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At least 325 records · Page 18Linked to original sources

PubMed2007

Blood vitamin concentrations in privately owned dogs fed non-standardized commercial diets and after intake of diets with specified vitamin concentrations.

The objective was to investigate in a survey study the blood vitamin concentrations in healthy dogs fed non-specified commercial complete diets and in an intervention study to determine the effects of defined dietary vitamin intakes on blood vitamin levels and hair and skin condition. Sixty-four privately owned dogs, aged from 1 to 8 years, without history of skin or coat problems were included. All animals were fed commercial complete diets with uncertain vitamin concentrations before enrolment. The animals were assigned, according to weight and gender, to four groups with graded vitamin intakes. The blood vitamin levels and skin and coat quality of the dogs were investigated at days 0 and day 122. Coat and hair condition was not influenced by the experimental diets. The retinol concentrations were reduced at the end of the experiment compared with the baseline levels, retinyl esters were not influenced. 25-Hydroxycholecalciferol decreased in all groups, alpha-tocopherol was constant or tended to decrease. Ascorbic acid, thiamine pyrophosphate and riboflavin concentrations were not affected by treatment, flavin adenine dinucleotide and pyridoxal-5'-phosphate were partially reduced on day 122. Cobalamin, pantothenate and biotin concentrations increased with higher dietary intakes, folate levels in tendency. In conclusion, this study gives a survey of blood vitamin concentrations in healthy dogs and provides a data base for the evaluation of the vitamin status in health and disease.

Animal Feed↗

PubMed1996

Concentration--effect and concentration--toxicity relations with lamotrigine: a prospective study.

This prospective study was designed to ascertain whether measurement of lamotrigine (LTG) concentrations in the epilepsy clinic could be used to predict the onset of complete seizure control or the emergence of adverse effects. LTG was initiated in doses of 25 or 50 mg daily in 69 patients with newly diagnosed or poorly controlled epilepsy and was increased monthly in 50-mg increments until the patient became seizure-free for at least 6 months or developed adverse effects that abated after a reduction in dosage. LTG and other antiepileptic drug (AED) concentrations were measured at each clinic visit but were not supplied to the investigator examining the patients. Overall, 19 patients either withdrew due to lack of efficacy or defaulted from the clinic. Of the remaining 50 patients, 32 (19 monotherapy, 13 polytherapy) became seizure-free at widely varying daily LTG doses (median 200 mg, range 25-850 mg) and concentrations (median 3.8 mg/L, range 1.4-18.7 mg/L). Likewise, the 18 patients (5 monotherapy, 13 polytherapy) who experienced intolerable side effects showed substantial variations in daily LTG doses (median 300 mg, range 100-900 mg) and concentrations (median 4.0 mg/L, range 0.4-18.5 mg/L). No useful concentration-effect or concentration-toxicity relation with LTG could be demonstrated in this study; therefore, we believe that routine therapeutic drug monitoring with this new AED is not currently indicated.

Adolescent↗

PubMed2006

Ischemia-modified albumin concentrations should be interpreted with caution in patients with low serum albumin concentrations.

OBJECTIVE: Ischemia-modified albumin (IMA((R))) is a novel marker for assessing cardiac ischaemia. We assessed the relationship between total albumin concentrations and IMA in serum to investigate whether interpretation of IMA was albumin-dependent. SUBJECTS AND METHODS: 298 serum samples were assayed for total albumin (albumin), using bromcresol purple, and IMA, using an indirect colorimetric assay. Correlations were investigated for the whole data set and for two subgroups, those samples with low albumin (< or =34 g/l) and those with albumin within the reference interval. RESULTS: There was a significant (r = -0.888, p < 0.0001) negative correlation between IMA and albumin both over the entire range of albumin concentrations and in the low albumin concentration subgroup (r = -0.85, p < 0.0001); however, there was less significant correlation in the subgroup with albumin within the reference interval (r = -0.37, p < 0.0001). CONCLUSION: A negative correlation exists between IMA and albumin concentrations; however, there is less significant correlation when albumin is within the reference interval. IMA concentrations determined in patients with albumin concentrations < or =34 g/l should be interpreted with some caution.

