Evaluation of iron status in lemurs by analysis of serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation

OBJECTIVE: To assess serum iron and ferritin concentrations, total iron-binding capacity, and transferrin saturation as indicators of iron metabolic status in 3 genera of lemurs and determine whether these variables are useful for screening for iron overload. DESIGN: Cross-sectional study. ANIMALS: 11 ring-tailed lemurs (Lemur catta), 11 black lemurs (Eulemur macaco macaco), and 11 red-ruffed lemurs (Varecia rubra). PROCEDURES: Blood samples were collected weekly for 3 weeks and assayed for serum iron and ferritin concentrations and total iron-binding capacity. Liver biopsy specimens were evaluated histologically and assayed for total iron, nonheme iron, and trace mineral concentrations. Deposition of iron was scored on Prussian blue-stained slides. RESULTS: Hepatic iron content ranged from 497 to 12,800 Pg/g dry weight (median, 2,165 Pg/g). Differences were seen in mean hepatic iron content across genera, with ruffed lemurs having the highest concentrations and ring-tailed lemurs having the lowest. Iron accumulation in the liver was mild, and cellular pathologic changes associated with iron storage disease were not detected in any lemur. Ferritin concentration was the only variable that correlated significantly with hepatic iron content in all 3 genera of lemurs; however, both transferrin saturation and serum iron concentration were correlated with hepatic iron concentration in ring-tailed and ruffed lemurs. CONCLUSIONS AND CLINICAL RELEVANCE: Serum ferritin concentration was the only variable that was consistently correlated with hepatic iron content in all 3 genera. Mean hepatic iron content varied across genera, suggesting that the propensity for lemurs to develop iron overload in captivity may vary across taxa.     

Effect of dietary iron content on hematologic and other measures of iron adequacy in dogs

Eighteen 9- to 10-week old Beagles were fed casein-based diets (4,710 kcal of metabolizable energy/kg of body weight) containing either 12, 80, or 160 mg of iron/kg of diet. Growth and feed consumption were monitored throughout the 47-day study. Hematocrit (Hct), hemoglobin (Hb) concentration, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), RBC numbers, erythrocyte protoporphyrin (EP) concentration, serum iron concentration, serum total iron-binding capacity (TIBC), and serum ferritin concentration were determined weekly. Growth rate and feed efficiency were not significantly influenced by dietary iron content. At 14 days, Hb concentration, Hct, MCV, MCH, RBC numbers, and serum iron concentration were significantly (P less than 0.05) lower in dogs fed the 12 mg/kg diet, and remained significantly low for the remainder of the study. Erythrocyte protoporphyrin concentration increased significantly (P less than 0.05) by 14 days in dogs fed the basal diet, and remained significantly high relative to that in dogs of the other dietary groups for the remainder of the study. Serum ferritin concentration decreased in dogs of the group fed the basal diet, with a significant (P less than 0.05) difference beyond day 42. Differences in Hct, MCH, MCV, or hemoglobin, serum iron, serum ferritin, or EP concentration were not found between groups fed 80 and 160 mg of iron/kg of diet. Liver nonheme iron content was significantly (P less than 0.05) affected by dietary iron content.     

Serum ferritin, serum iron, and erythrocyte values in foals

Twenty-one healthy Thoroughbred and Quarter Horse foals were studied from birth until 1 year of age. Foals had access to an iron-supplemented creep feed before weaning and were fed an iron-supplemented concentrate as part of their diet after weaning at 4 months of age. Initial blood samples were taken before foals were allowed to nurse. Serum iron concentration, total iron-binding capacity, and PCV decreased during the foal's first 24 hours of life. Serum iron concentration decreased rapidly from 446 +/- 16 micrograms/dl (mean +/- SE) at birth to 105 +/- 11 micrograms/dl at 3 days of age. Serum ferritin concentration increased from a mean of 85 +/- 8 ng/ml at birth to 159 +/- 11 ng/ml at 1 day of age. Thereafter, ferritin concentration decreased gradually to a minimum of 61 +/- 6 ng/ml at 3 weeks of age, and then at 6 months increased to values similar to those from reference adult horses. The ferritin concentration in colostrum at birth was 354 +/- 42 ng/ml, compared with 25 +/- 2 ng/ml in milk 1 day later. The decrease and then increase in serum ferritin concentration occurred concomitantly with opposite changes in serum total iron-binding capacity. The mean PCV decreased gradually to a minimum at 3 months of age. This decrease was associated with an increasing number of microcytes, as determined with a cell-size distribution analyzer.     

