Dietary Zinc Concentration Research Articles

Early growth and environmental implications of dietary zinc and copper concentrations and sources of broiler chicks

1. Environmental accumulation of zinc and copper is becoming a concern in areas having intensive animal production. This study examined performance and excretion of broiler chicks given diets supplemented with graded concentrations of zinc and copper from three different sources. 2. Two experiments were conducted, each utilising 570 1-d-old chicks. In Experiment 1, chicks were given diets containing supplemental zinc concentrations from 40 to 120 mg/kg supplied as zinc sulphate, a zinc amino acid complex (Availa®Zn), or a combination of zinc sulphate and Availa®Zn with each contributing one-half of the total supplemental zinc. In Experiment 2, broiler chicks were given diets with graded concentrations of supplemental copper ranging from 4 to 12 mg/kg from copper sulphate, a copper amino acid complex (Availa®Cu), or a combination of copper sulphate and Availa®Cu with each contributing one-half of the total supplemental copper. 3. During the 17-d experimental period, mineral concentration or source did not influence body weight, feed conversion, or the incidence of mortality from 1 to 17 d. 4. Decreasing dietary zinc concentration from 120 to 40 mg/kg reduced zinc excretion by 50%. 5. Copper excretion was decreased by 35% as supplemental copper was reduced from 12 to 4 mg/kg. 6. Reducing dietary zinc and copper concentrations can potentially decrease the accumulation of heavy metals in the environment without compromising bird performance.

The Effects of Dietary Zinc Concentration and Source on Yearling Bull Growth and Fertility

Yearling Angus bulls (n = 325) were allotted by BW into six pens of equal size. One of three dietary treatments consisting of 1) dietary Zn at 40ppm, all supplied by zinc sulfate (ZnS); 2) dietary Zn at 40ppm with 33.3% supplied by zinc proteinate and 66.6% supplied by ZnS (ZnPS); or 3) dietary Zn at 60 ppm, all supplied by ZnS (ZnHi) was delivered to two pen replicates. Initial and final liver biopsies were collected and analyzed for Zn concentration. Scrotal circumference and BW measures were collected at the start and conclusion of the trial. Semen from bulls intended for public sale (n = 167) was collected and evaluated for motility and morphological abnormalities. Bulls with percent normal sperm cell counts < 70% or with motility scores less than fair (motility scores = poor, fair, good, and very good) were considered classification deferred (CD). Following 126 d of treatment, bulls on the ZnHi treatment had a greater (P=0.06) increase in liver Zn concentration than bulls on the ZnS treatment, but not bulls on the ZnPS treatment (P=0.18) (‒9.8, 1.2, and 20.6ppm for ZnS, ZnPS, and Zn Hi, respectively). No differences in scrotal circumference or ADG were detected. Bulls receiving ZnPS had higher (P<0.05) percent normal sperm cells than did bulls receiving ZnS, but not bulls receiving ZnHi (55.5, 68.9, and 62.5% for ZnS, ZnPS, and ZnHi, respectively). The frequency of CD was less (P<0.05) for bulls on ZnPS and ZnHi treatments than for bulls on the ZnS treatment. In all fertility measures observed in this trial, bulls receiving the ZnPS rated greatest, followed by bulls on ZnHi, and lastly by bulls on ZnS.

Relative bioavailability of organic zinc sources based on tissue zinc and metallothionein in chicks fed conventional dietary zinc concentrations

An experiment was conducted to estimate relative bioavailability (RBV) of Zn in Zinc proteinate and Zinc methionine compared to Zinc acetate as the standard. A total of 432, 1-day-old male broiler chicks was assigned randomly to dietary treatments which included the basal maize–soyabean meal diet (24 mg Zn kg −1 DM) supplemented with 0, 30, 60, or 90 mg kg −1 added Zn as reagent grade Zinc acetate or 30 or 60 mg kg −1 added Zn from Zinc methionine or Zinc proteinate fed for 3, 6, or 9 days. Accumulation of Zn in bone increased ( P<0.001) with supplemental Zn and age. Bone Zn concentration was greater ( P<0.001) in chicks given Zinc proteinate. Hepatic and mucosal metallothionein (MT) increased ( P<0.001) with supplemented Zn and age. Using Zinc acetate as a standard (1.00) in multiple linear regressions gave estimated RBV values of 1.10, 1.24, and 1.16 for Zinc proteinate and 0.88, 0.91 and 0.78 for Zinc methionine at 3, 6, and 9 days, respectively, based on bone Zn concentrations. Similar estimates were calculated using mucosal MT. The coefficient of determination was greater for the mucosal MT regression at 3 days compared to that for bone Zn. Mucosal MT appears to be a suitable criterion to estimate bioavailability of Zn sources during short term trials.