Adolescent↗

PubMed2005

Large concentrations of nitrous oxide decrease the isoflurane minimum alveolar concentration sparing effect of morphine in the rat.

Many adjuvant drugs have demonstrated anesthetic-sparing properties when combined with volatile anesthetics. Nitrous oxide is combined with volatile anesthetics to reduce the concentrations of volatile anesthetics required to produce anesthesia. Analgesic doses of opioids clearly reduce the requirement for inhaled anesthetics in both human patients and experimental animals. We performed this study to determine whether the combination of nitrous oxide and morphine decreased isoflurane minimum alveolar anesthetic concentration (MAC) even further in the rat. Fifty-eight female rats were used. The rats were divided into 8 groups: isoflurane in 4 possible nitrous oxide concentrations (0%, 30%, 50%, or 70%) with saline or morphine (1 mg/kg). Then the MAC of isoflurane (MAC(ISO))was determined from alveolar gas samples at the time of tail clamp. The MAC of isoflurane was significantly different at each nitrous oxide concentration, and increasing nitrous oxide concentrations reduced anesthetic requirements for isoflurane. The administration of morphine reduced the MAC(ISO) when used with 0% or 30% nitrous oxide. This MAC(ISO) by morphine reduction was less with 50% nitrous oxide and nonexistent at 70% nitrous oxide. However, with morphine present the MAC(ISO) was independent of the nitrous oxide concentration in the 30%-70% range.

Analgesics, Opioid↗

PubMed2005

Effect of maternal smoking on breast milk interleukin-1alpha, beta-endorphin, and leptin concentrations and leptin concentrations.

Tobacco smoke is immunotoxic, but the effect of smoking on the immunologic function of the mammary gland of mothers who smoke cigarettes ("smoker mothers") has not been studied. Our objective was to test, in smoker mothers, the colostral and transitional milk concentrations of interleukin-(IL)1alpha. The immunomodulators beta-endorphin and leptin were also tested. Pregnant women who self-identified as smokers (greater than or equal to 5 cigarettes per day through pregnancy) or nonsmokers were recruited for study participation. The study population included 42 smoker and 40 nonsmoker nursing mothers, with otherwise uncomplicated gestation, delivery, and puerperium, who were breast-feeding ad libitum their healthy neonates. Colostrum was obtained on the third postpartum day at 0900 hr and transitional milk on the 10th postpartum day at 0900 hr. IL-1alpha concentrations were significantly reduced in the colostrum of smoker mothers compared with nonsmoker mothers (p < 0.01). Colostral beta-endorphin and leptin concentrations were comparable. No significant differences were found between smoker and nonsmoker lactating mothers in transitional milk concentrations of IL-1alpha, beta-endorphin, and leptin. Moreover, beta-endorphin and leptin concentrations were significantly reduced in transitional milk samples compared with colostrum of both smoker and nonsmoker mothers (p < 0.05); also, IL-1alpha transitional milk concentrations were reduced compared with colostrum, but without any significance. This analysis shows that maternal smoking alters the colostral milk levels of the proinflammatory cytokine IL-1alpha. The altered postnatal provision of alternative source of the proinflammatory cytokine IL-1alpha adds understanding to how breast-feeding could be nonprotective against infections among the neonates nursed by smoker mothers.

Adult↗

PubMed1995

Utilization of plasma and urine methadone concentration measurements to limit narcotics use in methadone maintenance patients: II. Generation of plasma concentration response curves.