Survey and clinical application of serum iron, total iron binding capacity, transferrin saturation, and serum ferritin in captive black and white ruffed lemurs (Varecia variegata variegata).

Serum samples from 63 clinically normal captive black and white ruffed lemurs (Varecia variegata variegata) were analyzed to survey serum iron, total iron binding capacity, transferrin saturation, and serum ferritin levels. Data analysis showed no differences in these analytes attributable to sex, but significantly higher levels of serum iron, transferrin saturation, and serum ferritin in older animals. The survey data were examined in light of two black and white ruffed lemurs that were treated for iron overload with serial phlebotomies. Prior to therapy, both phlebotomized lemurs had excess hepatic iron deposition, but had serum iron, transferrin saturation, and serum ferritin below the upper limits observed in the survey animals, suggesting that some clinically normal animals included in the survey may have accumulated excess systemic iron. Serial phlebotomy therapy reduced serum iron, transferrin saturation, and serum ferritin in both animals. Three years after the conclusion of therapy in the one remaining case, serum iron and transferrin saturation have risen substantially, whereas serum ferritin has risen slightly. Serum iron, transferrin saturation, and serum ferritin may be useful predictors of systemic iron stores in this species, though the correlation between these parameters and systemic iron stores needs to be determined.     

Exogenous corticosteroids increase serum iron concentrations in mature horses and ponies

Corticosteroid preparation was administered to 7 Shetland Ponies and 10 Quarter Horses. Serum iron concentration increased dramatically for 48 to 72 hours after the steroid treatment, whereas serum iron-binding capacity and serum ferritin concentration did not. An increase in available iron may allow bacteria to proliferate when ponies or horses are stressed or treated inappropriately with corticosteroids.     

Enzyme-linked immunosorbent assay to quantitate serum ferritin in black and white ruffed lemurs (Varecia variegata variegata).

Lemurs in captivity progressively accumulate iron deposits in a variety of organs (hemosiderosis) including duodenum, liver, and spleen throughout their lives. When excessive, the toxic effects of intracellular iron on parenchymal cells, particularly the liver, can result in clinical disease and death. The pathogenesis of excessive iron storage in these species has been attributed to dietary factors related to diets commonly fed in captivity. Tissue iron stores can be directly estimated by tissue biopsy and histologic examination, or quantitated by chemical analysis of biopsy tissue, However, expense and risk associated with anesthesia and surgery prevent routine use of tissue biopsy to assess iron status. A noninvasive means of assessing total body iron stores is needed to monitor iron stores in lemurs to determine whether dietary modification is preventing excessive iron deposition, and to monitor potential therapies such as phlebotomy or chelation. Serum ferritin concentration correlates with tissue iron stores in humans, horses, calves, dogs, cats, and pigs. Serum ferritin is considered the best serum analyte to predict total body iron stores in these species and is more reliable than serum iron or total iron binding capacity, both of which may be affected by disorders unrelated to iron adequacy or excess including hypoproteinemia, chronic infection, hemolytic anemia, hypothyroidism, renal disease, and drug administration. We have developed an enzyme-linked immunosorbent assay to measure serum ferritin in lemurs. The assay uses polyclonal rabbit anti-human ferritin antibodies in a sandwich arrangement. Ferritin isolated from liver and spleen of a black and white ruffed lemur (Varecia variegata variegata) was used as a standard. Ferritin standards were linear from 0 to 50 microg/L. Recovery of purified ferritin from lemur serum varied from 95% to 110%. The within-assay variability was 4.5%, and the assay-to-assay variability for three different samples ranged from 10% to 17%. The assay also measures serum ferritin in several other lemur species.     