Chronic vitamin E inadequacy and thermally treated oils affect the synthesis of hepatic metallothionein isoforms.

Metallothionein (MT)# synthesis can be stimulated in many organs not only by various metals such as cadmium, zinc, and copper, but also by many nonmetallic compounds or experimental conditions such as oxidative stress. The latter lead to the hypothesis that MT is induced in response to free radicals formed in tissues and lipid peroxidation. Whether the relationship between lipid peroxidation and MT synthesis is a common phenomenon also valid for lipid peroxidation induced by dietary factors such as chronic vitamin E inadequacy and autoxidation products of polyenoic fatty acids derived from thermally oxidized oil was investigated in the present study. The relationship between the induction of metallothionein isoforms I and II (MT-I and MT-II) in response to diet-induced lipid peroxidation using a rat model system in which lipid peroxidation was examined in vivo by chronic vitamin E inadequacy or by administration of lipid peroxidation products from a thermally treated polyenoicrich oil with either basal (dietary zinc concentration: 48 mg/kg; experiment 1) or Zn-stimulated MT levels (dietary zinc concentration: 305 mg/kg; experiment 2) was studied. In both experiments, growing male rats were fed diets containing either a fresh or a thermally treated soybean oil with deficient or sufficient amounts of vitamin E (14 and 11 vs. 648 and 560 mg alpha-tocopherol equivalents per kg diet) over 40 days according to a bifactorial experimental design. Plasma and liver concentrations of tocopherols and hepatic levels of thiobarbituric acid-reactive substances (TBARS) were measured by high performance liquid chromatography. MT isoform concentrations in rat liver were isolated and quantified by ion-exchange high performance liquid chromatography and atomic absorption spectrometry. Irrespective of the zinc supply, rats receiving inadequate amounts of vitamin E with the diet had markedly lower plasma and liver concentrations of alpha-tocopherol and total tocopherols than vitamin E-sufficient rats. ANOVA also revealed an interaction between the diet factors vitamin E and oil on tocopherols in plasma and liver of rats from both experiments. In experiment 1, where rats received normal amounts of dietary zinc, ingestion of the thermally treated oil impaired the tocopherol status compared to the treatment with the fresh oil, although this effect was only obvious in the vitamin E-deficient groups. In experiment 2, where rats received excessive amounts of zinc, the thermally treated oil did not contribute to a reduction of the tocopherol status in plasma and liver. In both experiments a significant increase in TBARS level, indicative of lipid peroxidation, was observed in the liver at chronic vitamin E inadequacy, but no effect of the oil was observed. Here, we show that the dietary treatments had some effects on the synthesis of liver metallothionein isoforms. In groups, receiving normal amounts of zinc, there was a significant interaction between the dietary treatments on the levels of MT-I and MT-II in liver. Chronic vitamin E inadequacy which was accompanied by diminished tocopherol levels in liver induced the synthesis of MT-I and MT-II. When vitamin E inadequacy was combined with the ingestion of a thermally treated polyenoic acid-rich oil hepatic levels of MT-I and MT-II remained low. In experiment 2, where rats were fed the high zinc diet, vitamin E inadequacy caused an increase of hepatic MT-I level just as in experiment 1, although this MT stimulating effect was irrespective of the oil. For MT-II there was a 43% increase in the vitamin E-deficient group fed the fresh oil compared to all the other groups, although this effect was not statistically significant. The liver MT isoform response to stress was similar in rats with basal MT levels and Zn-induced liver MT levels. The failing effect of the thermally treated oil on MT levels which were stimulated by vitamin E deficiency in experiment 2 wa