Controversy exists still concerning the proper daily dose of methadone required to eliminate illicit narcotics use. To address this, urine methadone and opioid concentrations were measured prospectively (150 maintenance patients, 18 month period, 9250 urine samples) using fluorescence polarization immunoassay. Results demonstrate that current thresholds (EMIT uses 300 micrograms/L) defining opiate positive urines are overly high (FPIA can go as low as 25 micrograms/L), causing severe underestimation of opioid use in the typical clinic. Using this data, plasma methadone concentration and dose response probability curves were generated for illicit opiate use. Results demonstrate a S-shaped, 24 hr trough plasma methadone concentration response curve with effective concentrations, EC90 = 80 micrograms/L, EC98 = 600 micrograms/L. Plotting mean plasma methadone concentration versus dose gives a monotonically increasing function: Conc = 5.367*dose0.858, raw R-squared = 0.967, corrected R-squared = 0.802. Unfortunately, coefficients of variation for plasma concentrations at each prescribed dose are unacceptably large, explaining poor dose response relationships for some patients.

Adult↗

PubMed1990

Immunoreactive plasma cholinesterase (EC 3.1.1.8) substance concentration, compared with cholinesterase activity concentration and albumin: inter- and intra-individual variations in a healthy population group.

Substance concentrations of plasma cholinesterase (EC 3.1.1.8) were measured in 94 healthy individuals without occupational exposure to known inhibitors (six samples from each individual). Immunoreactive cholinesterase substance concentrations showed an inter-individual variation corresponding to CVtotal = 22% (mean: 5.01 mg/l, SD: 1.11 mg/l). Intra-individual variations of immunoreactive cholinesterase substance concentration were correlated (r = 0.36) to intra-individual variation of albumin. Estimated by a repeated-measures analysis of variance, the observed intra-individual variation of cholinesterase substance concentration corresponded to CV = 8.8% (SD: 0.44 mg/l), which together with a CVerror = 6% (within and between runs), implies a biological intra-individual variation of cholinesterase substance concentration corresponding to CVintra = 6.4%. Specific catalytic activity (kU/mg immunoreactive cholinesterase) was influenced by the ChE-1 phenotype (phenotype U: 1.58 kU/mg, phenotype UA: 1.22 kU/mg), but not by body weight, height, age, and sex. Observed intra-individual variation of specific catalytic activity corresponded to 6.4% (SD: 0.10 kU/mg), which together with an estimated CVerror = 6.2% implies the biological intra-individual variations of specific catalytic cholinesterase activity to be insignificant. The insignificant CVintra makes specific catalytic cholinesterase activity a rational quantity for evaluation of unexpected fluctuations of cholinesterase activity concentrations.

Adult↗

PubMed1996

Domestic cats show episodic variation in plasma concentrations of adrenocorticotropin, alpha-melanocyte-stimulating hormone (alpha-MSH), cortisol and thyroxine with circadian variation in plasma alpha-MSH concentrations.

Blood samples were collected from 31 healthy domestic cats to characterize possible episodic and/or circadian variation in plasma concentrations of adrenocorticotropin (ACTH), cortisol, thyroxine and alpha-melanocyte-stimulating hormone (alpha-MSH). Samples were collected with minimal disturbance through indwelling jugular cannulae at two frequencies: at 20-min intervals for 3 h for evaluation of episodic variation, and at 2-h intervals for 48 or 72 h to identify possible circadian changes. Episodic peaks in profiles of all hormones were found in the majority of cats. When data were compared across four bleed periods (each of 3 h duration), no differences were detected in average hormone concentrations or characteristics of episodic pulses. Correlation analyses showed a significant (p < 0.001) relationship between concentrations of ACTH and cortisol (r = 0.44) when these hormones were measured in the same plasma sample. A weaker but significant correlation (r = 0.13, p < 0.05) was also detected between concentrations of ACTH and alpha-MSH, suggesting that proopiomelanocortin peptide secretion from the pars distalis and pars intermedia occurs at least on occasion in synchrony. No differences in hormonal profiles were noted when comparing data across sexes. Data from the studies designed to evaluate circadian change (48 and 72-h bleed periods) indicated that, of the four hormones, only concentrations of alpha-MSH changed with a significant circadian periodicity. A significant circadian component of period length 24-25 h was detected in 37% (seven of 19) of cats examined. Concentrations of alpha-MSH were greatest coincident with or shortly after the onset of darkness. These findings indicate that pituitary-adrenocortical hormones are secreted episodically in domestic cats and that, in contrast to the patterns shown by ACTH and cortisol, secretion of the pars intermedia product alpha-MSH occurs with a circadian rhythm in about one-third of cats.