Serum zinc, chromium, and iron concentrations in dogs with lymphoma and osteosarcoma

We compared serum concentrations of zinc, chromium, and iron in dogs with cancer to those of normal dogs. Dogs with lymphoma (n = 50) and osteosarcoma (n = 52) were evaluated. Dogs with lymphoma had significantly lower (P = .0028) mean serum zinc concentrations (mean +/- SD; 1.0 +/- 0.3 mg/L) when compared to normal dogs (1.2 +/- 0.4 mg/L). Dogs with osteosarcoma also had lower mean serum zinc concentrations (1.1 +/- 0.4 mg/L), but this difference was not significant (P = .075). Serum chromium concentrations were significantly lower in dogs with lymphoma (2.6 +/- 2.6 microg/L, P = .0007) and osteosarcoma (2.4 +/- 3.1 microg/L, P = .0001) compared to normal dogs (4.7 +/- 2.8 microg/L). Serum iron concentrations and total iron-binding capacity were significantly lower in dogs with lymphoma (110.8 +/- 56.7 microg/dL, P < .0001, and 236.6 +/- 45.6 microg/dL, P < .0001, respectively) and osteosarcoma (99.6 +/- 49.3 microg/dL, P < .0001, and 245.0 +/- 43.8 microg/dL, P = .0011, respectively) when compared to normal dogs (175.1 +/- 56.7 microg/dL and 277.1 +/- 47.4 microg/dL). Mean ferritin concentration was significantly higher in dogs with lymphoma (1291.7 +/- 63.0 microg/L) than in normal dogs (805.8 +/- 291.1 microg/L, P < .0001) and dogs with osteosarcoma (826.5 +/- 309.2 microg/L, P < .0001). Further investigation is needed to explore the clinical significance of these mineral abnormalities in dogs with cancer.     

Potential effects of glucocorticoids on serum iron concentration in dogs

Prednisone was give norally(2mg/kg b.i.d.) to seven healthy mixed breed dogs for 3 consecutive days. Serum iron concentration increased significantly (p < 0.05) from 142 +/- 26 micro g/dl (mean +/- SE) before a drug adminis- tration on Day 0 to a maximum of 307 +/- 47 micro g/dl on Day 2, and returned to the Day 0 value by Day 5. Mean total iron binding capacity did not vary more than 25% from the Day 0 value during the 9 day long study. The percent saturation of transferrin with iron increased from 33 +/- 6% on Day 0 to a maximum of 71 +/- 9% on Day 3. This determination had decreased to 34 +/- 3% on Day 5. No statistically significant changes occurred in these parameters studied in six control dogs that were not given the drug. To determine whether serum iron concentration might be correlated with endogenous serum cortisol concentration, these tests were determined in serum collected from nine dogs at 7 a.m., 3 p.m., and 11 p.m. each day for 3 consecutive days. Serum iron concentration was lower at 7 a.m. (147 +/- 9 micro g/dl) than at 3 p.m. (164 +/- 9 micro g/dl) or 11 p.m. (159 +/- 10 micro g/dl). Likewise serum cortisol was lower at 7 a.m. (1.29 +/- 0.18 micro g/dl) than at 3 p.m. (1.49 +/- 0.19 micro g/dl) or 11 p.m. (1.51 +/- 0.22 micro g/dl). There was a significant positive linear correlation between serum iron and serum cortisol concentrations when they were compared using mean values for each dog. From these studies, it appears that exogenously administered glucocorticoids and endogenous increases in serum cortisol concentrations may result in increased serum iron concentrations in dogs.     

Iron storage disease in captive Egyptian fruit bats (Rousettus aegyptiacus): relationship of blood iron parameters to hepatic iron concentrations and hepatic histopathology.

This study evaluated the relationship between blood iron parameters and hepatic iron concentrations, and correlation of histologic findings with hepatic iron concentrations in a captive population of Egyptian fruit bats (Rousettus aegyptiacus) and island flying foxes (Pteropus hypomelanus). Blood samples were collected for complete blood counts, plasma biochemical profiles, serum iron concentrations, total iron-binding capacity, whole-blood lead concentrations, and plasma ferritin assays. Liver samples obtained by laparotomy were divided, with one half processed for histologic examination and the other half frozen and submitted for tissue mineral analysis. The histologic sections were scored by two blinded observers for iron deposition, necrosis, and fibrosis. The Egyptian fruit bats had significantly higher liver iron (mean = 3,669 +/- 1,823 ppm) and lead (mean = 8.9 +/- 5.8 ppm) concentrations than the island flying foxes (mean [Fe] = 174 +/- 173 ppm, mean [Pb] = 1.9 +/- 0.5 ppm). Hepatic iron concentrations significantly correlated with tissue lead concentrations, histologic grading for iron and necrosis, serum iron, transferrin saturation, and plasma ferritin (P < 0.001). Blood lead concentrations negatively correlated with tissue lead concentrations (P < 0.001). When the product of transferrin saturation and serum iron was greater than 51, an individual animal had a high probability of having iron overload. When the product of these two variables was greater than 90, there was a high probability that the animal had hemochromatosis. On the basis of this study, it appears that evaluation of serum iron, transferrin saturation, and plasma ferritin are useful and noninvasive methods for diagnosis of hemochromatosis in Egyptian fruit bats.     