Effect of dietary zinc content and sources on the growth, body zinc deposition and retention, zinc excretion and immune response in chickens

1. In areas of intensive animal production heavy metals such as zinc (Zn), which is present at high concentrations in poultry excreta in relation to plant requirements, may be at the origin of soil phytotoxicity. This study was conducted in order to determine the effect of decreasing dietary Zn content on growth, plasma, tibia and whole body Zn concentrations, immune function, enzyme activity, Zn body retention and Zn concentration in excreta in broilers. 2. Two experiments were carried out using 160 and 80 1-day-old chicks. Broilers received diets with increased Zn contents of 20 to 190 mg/kg. In experiment 1, two sources of zinc methionine were compared to zinc sulphate. 3. A dietary Zn concentration of 45 mg/kg was sufficient to obtain normal broiler performance at 21 d of age. 4. Tibia and plasma Zn concentrations increased linearly with Zn dietary content and reached a plateau at 75 mg/kg, whereas the whole body Zn was saturated when the dietary Zn content was 90 mg/kg. 5. Antibody titres in response to SRBC injection and plasma alkaline phosphatase activity were not affected by dietary zinc concentration. 6. When the dietary Zn content was decreased from 190 to 65 mg/kg, body Zn retention was increased from 8% to 20% and Zn concentration in broiler manure was reduced by 75%. 7. Zn sources had no effect on the parameters measured in this study. 8. A nutritional approach, that is by lowering dietary Zn supplementation may reduce the risks of phytotoxicity in the soil resulting from excessive Zn concentration in manure.

Effects of dietary chromium, copper and zinc on femur fracture force and femur calcium concentration in male Japanese quail

The effects of dietary chromium, copper and zinc on femur fracture force and femur calcium concentration were evaluated in male Japanese quail, Coturnix coturnix japonica, using a three-factor response surface design. Quail were randomly assigned to one of fifteen experimental diets containing variable concentrations of dietary chromium (71 to 1124 ng/g diet), copper (1.6 to 8.3 μg/g diet), and zinc (11 to 51 μg/g diet). After six weeks femurs were removed, weighed and frozen for future analysis of femur fracture force and femur calcium concentration. Femur fracture force was significantly influenced by the interaction between dietary zinc and copper. In addition, bone calcium concentration was significantly affected by the quadratic effects of dietary zinc and copper.

Effect of high dietary zinc concentration and length of zinc feeding on feed intake and tissue zinc concentration in sheep

Two experiments were conducted to study the effect of high dietary Zn concentration and length of Zn feeding on feed intake and tissue Zn concentration in sheep. In Experiment 1, 24 whethers were fed a basal diet containing 41 mg kg −1 Zn dry matter (DM) basis and supplemented with 0, 500, 1000, 1500, 2000, or 2500 mg kg −1 Zn as reagent grade ZnSO 4 · 7H 2O for 10 days and voluntary feed intake was measured daily. There was no difference in average feed intake among treatment groups. Intake of feed decreased between Day 2 and Day 5 for sheep given most diets, but recovered thereafter. In Experiment 2, 27 wethers were supplemented with 700, 1400, or 2100 mg kg −1 Zn added to the basal diet containing 30 mg kg −1 Zn (DM basis) for either 10, 20, or 30 days, in a 3 × 3 factorial arrangment of treatments. Three additional sheep were killed at the start of the experiment to serve as controls for tissue Zn concentration. Feed intake did not differ among treatments. There was no difference in bone, heart, or muscle Zn due to dietary treatment or time. Liver and kidney Zn increased with increasing dietary Zn and length of feeding period. Spleen Zn also increased with dietary Zn. The best fits to a linear model were found for liver and kidney Zn concentration at 20 days. These tissues appear to be the most sensitive for future Zn bioavailability studies with ruminants.

