rates of the supplements were adequate for wethers.