Iron Status and Erythrocyte Volume in Dogs With Congenital Portosystemic Vascular Anomalies

Microcytosis, hypochromasia, and low mean corpuscular hemoglobin are frequent hematologic abnormalities in dogs with portosystemic vascular anomalies (PSVA). The relationship of iron status to these abnormalities is unclear. We evaluated iron status and hematologic and biochemical parameters in dogs with congenital PSVA before (25 dogs) and after (11 dogs) partial ligation of the vascular anomaly. Serum iron concentration and total iron binding capacity were subnormal in 56% and 20% of dogs with PSVA, respectively. Transferrin saturation was normal in 68%, decreased in 20%, and increased in 12% of the dogs. Plasma ferritin concentration was either normal (56%) or high (44%), and was not associated with increases in ceruloplasmin concentration. Hepatic stainable iron was increased in 10 of 16 dogs. Mean corpuscular volume (MCV), mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration were decreased in more than 60% of dogs with PSVA. Serum biochemical abnormalities included high bile acid concentration and alanine transaminase (ALT) and alkaline phosphatase (ALP) activities; and low urea, creatinine, cholesterol, and total protein concentrations. Serum iron concentration and clinical status (normal or PSVA) significantly influenced MCV ( P = .003 and P < .001, respectively), whereas age, ceruloplasmin, ferritin, cholesterol, bile acids, and total iron binding capacity did not. Partial ligation of PSVA was associated with resolution of clinical signs and the return to normal of iron status and all clinicopathologic abnormalities, except total fasting bile acid concentrations. These findings indicate that iron status is frequently abnormal in dogs with PSVA and that low serum iron concentration appears to be related to the development of microcytosis. The normalization of iron status and clinicopathologic abnormalities after treatment suggests that they are direct consequences of PSVA.     

Characterization of erythrocytic indices and serum iron values in healthy llamas.

An electronic particle counter with attached particle-size analyzer was configured to directly determine concentration, mean cell volume, and volume distribution of erythrocytes in llama blood. Blood from 38 healthy llamas was used to characterize erythrocytic measurements and serum iron values for this species. Volume distribution curves for llama erythrocytes were similar in shape to those of other species. These curves had a unimodal, symmetric shape with a tail skewed to the right. Reference ranges for directly measured mean cell volume, erythrocyte concentration, hemoglobin concentration, and mean cell hemoglobin concentration were 21 to 28 fl, 11.3 x to 17.5 x 10(6) cells/microliters, 12.8 to 17.6 g/dl, and 43.2 to 46.6 g/dl, respectively. Reference ranges for serum iron concentration, total iron-binding capacity, and transferrin saturation were determined to be 70 to 148 micrograms/dl, 230 to 370 micrograms/dl, and 22 to 50%, respectively.     

Iron content of rat serum ferritin.

The serum ferritin concentration was significantly higher in female than in male rats, reflecting higher iron stores in females than in males. The mean iron/protein ratio of serum ferritin was 0.018+/-0.008 (SD) (microg of Fe/microg of protein) in female rats and 0.011+/-0.011 in male rats, being much lower than that of liver ferritin (0.233+/-0.014 in females and 0.227+/-0.020 in males). Iron loading of rats significantly increased serum ferritin concentration, but did not influence the iron content of serum ferritin. These results indicate that rat serum ferritin contains only a small amount of iron independent of body iron stores.     

Effect of repeated phlebotomy on iron status of rhesus monkeys (Macaca mulatta).