Zinc-and/or cadmium-induced intestinal metallothionein and copper metabolism in adult rats

Feeding diets with high zinc or cadmium concentrations to animals compromises their copper status. Previous work suggested that metallothionein (MT), induced in the intestinal mucosa by zinc or cadmium, binds copper and inhibits its absorption. More recent studies showed that this mechanism may not be operative for zinc and that intestinal MT adapts to long-term feeding of high-zinc diets. The present study was designed to determine the effects of feeding high-zinc and/or high-cadmium diets on the induction of intestinal MT and its subsequent effect on copper status. Six-week-old male rats were placed in a 2 × 2 × 3 factorial experiment with two concentrations of dietary zinc (60 and 350 mg/kg), two concentrations of dietary copper (3 and 9 mg/kg), and three concentrations of dietary cadmium (0, 1, and 5 mg/kg). After 3 weeks, the difference in the MT concentration between rats fed high- and normal-zinc diets was only 1.5 times. However, rats fed the highest amount of cadmium had MT concentrations about five time higher than those not fed cadmium. In both the zinc and cadmium groups, the concentration of intestinal zinc and cadmium followed that of MT; however, the copper concentrations were not changed. Although intestinal MT was not elevated appreciably in zinc-fed rats, the copper status of these rats fed 3 mg of copper/kg of diet was severely depressed. Rats fed 9 mg of copper/kg of diet were not affected. The copper status in rats fed high-cadmium and 3 mg of copper/kg of diet was depressed even more than with a high-zinc diet. This study suggests that the effects of high dietary zinc or cadmium on copper status are not the result of induced intestinal MT binding of copper thus preventing its passage into the circulation.

Interspecific comparisons of relative assimilation efficiencies for zinc and cadmium in an ecological series of talitrid amphipods (Crustacea).

A dual-labelling radioisotope technique has enabled the relative assimilation efficiencies of an essential (Zn) and a non-essential trace metal (Cd) to be determined in an ecological series of talitrid amphipods from low-shore to fully terrestrial habitats. All species exhibited high assimilation efficiencies for zinc and cadmium (within the range 66.7-96.4%). Interspecific differences in assimilation rates showed no trend with increasing terrestriality of the habitat. Elevated dietary zinc concentrations failed to enhance zinc assimilation efficiency. Incorporation of antibiotics into the diet to eliminate gut microflora did not affect zinc assimilation efficiencies. The implications of having high trace-metal assimilation efficiencies are discussed in terms of land invasion by talitrids.

The effect of dietary vitamin D metabolites and zinc on normal and ectopic bone formation in weanling rats

The effect of dietary supplementation of rats with vitamin D metabolites and zinc was examined in selected bones and a short-term in vivo implant model. A 2×2×3 factorial design was utilized with two vitamin D metabolites (cholecalciferol-D 3 or 1,25-dihydroxycholecalciferol-1,25(OH) 2D 3); two levels of dietary zinc (marginal-4.5, and adequate-10 ug/g diet); and three time periods (11, 14 and 21 days after implantation). Seventy-two female weanling Long-Evans rats were fed their respective diets for three weeks before subcutaneous implantation with demineralized bone powder. The animals were injected intraperitoneally with 45Ca (0.5uCi/g body weight) 14 h before sacrificing. The ectopic bone implants as well as the femurs, tibias, humeri, scapulas and mandibles were obtained 11, 14 and 21 days following implantation. Implants were fixed, sectioned and stained with toluidine blue. The specific bones and the implants were analyzed for calcium, zinc and 45Ca. There was higher calcium concentration in the femurs of animals fed D 3 compared to 1,25(OH) 2D 3. Activities of enzymes (alkaline phosphatase-marker for formation, and acid phosphatase-marker for resorption) were quantitated in the implants. Enzyme activities, mineral deposition and presence of osteoblasts and osteoclasts all provided definitive evidence that the implant system was mimicking the typical dynamic processes normally occurring in bone tissues. An interaction between the form of vitamin D (D 3 vs 1,25(OH) 2D 3) and level of zinc fed to the rats was demonstrated in the implants; calcium and zinc concentrations were higher in the implants of rats fed D 3 and adequate zinc than rats fed 1,25(OH) 2D 3 and adequate zinc. In summary, adequate dietary zinc concentration modulates the effects of vitamin D metabolites; also D 3 form has a greater anabolic effect on integrity of the bone than 1,25(OH) 2D 3. Furthermore, femur appears to be more sensitive than the other bones tested to changes in calcium concentration due to the two forms of vitamin D.

