Dietary Zinc Levels Research Articles

The Effects of High Dietary Zinc and Copper Deficiency on the Activity of Copper-Requiring Metalloenzymes in the Growing Rat

The effects of feeding rats high levels of dietary zinc (240 mg Zn/kg diet) on the activities of the copper-requiring metalloenzymes: ceruloplasmin (Cp), cupro-zinc superoxide dismutase (SOD) and cytochrome c oxidase (CCO) were determined. These were compared with those seen during copper deficiency (induced by feeding 0.6 mg Cu/kg diet). The activities of Cp in serum, Cu-Zn SOD in liver and heart, and CCO in heart were significantly reduced in both the high zinc and copper-deficient groups by 2 weeks, when compared to the activities seen in rats fed the control diet (6 mg Cu, 30 mg Zn/kg diet). In animals fed the high zinc diet, the reduction in heart CCO activity followed the decrease seen in heart copper concentration, whereas in blood and liver, the reductions in Cp and SOD activities, respectively, were greater than the reductions seen in copper concentration. Thus, the results of this experiment demonstrate that with high dietary zinc, the reductions seen in the activity of copper-requiring metalloenzymes were similar to those seen during copper deficiency.

Studies of marginal zinc deprivation in rhesus monkeys. I. Influence on pregnant dams

Rhesus monkeys were fed a diet marginally deficient in zinc (4 ppm zinc) throughout pregnancy and were monitored for changes in hematological, biochemical, and immunological parameters. This dietary zinc level was chosen because it did not produce an overt deficiency syndrome when fed for 10 wk to nonpregnant monkeys. Deprived animals were compared to control groups fed a zinc replete (100 ppm) diet ad libitum or on a food restricted (pair fed) basis. Beginning in the 3rd trimester zinc-deprived monkeys exhibited characteristic signs of deficiency including dermatitis, anorexia, and low levels of plasma zinc (less than 65 µg/100 ml) and of serum alkaline phosphatase activity. The extent of plasma zinc depression in deficient monkeys was dependent on total food intake; severely anorexic monkeys lost weight but maintained normal plasma zinc levels; monkeys that gained 20 to 30% of their body weight during pregnancy had severely depressed plasma zinc. Plasma vitamin A was reduced in the deprived group while copper, magnesium, and folate levels remained similar to controls. Hematological changes indicative of iron deficiency anemia (reduced packed cell volume, mean corpuscular volume, and Hb) were also seen in severely deficient monkeys. In addition, the peripheral lymphocyte mitogen response was reduced in deficient dams. We conclude that marginal deficiency of dietary zinc can produce significant abnormalities of nutritional status and has the potential for producing serious immunohematological dysfunction during pregnancy.

Reduced cadmium body burden in cadmium-exposed calves fed supplemental zinc

The objectives of this study were to evaluate the use of practical supplemental dietary zinc to modify the cadmium content in edible bovine tissues and to identify copper interactions with cadmium and zinc. The effect of supplemental zinc (200 or 600 μg/g) on the concentrations of cadmium, zinc, and copper in liver, kidney cortex, muscle, and blood of calves fed 50 μg/g cadmium for 60 days was evaluated. Blood samples were collected before and eight times after starting to feed cadmium or cadmium plus zinc. Liver, kidney, and muscle samples were collected when calves were slaughtered (baseline, at beginning of experimental feeding; cadmium-fed, at end of 60 days feeding). The cadmium concentrations of all sample types collected were markedly increased by the feeding of cadmium. Feeding 600 μg/g supplemental zinc significantly increased the zinc concentrations of liver, kidney cortex, and blood and decreased the cadmium accumulation in these organs as well as muscle. The copper concentrations of muscle or blood were not altered by feeding cadmium with or without zinc but those of liver and kidney cortex were significantly increased by higher dietary levels of zinc and cadmium. The potential use of dietary zinc salts in reducing cadmium body burden in food animals suspected or known to have high cadmium intakes is suggested.

Interaction of dietary zinc, genetic strain, and acetazolamide in teratogenesis in mice.