Adrenocorticotropic Hormone↗

PubMed1993

Theophylline target concentration in severe airways obstruction - 10 or 20 mg/L? A randomised concentration-controlled trial.

The optimal serum concentration of theophylline for the management of acute airways obstruction was evaluated by comparing the response to target concentrations at the extremes of the usual therapeutic range. 174 patients requiring intravenous theophylline were randomly assigned to a target concentration of 10 or 20 mg/L. Control of theophylline dosage using measured theophylline concentrations and evaluation of efficacy and toxicity was performed under double-blind conditions. 87 patients (50%) required hospital admission. Of these, 54 patients (62%) were followed throughout their hospital admission and reviewed at an outpatient clinic approximately 1 week after discharge. The duration of hospital stay, and rate and extent of improvement in peak expiratory flow rate were not different between the groups. There was significantly more toxicity in the 20 mg/L group. The initial target concentration for theophylline in the management of acute airway obstruction should be 10 mg/L under circumstances where concentration is used to control theophylline dosages.

Adult↗

PubMed1997

Efficacy of newly developed pressure swing adsorption type oxygen concentrator with membrane humidifier: comparison with conventional oxygen concentrator with bubble water humidifier.

To examine the clinical efficacy of a newly developed pressure swing adsorption (PSA) type oxygen concentrator with a membrane humidifier without added water for humidification, the new machine was compared with the conventional PSA type oxygen concentrator with bubble water humidifier in 10 patients with chronic pulmonary disease. Relative humidity, partial pressure of oxygen (PaO2) and partial pressure of carbon dioxide (PaCO2) in arterial blood were measured when the patient breathed air and oxygen from the oxygen concentrators. No significant difference between PaO2 while breathing oxygen flow from the new machine and that while breathing oxygen from the conventional oxygen concentrator was observed. All patients answered that there was no difference on subjective impression between breathing oxygen from the new machine and from the conventional oxygen concentrator. Sufficient relative humidity (above 50%) of oxygen flow was obtained by using membrane humidifier. Since this machine saves the troublesome procedures of cleaning the container and changing the water, it will be beneficial to the patients who use a PSA-type oxygen concentrator in their home.

Aged↗

PubMed2004

Intercellular adhesion molecule-1 concentration is genetically correlated with insulin resistance, obesity, and HDL concentration in Mexican Americans.

The metabolic syndrome and type 2 diabetes are associated with endothelial activation (and thus with inflammatory processes leading to atherosclerosis), but the mechanisms that underlie these associations are not fully understood. Endothelial intercellular adhesion molecule (ICAM)-1 plays an important role in the recruitment of immune cells during the development of atherosclerotic plaque and is a marker of inflammatory disease. We performed bivariate quantitative genetic analyses to estimate genetic and environmental correlations between circulating ICAM-1 concentration and 17 phenotypes associated with the metabolic syndrome. Our study population comprised 428 adults in 20 extended Mexican-American families from the San Antonio Family Heart Study (SAFHS). Circulating ICAM-1 concentration is heritable (h(2) = 0.56). ICAM-1 concentration showed significant positive genetic correlations (range 0.32-0.52, P < 0.05) with fasting insulin, insulin 2 h after oral glucose challenge, homeostasis model assessment of insulin resistance, BMI, waist circumference, and leptin concentration; negative genetic correlation with HDL3 cholesterol concentration; and negative environmental correlation with adiponectin concentration. Significant genetic correlations were not found between ICAM-1 and fasting or 2-h serum glucose or systolic or diastolic blood pressure. Thus, ICAM-1 expression may share common genetic modulation with traits related to obesity, insulin resistance, and HDL3 cholesterol, but not with hyperglycemia or hypertension per se.