Assessment of zinc status in juvenile Atlantic salmon ( Salmo salar) by measurement of whole body and tissue levels of zinc

Duplicate groups of 40 g Atlantic salmon were fed dry pelleted diets based on cod muscle meal as a protein source for 8 weeks. The basal diet contained 17 mg Zn/kg to which 0, 10, 20, 40 or 80 mg Zn/kg diet, respectively, were added as ZnSO 4·7H 2O. After 8 weeks, 15 fish from each dietary treatment were marked and then they were fed the basal diet for another 4 weeks. Fish were sampled after 2, 4, 8 and 12 weeks. Blood samples were withdrawn and serum was analyzed for zinc concentration and alkaline phosphatase (AP) activity. Liver, kidney, vertebrae and intestine were removed from ten fish in each dietary treatment. A further ten fish were used for whole body mineral analyses. There were no significant differences in growth due to different dietary zinc concentrations and this, together with data on alkaline phosphatase and iron levels, showed that the basal diets contained sufficient zinc to prevent overt zinc deficiency symptoms. Zinc concentrations in the whole body and tissues, however, were significantly influenced by dietary zinc level. On the basis of the dietary zinc concentration required to maintain whole body zinc and serum zinc concentrations within the normal range, it was concluded that the dietary zinc requirement of juvenile Atlantic salmon is between 37 and 67 mg Zn/kg dry diet under our test conditions. Hence, until more data are available, juvenile Atlantic salmon diets based almost entirely on marine fish protein should contain > 67 mg Zn/kg dry diet.

Effects of dietary copper and zinc concentrations on feeding rates of two species of talitrid amphipods (Crustacea).

Effects of dietary copper and zinc concentrations on feeding rates of two species of talitrid amphipods (Crustacea).

Schätzung des zinkbedarfs für broiler anhand ihrer fähigkeit zur selektiven zinkaufnahme und mittels dosis‐wirkungs‐beziehungen

Broiler chicks are able to select an adequate dietary Zn-concentration in choice-feeding. The zinc requirement should be ascertained by this method of self-selection. 72 day-old chicks were divided into 9 groups and were kept over 5 weeks in individual cages. By gradually supplementing ZnSO4.7H2O to a semisynthetic basal diet with isolated soybean protein 5 diets were made with Zn-concentrations of 14, 22, 30, 38 and 50 ppm, which respectively were fed to one group. The four other groups had to choose between two rations: 14/38; 14/50; 22/38; 22/50. Selective zinc intake was represented by a significant increase of dietary zinc concentration compared to random selection (mean of both diets). Feed intake, zinc intake and weight gain were measured daily and the end total feed consumption, live weight, feed conversion rate, plasma-zinc concentration and plasma-zinc binding capacity at the end of the experiment. In comparison optimal dietary zinc levels were estimated by dose-response relations, both by sigmoid growth curves and by broken-line model. With 30 ppm Zn chickens reached a high fattening level with daily weight gains of 60 g. Feed intake and growth rate were markedly reduced at a dosage of 14 and 22 ppm Zn, feed conversion rate was tendentially decreased below a level of about 34 ppm, whereas above zinc binding capacity reached a plateau. Birds self-selected a dietary zinc level of 32 ppm, which were adequate for the criteria feed intake and weight gains. Zinc requirements of about 40 ppm were assessed by conventional methods.