The effect of dietary zinc and genetic strain on acetazolamide-induced malformations was assessed. CBA (sensitive) and SWV (resistant) mice were fed purified diets containing five different levels of zinc throughout gestation and were given acetazolamide orally for a limited period during organogenesis. Controls received either no treatment or the drug vehicle. Litters were assessed for resorptions and malformations at term. The significance for influencing litter outcome was tested for the three main treatments: strain, dietary zinc level, and acetazolamide dose, plus their interactions. The magnitude of the litter response was strongly influenced by strain. The incidence of forelimb ectrodactyly, a characteristic malformation caused by acetazolamide, was much greater in CBA than in SWV fetuses. SWV fetuses had no ectrodactyly when dams were fed at least 9 micrograms/g zinc, but 5-8% showed ectrodactyly when dams received a zinc-deficient (0.4 or 4.5 micrograms/g) diet. The incidence of ectrodactyly in the CBA strain decreased as dietary zinc increased, but was still present when dams were fed a high (1,000 micrograms/g) zinc diet. The incidence of resorptions and total abnormal sites from litters of dams receiving acetazolamide decreased as dietary zinc increased, with the magnitude of the response being influenced by the strain. A significant (dietary zinc X acetazolamide) and (strain X acetazolamide) interaction was found for the ectrodactyly response. The results demonstrate the importance of considering interactions among genetic strain, diet, and drugs, as well as single factors as determinants of fetal risk.

Effect of Dietary Zinc and Protein Levels on the Utilization of Zinc and Copper by Adult Females

Zinc and copper utilization were examined in twenty-three young adult females fed either a moderate protein, low zinc diet, a high protein, low zinc diet, a moderate protein, high zinc diet, or a high protein, high zinc diet during a 24-day metabolic balance study. The moderate and high protein diets contained 7.9 g and 15.2 g nitrogen per day, respectively. The low and high levels of zinc were 9.5 or 10.1 and 18.4 or 19.9 mg daily. Copper intake was constant at approximately 2.0 mg/day. Urinary zinc excretion was significantly greater (P < 0.05) in subjects consuming the high protein diets. Fecal zinc paralleled zinc intake but was not affected by protein intake. Apparent retention of zinc was not significantly different among dietary treatments ranging from -0.29 to 1.58 mg/day. Fecal excretion and apparent retention of copper were not affected by protein intake. Mean copper retentions ranged from 0.12 to 0.30 mg/day. Dietary zinc did not affect copper excretion or retention. Dietary protein, at levels commonly consumed by a substantial portion of the American adult female population, did not affect zinc and copper utilization. Individuals were not consistently in positive balance although average retentions were generally positive.

Concentration of minerals in tissues of pigs from dams fed different levels of dietary zinc.

Effects on the tissue mineral concentrations of pigs from sows fed four dietary Zn levels were studied. A male and a female from first- and second-parity litters were killed at 1 and 21 d of age. The dams were fed a corn-soybean meal basal diet supplemented with 0, 50, 500 or 5,000 ppm Zn from 30 kg body weight until completion of the second lactation. Pigs from sows fed 5,000 ppm additional zinc had heavier liver, heart, thyroid and adrenal weights relative to their body weight than did pigs from sows on the other treatments. First- and second-parity pigs from sows on the highest Zn supplementation level had higher Fe stores in the liver, higher Zn concentrations in the liver, kidney and pancrease, and higher Cu levels in the kidney compared with pigs from sows on the other treatments. However, Cu concentrations in the liver, heart, pancreas, esophagus, aorta and testes were reduced in pigs from sows on the 5,000 ppm Zn treatment. In first-parity pigs, Ca in the liver was higher for pigs whose dams received 5,000 ppm Zn compared with pigs from sows on all other treatments, and the Mn level was higher compared with pigs from sows receiving 50 or 500 ppm additional zinc. Pigs at 1 d of age from sows on the 0, 50 or 500 ppm treatment had lower hepatic P and Zn concentrations than pigs from sows on the same treatment at 21 d of age. The reverse was true for pigs whose dams received 5,000 ppm Zn.

High Zinc Supplementation of Rainbow Trout Diets

Abstract Zinc in the form of zinc sulfate or chelated as zinc proteinate was fed in increasing levels (4 to 1,700 µg/g zinc) in an egg-white based diet to fingerling rainbow trout (Salmo gairdneri) to determine potential toxicity. Zinc sulfate was fed for the first 55 days and zinc proteinate for the last 118 days of a 173-day test. Fish fed the lowest level of zinc (4 µg/g zinc, a zinc-deficient diet) had poor growth and high mortalities, while the lowest level of added zinc (90 µg/g) reduced mortalities and markedly improved growth. Higher levels of supplemented zinc, up to 1,700 µg/g, had no further effect on growth or survival. Zinc concentration in liver, blood, and gills increased with dietary levels of zinc above 90 µg/g. Trout showed no signs of zinc toxicity during feeding with levels of dietary zinc as high as 1,700 µg/g.