Blood Glucose↗

PubMed2006

Comparison of variability in cardiorespiratory measurements following desflurane anesthesia at a multiple of the minimum alveolar concentration for each dog versus a multiple of a single predetermined minimum alveolar concentration for all dogs in a group.

OBJECTIVE: To determine whether the variability of cardiorespiratory measurements is smaller when administering desflurane at a multiple of the individual's minimum alveolar concentration (MAC) or at a predetermined, identical concentration in all subjects. ANIMALS: 10 dogs. PROCEDURES: Desflurane was administered at 1.5 times the individual's MAC (iMAC) and 1.5 times the group's MAC (gMAC). The order of concentrations was randomly selected. Heart rate, respiratory rate, arterial blood pressure, central venous pressure, mean pulmonary artery pressure, pulmonary artery occlusion pressure, arterial and mixed-venous blood gas tensions and pH, and cardiac output were measured. The desflurane concentration required to achieve a mean arterial pressure (MAP) of 60 mm Hg was then determined. Finally, the desflurane concentration required to achieve an end-tidal PCO(2) of 55 mm Hg was measured. RESULTS: Variances when administering 1.5 iMAC or 1.5 gMAC were not significantly different for any variable studied. Differences between the MAC multiples needed to reach an MAP of 60 mm Hg and the mean of the sample were significantly larger when gMAC was used, compared with iMAC, indicating that a multiple of iMAC better predicted the concentration resulting in a MAP of 60 mm Hg. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that, in a small group of dogs, variability in cardiorespiratory measurements among dogs is unlikely to differ whether an inhalant anesthetic is administered at a multiple of the iMAC in each dog or at an identical gMAC in all dogs.

Anesthetics, Inhalation↗

PubMed1993

Effect of concentration of mixed-function oxidase on concentration of estrogen, rate of egg lay, eggshell thickness, and plasma calcium in laying hens.

The objective of this study was to investigate the effect of induction or depression of mixed-function oxidases (MFO) by xenobiotics on the peripheral concentration of estrogens, plasma Ca, rate of egg lay, and eggshell thickness in laying hens. In Exp. 1, 100 mg of phenobarbital (PB) administered orally each day for 3 or 7 d reduced concentrations of estrone and estradiol (E2) in serum. In Exp. 2, 25, 50, or 100 mg of PB was administered orally to laying hens for 3 or 7 d. Treatment with 100 mg of PB for 3 d or with 25, 50, or 100 mg for 7 d significantly increased liver:body weight ratios. Microsomal protein increased after 7 d of 50 or 100 mg of PB administration. Feeding PB decreased concentration of E2 and total plasma Ca in a dose- and period-dependent manner. Concentration of E2 was reduced to 10% of control, whereas hepatic cytochrome P-450 increased significantly with dose. The correlation between concentration of E2 and P-450 was negative and significant. Total Ca in the plasma was highly, positively correlated with concentration of E2. Eggshells were thinner from hens treated with 100 mg of PB for both 3 or 7 d than those from control hens. Rate of egg lay was reduced by 100 mg of PB for 7 d. In Exp. 3, .5 mL of CCl4 given orally for 1 d decreased P-450 and increased E2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Effects of endophyte-infected fescue on concentrations of prolactin in blood sera and the anterior pituitary and concentrations of dopamine and dopamine metabolites in brains of steers.