Dietary Zinc Methionine Effect on Eggshell Quality of Hens Drinking Saline Water

In two experiments individually caged 60-wk-old laying hens were exposed to daily temperatures ranging between 18 and 35 C and given various dietary and drinking water treatments. In Experiment 1 these were: 1) basal diet and town water; 2) basal diet and town water supplemented with 2 g NaCl/L; 3) basal diet supplemented with .2 g zinc methionine (Zinpro-200)/kg diet and town water; or 4) basal diet supplemented with .2 g zinc methionine/kg and town water supplemented with 2 g NaCl/L. In Experiment 2, Treatments 1 and 2 were the same as in Experiment 1. Birds on Treatments 3 and 4 received the town water supplemented with 2 g NaCl/L and the basal diet supplemented with either .5 g zinc methionine/kg (Treatment 3) or .28 g ZnSO4 H2 O/kg to approximate the same dietary zinc concentration in Treatment 3 (Treatment 4). In both experiments, dietary zinc methionine plus 2 g NaCl/L in the drinking water significantly improved shell breaking strength over those birds on the 2 g NaCl/L with no zinc methionine supplementation. This same pattern occurred for shell weight, shell weight per unit of surface area, and percentage of shell defects. There were no improvements in the parameters measured from the supplementation of ZnSO4. The zinc methionine compound apparently was effective in overcoming the negative influence of the added 2 g NaCl/L of town water.

Toleration of High Concentrations of Dietary Zinc by Mink

Adult and kit male and female natural dark ranch mink (Mustela vison) were fed a conventional diet supplemented with 0, 500, 1,000, or 1,500 ppm zinc, as ZnSO4.7H2O, for 144 days. No marked adverse effects were observed in feed consumption, body weight gains, hematologic parameters, fur quality, or survival. Zinc concentrations in liver, kidney, and pancreas of the mink increased in direct proportion to the zinc content of the diet. Histopathologic examination of the livers, kidneys, and pancreata revealed no lesions indicative of zinc toxicosis. The results indicate that mink can tolerate at least 1,500 ppm dietary zinc, as ZnSO4.7H2O, for several months without apparent adverse effects.

The effect of various dietary zinc concentrations on the biological interactions of zinc, copper, and iron in rats

Three groups (14 rats each) were fed one of the following diets for 8 wks: a control purified basal diet containing 12 ppm zinc, 5 ppm copper, and 35 ppm iron; the basal diet with less than 2 ppm zinc; or the basal diet supplemented with 1000 ppm zinc. Rats fed the zinc-deficient diet had decreased weight gain, moderate polydipsia, and intermittent mild diarrhea. The zinc-supplemented rats had a cyclical pattern of food intake and weight loss from weeks 5 to 8. Tissue concentrations suggest that zinc and copper were not mutually antagonistic with chronic dietary imbalances. If tissue element concentrations reflected intestinal uptake, then competition and/or inhibition of intestinal uptake occurred between zinc and iron. The fluctuations in tissue element concentrations that occurred with increased duration of the study were at variance with previous studies of shorter time periods. The dietary proportions of zinc, copper, and iron appear to influence zinc, copper, and iron metabolism at the intestinal and cellular transport levels over a given period of time.

Effect of cis-diamminedichloroplatinum (II) on metallothionein induction and trace element metabolism in rats fed different amounts of dietary zinc

Recent studies have suggested that the induction of metallothionein synthesis in kidneys of mice by the acute administration of bismuth and other trace elements might protect against cis-diamminedichloroplatinum (II) nephrotoxicity. The present study was designed to determine the effects of dietary zinc and cis-diamminedichloroplatinum (II) on the induction of liver and kidney metallothionein and its subsequent effect on nephrotoxicity and trace element metabolism in rats. Male rats were fed diets containing 5, 20, 80, or 320 mg zinc/kg diet for 3 weeks. Each dietary group was subdivided into 3 groups. In one group, each rat received an i.p. injection of 7.5 mg cis-diamminedichloroplatinum (II)/kg b.w. All other rats received saline. During the next three days a second group of rats was pair-fed to the cis-diamminedichloroplatinum (II) injected group. A third group received no treatment and was allowed to eat ad libitum. Results showed that when dietary zinc was increased from 5 mg/kg diet to higher amounts, kidney metallothionein concentration increased twofold. cis-diamminedichloroplatinum (II) treatment increased kidney metallothionein even further, but elevated metallothionein gave no protection from the toxic effects of the drug. Serum copper concentration and ceruloplasmin activity were significantly lower with higher concentrations of dietary zinc, which indicated that these rats were mildly copper-deficient. There was a small but significant depression of superoxide dismutase activity and a highly significant increase in thiobarbituric acid reactive substances in kidneys of rats treated with cis-diamminedichloroplatinum (II) compared to either pair-fed or ad libitum controls. This supports the hypothesis that part of the mechanism for cis-diamminedichloroplatinum (II)-induced toxicity might be caused by free-radical generation. However, the data do not support the hypothesis that metallothionein induction protects the kidney from cis-diamminedichloroplatinum (II) toxicity.