Iron status, as determined by hematologic values, serum iron concentration, total iron-binding capacity, and zinc protoporphyrin concentration, was determined in 2 groups of 6 nonpregnant monkeys. Monkeys of groups 1 and 2 had 10 and 5%, respectively, of their blood volume withdrawn per week for up to 10 weeks or until blood hemoglobin concentration was less than or equal to 10 g/dl. A third group of 6 monkeys served as controls. The majority (8/12) of the monkeys became anemic (hemoglobin concentration, less than or equal to 10 g/dl) after approximately 30 to 70% (mean, 49%) of their blood volume was removed. Anemia was accompanied by decrease in serum iron concentration and percentage of transferrin saturation. Microcytosis, hypochromasia, and increased zinc protoporphyrin concentration, all hematologic characteristics of iron deficiency, developed later. The calculated iron stores ranged from 1 to 133 mg, with mean value of 51 mg. Iron-depleted monkeys had mean calculated available iron store of 20.8 mg, whereas iron-replete monkeys had mean available iron store of 114.0 mg. Changes were not observed in monkeys of the control group during the study period. None of the baseline hematologic or biochemical analytes measured were good predictors of iron stores. The diet used at the research center did not provide sufficient iron to prevent iron deficiency in most of the monkeys from which a total amount of 30 to 70% of blood volume at 5 or 10%/week was withdrawn. Studies requiring that much blood may need to be modified to include iron supplementation, reduction of sample volume, or iron replacement after termination of projects.     

Study of the effect of total serum protein and albumin concentrations on canine fructosamine concentration.

The relationship among serum fructosamine concentration and total serum protein and albumin concentrations were evaluated in healthy and sick dogs (diabetics and dogs with insulinoma were not included). Fructosamine was determined using a commercial colorimetric nitroblue tetrazolium method applied to the Technicon RA-500 (Bayer). Serum fructosamine concentration was not correlated to total protein in normoproteinemic (r = 0.03) and hyperproteinemic dogs (r = 0.29), but there was a high correlation (r = 0.73) in hypoproteinemic dogs. Similar comparison between serum fructosamine and albumin concentrations showed middle correlation (r = 0.49) in normoalbuminemic dogs and high degree of correlation (r = 0.67) in hypoalbuminemic dogs. These results showed the importance of recognizing serum glucose concentration as well as total serum protein and albumin concentrations in the assay of canine serum fructosamine concentration.     

Plasma ferritin of sows during pregnancy and lactation

We studied a set of indicators of iron metabolism in sows and new-born piglets: hemoglobin, plasma iron, total iron binding capacity and plasma ferritin. Iron status of seventy-two sows was studied throughout pregnancy and lactation. The results point to mobilization of iron from its storage sites up to the second month of gestation, but no appreciable decrease during the second half of pregnancy. No appreciable mobilization of the iron stores of sows was observed during the lactation period. Nine sows and their 78 piglets were used to compare the status of iron in the sows and the end of gestation with the iron status of the piglets at birth; there was a positive correlation between the mean values of plasma ferritin concentration in the piglets and the levels of plasma ferritin in their mothers.     

Enzyme-linked immunosorbent assay for canine serum ferritin, using monoclonal anti-canine ferritin immunoglobulin G

Immunoassay of serum ferritin is currently used to evaluate the clinical iron status of human beings, horses, cattle, and swine. Because ferritins are immunologically species specific, a separate assay must be developed for each species. We have developed an ELISA for serum ferritin in dogs, using a monoclonal anti-canine ferritin antibody. Ferritin standards were linear (r = 0.997) from 0 to 80 ng/ml. Recovery of ferritin from canine serum was 94%. Dilutions of pooled canine serum were linear from 0 to 50% (r = 0.994). Within-assay coefficient of variability was 5.5%, whereas assay-to-assay coefficient of variability ranged from 12.5 to 21%. This assay should provide a nonsurgical means of accurately estimating dogs' iron stores.     

Desferoxamine and iron dextran in acute Salmonella cholerae-suis infection in pigs

Serum iron (SI)-related and hematologic changes were evaluated in a herd of weaned pigs inoculated with a strain of Salmonella cholerae-suis, causing 83% mortality within 22 days after inoculation was done. Serum iron concentrations decreased to 35% of base-line values 2 days after inoculation was done, but recovered to near base line subsequently. Total SI-binding capacity (TIBC) decreased gradually for 14 days after inoculation was done. Transferrin (TF) concentrations decreased to near half the base line throughout the postinoculation observation period. The calculated SI saturation coefficient decreased to half the base line, but recovered to or above the base-line value subsequently. Combined observations of SI, TIBC, TF, and SI saturation coefficient concentrations indicated that there was higher saturation of host iron-binding proteins and recruitment of additional iron-binding systems subsequent to 2 days after inoculation was done. Day 2 after inoculation seemed to be a critical period for host iron metabolism. Injection of supplemental iron dextran simultaneously with Salmonella infection resulted in lower mortality of iron-injected pigs (P less than 0.005). A highly significant negative correlation was observed between SI concentration and rectal temperatures after pigs were inoculated with Salmonella (r = -0.54; P less than 0.0001). Hemoglobin concentrations, mean corpuscular volume, and mean corpuscular hemoglobin were not significantly affected by Salmonella infection or iron injection concurrent with Salmonella infection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of vaccination on serum concentrations of total and antigen-specific immunoglobulin E in dogs