An experiment was conducted to determine if the decrease in circulating concentrations of prolactin in cattle consuming endophyte (Acremonium coenophialum) -infected tall fescue (Festuca arundinacea) was associated with changes in prolactin concentrations in the anterior pituitary and concentrations of dopamine (DA) and its metabolites 3,4-dihydroxyphenyl-acetic acid (DOPAC) and homovanillic acid (HVA) in the stalk median eminence (SME), preoptic area (POA) and hypothalamus (HP). Six crossbred steers that grazed high-endophyte (greater than 90% infected) fescue and four steers that grazed low-endophyte (less than 1% infected) fescue from April to September were slaughtered. Brains and pituitaries were removed and dissected. Extracts from neural tissue were analyzed for DA, DOPAC and HVA using high performance liquid chromatography/electrochemical detection. Pituitary extracts and sera from blood samples taken 5 d prior to slaughter were subjected to prolactin radioimmunoassay. Consumption of high-endophyte fescue was associated with decreased concentrations of prolactin in serum (P less than .01) and in the anterior pituitary (P = .08), decreased (P less than .05) concentrations of DA in the SME and decreased (P less than .01) concentrations of HVA in the POA and HP, but it did not influence levels of DOPAC. These results suggest that endophyte toxins may reduce prolactin synthesis and release and may alter activity of dopaminergic neurons.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1994

Effect of clotting temperature and eosinophil concentration on the eosinophil cationic protein concentration in serum.

Earlier investigations have indicated the need for detailed instructions about the incubation conditions of blood samples before establishment of eosinophil cationic protein concentration in serum. Therefore, the effect of different clotting temperatures and eosinophil concentrations on the serum eosinophil cationic protein concentration was quantified in 40 subjects. Our results show that serum eosinophil cationic protein concentrations strongly depend on the clotting temperature. Blood samples clotted for 1 h at 37 degrees C had 5-10 times higher serum eosinophil cationic protein concentrations than blood samples of the same subject clotted for 1 h at 0 degrees C. Higher eosinophil counts resulted also in increased serum eosinophil cationic protein concentrations.

Blood Coagulation↗

PubMed1983

Serum and saliva concentrations of sulfamethoxazole and trimethoprim in adults and children: relation between saliva concentrations and in vitro activity against nasopharyngeal pathogens.

The combination sulfamethoxazole/trimethoprim (SMX/TMP) was given orally to 4 healthy adult volunteers in mean daily doses of 23.0/4.6 mg/kg body weight for 6 days. The serum and saliva concentrations of the drugs were assayed on days 1, 3 and 6. On the first day (0-12 h) there was no measurable concentration of SMX in the saliva. On days 3 and 6 the mean peak levels of SMX in saliva were 7.8 and 9.8 micrograms/ml, i.e. 8-9% of the corresponding mean peak serum levels. In contrast, the concentrations of TMP in saliva were more than twice as high as those in serum. The mean SMX/TMP ratios in saliva days 3 and 6 were 1.3 and 1.4, respectively, i.e. approximately one-twentieth of the mean SMX/TMP ratios in serum. SMX/TMP was also administered to children with serous otitis media. The drug concentrations in saliva were assayed 2-3 h after administration on days 6 and 9 of a 10-day course, with a mean daily dose of 34.5/6.9 mg/kg body weight. The mean saliva concentration of SMX in the children was slightly higher than in adults and the mean TMP concentration about half of that in adults. The mean SMX/TMP ratio in the children's saliva was 4.2. The in vitro activity of SMX/TMP 20:1 and 4:1 was determined against H. influenzae, D. pneumoniae, B. catarrhalis and group A streptococci. H. influenzae, D. pneumoniae and group A streptococci were found more susceptible to TMP than to SMX, while the reverse was true for B. catarrhalis. In the 3 former, the potentiation of SMX by TMP was more pronounced than was the potentiation of TMP by SMX, while the opposite was recorded for B. catarrhalis. The most beneficial effect of the SMX/TMP combination against nasopharyngeal pathogens was recorded for B. catarrhalis and the weakest effect for H. influenzae and group A streptococci. With the exception of B. catarrhalis, the administration of TMP alone to adults may be just as effective against nasopharyngeal pathogens as is the SMX/TMP combination in children.