Effect of dietary zinc on 65-ZN absorption and turnover in rats

The effect of zinc intake on retention, absorption, and biological half-life of 65-Zn was investigated using whole body counting after the carrier-free radioisotope was administered intragastrically or intramuscularly to 7-week old male rats. When animals consumed 7.8, 11.7, 16.0, 20.8, 36.8, 80.2, or 149.1 mg Zn/kg diet for 3 weeks before and 4 weeks after 65-Zn administration, the biological half-life and the retention of gavaged or injected 65-Zn were curvilinearly related to the dietary zinc concentration. Absorption was similarly affected, except that absorption was nearly 100 per cent at the two lowest levels of intake. Zinc concentrations in bone and serum were unaffected except in animals fed 7.8 mg Zn/kg diet. When zinc intakes varied only 4 days before 65-Zn administration, retention of injected 65-Zn and absorption were less affected. Animals fed 11.5 rather than 85.0 mg Zn/kg beginning 7 to 8 hours after 65-Zn administration, had greater retention of gavaged or injected 65-Zn; absorption and biological half-life of 65-Zn were also greater. Thus, retention of dietary zinc by the body depended on recent and subsequent zinc intake, with recent intake affecting mainly absorption, and subsequent intake affecting mainly excretion. Adjustments in absorption and excretion occurred within days, and were highly coordinated when zinc intakes exceeded the requirement.

Copper and zinc status in moderate alcohol intake.

To determine the effects of moderate alcohol (ETOH) consumption on dietary intakes, serum and urine zinc (Zn) and copper (Cu) concentrations (conc), groups of nonsmoking, moderate drinkers, non-athletes, healthy young adult males aged 21-35 years and within 10% of ideal body weight, consumed 40g of ETOH/day as beer (fixed group) or maintained normal drinking habits (variable group) for 6 weeks, and then abstained for 3 weeks. A similarly described group of non-alcohol drinkers served as the control. There was no alcohol effect on dietary Zn or Cu intakes, however, the control group had significantly higher intakes of Zn than the drinking groups. Cu intakes were the same in all groups. Generally, the serum Zn and Cu conc of the drinking groups only, markedly rose during ETOH consumption and fell during abstention. Although this trend was not observed in the control group, they had higher serum Zn and Cu conc than the drinking groups. In general, urine Zn conc remained constant from baseline to consumption period and then decreased during the abstention period in all groups studied. Results indicate that moderate ETOH consumption raised serum Zn and Cu conc but had no effect on dietary intakes of these minerals or on urine Zn levels.

Influence of Usual Zinc Intake and Zinc in a Meal on 65Zn Retention and Turnover in the Rat

The influences of zinc in a meal and usual zinc intake on zinc retention and turnover were investigated in 7-wk-old male rats fed diets containing 12–151 mg Zn/kg for 3 wk before and after consuming a 65Zn-labeled meal containing ZnCl2. Retention corrected to zero time and turnover rate were determined by whole-body counting. Percent zinc retention was inversely proportional to the natural logarithm of the meal zinc, between 0.09 and 26 µmol. In comparison to lower doses, higher doses resulted in lower percent retention but greater amounts of zinc retained. Although the latter relationship was slightly curvilinear, there was no indication of a limited capacity for zinc retention with high doses. However, doses above 4 µmol resulted in higher turnover rates in rats accustomed to lower zinc intakes. Percent retention and the reciprocal of the turnover rate were proportional to the reciprocal of the dietary zinc concentration. The greatest differences in retention and turnover occurred between 12 and 26 mg Zn/kg diet. The zinc dose in a meal and the usual dietary zinc separately influenced percent zinc retention. These factors also interacted, such that greater dose effects were observed at lower zinc intakes and greater dietary zinc effects were observed at lower doses.