OBJECTIVE: To determine the effect of vaccination on serum concentrations of total and antigen-specific IgE in dogs. ANIMALS: 20 female Beagles. PROCEDURE: Groups of 5 dogs each were vaccinated repeatedly between 8 weeks and 4 years of age with a multivalent and rabies vaccine, a multivalent vaccine only, or a rabies vaccine only. A fourth group of 5 dogs served as unvaccinated controls. Serum concentrations of total immunoglobulins and antigen-specific IgE were determined following vaccination. RESULTS:-The multivalent vaccine had little effect on serum total IgE concentrations. The concentration of IgE increased slightly following vaccination for rabies at 16 weeks and 1 year of age and increased greatly after vaccination at 2 and 3 years of age in most dogs, with a distinct variation between individual dogs. Vaccination had no effect on serum concentrations of IgA, IgG, and IgM as measured at 2 and 3 years of age. The rabies vaccine contained aluminum adjuvant in contrast to the multivalent vaccine. An increase of IgE that was reactive with vaccine antigens, including bovine serum albumin and bovine fibronectin, was detected in some of the dogs vaccinated for rabies. There was no significant correlation between serum concentrations of total IgE and antigen-specific IgE following vaccination. Serum total IgE concentration rapidly returned to preimmunization concentrations in most dogs, but high concentrations of antigen-specific IgE persisted. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination of dogs for rabies increases serum concentrations of total IgE and induces IgE specific for vaccine antigens, including tissue culture residues. Vaccination history should be considered in the interpretation of serum total IgE concentrations.     

Anemia of inflammation in dogs infected with Ehrlichia platys

Ten adult male dogs were inoculated with Ehrlichia platys, and blood samples were collected throughout the infection to evaluate the hematologic changes with respect to serum biochemical analytes. All dogs developed a mild, normocytic, normochromic anemia by postinoculation day 7, with significantly (P less than 0.05) decreased serum iron concentration and total iron-binding capacity. Stainable bone marrow iron appeared normal or increased throughout the infection. By postinoculation day 31, the PCV was not significantly different from the pretreatment value. All dogs became hypergammaglobulinemic, leukopenic, hypoalbuminemic, and hypocalcemic during the infection. These findings were compatible with the syndrome of anemia of inflammation.     

Mucosal uptake,mucosal transfer and retention of iron in veal calves

A method for studying iron absorption in humans was adapted to veal calves. Three 10-week-old calves with moderate (calves 1 and 2) or severe (calf 3) iron deficiency were given an abomasal injection of⁵⁹Fe and⁵¹Cr and all their faeces were collected over 15 days in order to measure mucosal uptake, mucosal transfer and retention of iron. The mucosal uptake was 62.2, 53.4 and 71.8% in calves 1, 2 and 3, respectively. The iron retention measured 14 days after administration of the test dose was 57.4, 52.3 and 56.4% in calves 1, 2 and 3, respectively. Maximal plasma activity was found in all three calves between 1 1/2 and 2 h after injection of the test dose. The plasma activity decreased rapidly, with a slight increase between the 5th and the 10th hour. After 21 h, less than 0.25% of the injected dose was still present in 1 litre of plasma. Not all the⁵¹Cr was recovered in the faeces. No⁵⁹Fe was found in the urine but some⁵¹Cr could be detected. The results of this study show that the method described is useful for measuring the different steps of iron absorption in iron-deficient veal calves.Abbreviations Hb haemoglobin concentration - MCV mean corpuscular volume - PCV packed cell volume - PI plasma iron - RBC red blood cell count - R iron retention - TIBC total iron-binding capacity - TIBC-SAT saturation of the total iron-binding capacity - U mucosal uptake