Adult↗

PubMed1984

Effects of feeding frequency on glucose concentration, glucose turnover, and insulin concentration in steers.

Patterns of diurnal variation of glucose production, utilization, and concentration and of variation of insulin concentration in blood plasma were studied. Four Holstein steers (200 kg) were in a switchback design. Each received 4.6 kg of 70% chopped alfalfa hay and 30% dry cracked corn daily, either as two equal meals at 12-h intervals or 12 equal meals at 2-h intervals. None of mean daily glucose production, utilization, and concentration nor mean insulin concentration was affected by feeding frequency. In response to feeding, insulin was released simultaneously with increased glucose production, suggesting that glucose production and insulin release are regulated by a common effector system. Feeding twice daily resulted in a sinusoidal pattern of glucose specific radioactivity. On the basis of changes of glucose concentration, glucose utilization closely followed production. Within-day variation of glucose production for steers fed twice daily was greater than indicated by variation of glucose concentration. Such variation of production will lead to errors in estimates of glucose production from short (less than 12 h) isotope infusion experiments with steers fed twice daily. Conversely, daily glucose production was not different for steers fed twice or 12 times daily; therefore, frequent feeding is both necessary and appropriate for investigations of glucose kinetics.

Animals↗

PubMed1996

Effect of dietary iron concentration, age, and length of iron feeding on feed intake and tissue iron concentration of broiler chicks for use as a bioassay of supplemental iron sources.

Three experiments were conducted with day-old chicks to study the effects of dietary Fe concentration and age on Fe accumulation in tissues as an estimate of supplemental Fe bioavailability, and of delaying the time of initial high Fe supplementation up to 7 d of age on feed intake to 3 wk of age. In Experiment 1, chicks were fed a basal corn-soybean meal diet (188 mg/kg Fe, DM basis) or the basal supplemented with 400, 600, or 800 mg/kg added Fe as reagent grade FeSO4.7H2O for either 1, 2, or 3 wk. Dietary Fe depressed (P < 0.001) feed intake and body weight gain, especially at 3 wk. Kidney Fe concentrations increased linearly (P < 0.001) with increasing dietary Fe. Liver Fe concentration also increased linearly, but reached a plateau in birds fed 600 mg/kg Fe. Bone Fe increased linearly (P < 0.05) at 1 wk, but not at 2 or 3 wk. Liver and kidney Fe regressed on daily Fe intake had the best fit to a linear model at 2 wk. In Experiment 2, chicks were fed either a basal diet (320 mg/kg Fe, DM basis) continuously, the basal supplemented with 800 mg/kg added Fe as FeSO4.7H2O continuously, or were started on the control diet and switched to the high Fe diet on Day 3, 5, or 7. Feed intake was lower (P < 0.05) in birds started on Fe on Days 1 or 3, but delaying feeding of high Fe diets until Day 5 resulted in intake at 3 wk similar to that of birds fed the basal diet. In Experiment 3, the basal diet (123 mg/kg Fe) was fed to chicks for 6 d, then experimental diets were fed for 14 d. Diets were the basal or basal supplemented with 400, 600, or 800 mg/kg added Fe as reagent grade or feed grade Fe sulfate or an Fe methionine complex. When estimated from regression of log10 liver Fe concentration on total analyzed dietary Fe concentration, relative bioavailability was set at 100% for reagent grade Fe sulfate, and the feed grade sulfate was 92.3% and Fe methionine was 88.3%. Liver Fe concentrations may be useful criteria for determining Fe bioavailability and 2 wk of feeding was the optimal time required for such a bioassay. Delaying feeding high Fe diets until 5 d of age alleviated the decreased feed intake associated with high Fe diets.

Aging↗