The Effect of Interactions between Dietary Egg White Protein and Zinc on Body Weight, Bone Growth and Tissue Trace Metals in the 30-Day-Old Rat

Nine groups of 30-day-old rats were fed different diets, which contained 8, 15 or 20% egg white (equivalent to 6.0, 11.3 and 15.0% protein, respectively) each at 3 levels of zinc (6, 12 and 18 ppm zinc) for 30 days. The rats consuming the 6.0% protein, regardless of zinc intake, gained less weight than the groups fed 11.3 or 15.0% protein. Plasma zinc was not influenced by dietary egg white protein content, whereas, plasma zinc levels were lower in the rats fed 6 ppm dietary zinc compared to those fed 12 or 18 ppm zinc. Of the liver trace metals measured, only iron appeared to be influenced by an egg white protein-zinc interaction. Increasing dietary egg white protein led to increased concentrations of liver zinc and magnesium. Dietary zinc levels had no effect on the concentration of these metals in the liver. Liver calcium and copper concentrations were not significantly influenced by either dietary zinc or egg white protein. Femur weights and lengths were lower in the rats fed 6.0% than in those fed 11.3 or 15.0% protein diet but were unaffected by dietary zinc. Femur width was related to dietary protein and zinc. Dietary protein and zinc were interrelated in their affect on femur zinc levels. Femur zinc concentrations increased with increasing dietary zinc levels. Also femur zinc levels decreased with increasing dietary protein content. Other femur metal (copper, iron and calcium) concentrations were higher in rats fed the low level versus the higher levels of protein, but were not influenced by dietary zinc. These results show that dietary zinc and egg white protein are interrelated with regard to their effect on body and femur growth and tissue trace metal content.

Effect of dietary zinc levels on the growth and development of the gilt.

The effect of dietary Zn levels on the growth and development of gilts was studied. Sixty crossbred and purebred Yorkshire gilts weighing about 30 kg were allotted by sire into four treatment groups and blocked by the date they were farrowed into three blocks. The dietary treatments, which were the amounts of Zn from Zn0 added to the diet, were 0, 50, 500 and 5,000 ppm. Thus, the treatments were less than NRC nutrient requirement, equal to the NRC requirement, 10 times requirement and 100 times requirement for Zn added to a basal corn-soybean meal diet. Weight gain and feed efficiency were not affected by dietary treatment, although there was a trend for gilts receiving 5,000 ppm added Zn to weigh less after 20 wk. After 4 wk on the experimental diets, gilts receiving 5,000 ppm supplemental Zn had elevated serum alkaline phosphatase (SAP) activity and serum Zn levels. The activity of SAP tended to decline with age for animals receiving the other dietary treatments. Gilts receiving no supplementary Zn or 50 ppm additional Zn tended to have lower serum Zn concentrations at 4, 12 and 20 wk on the study than initially. Copper concentrations in the serum were reduced when gilts were fed 5,000 ppm additional Zn. These results suggest that gilts tolerate 5,000 ppm supplemental Zn from Zn0 during growth and development, but mineral profiles are altered.

Effect of dietary zinc levels on mineral concentration in milk.

Effects of supplemental dietary Zn levels of 0, 50, 500 and 5,000 ppm on the mineral concentration in milk of first- and second-parity sows were evaluated. Colostrum from sows fed 5,000 ppm of supplemental Zn contained less Cu and P than colostrum from sows on the other treatments. Calcium was reduced in the colostrum from sows fed 0 or 5,000 ppm Zn. Copper was reduced and Zn increased in milk from sows fed the highest Zn level compared with the other treatments during wk 1, 2 and 3 of lactation. Iron was lower in the 2nd wk milk from sows supplemented with 50 ppm Zn compared with sows on the other treatments. Copper and Zn concentrations were reduced in the 1st, 2nd and 3rd wk milk from sows fed 0, 50 or 500 ppm additional Zn compared with colostrum, but only Zn was reduced in milk from sows supplemented with 5,000 ppm Zn compared with colostrum. Calcium concentrations were increased in milk for all treatments compared with colostrum, and Mg was increased in 1st, 2nd and 3rd wk milk from sows fed 0, 50 or 500 ppm Zn and in 2nd and 3rd wk milk from sows fed 5,000 ppm Zn compared with colostrum. Phosphorus was higher in 2nd wk milk from sows fed 0 or 500 ppm Zn and higher in 3rd wk milk for sows fed 0, 500 or 5,000 ppm Zn compared with colostrum. The Fe concentration in 1st wk milk from the second-parity sows was increased compared with that from the first-parity sows for all treatments. Magnesium was reduced in second-parity colostrum compared with first parity for all treatments except the unsupplemented group.

Effect of dietary calcium and zinc levels on weight gain and blood and tissue mineral concentrations of growing Columbia- and Suffolk-sired lambs.

One hundred and sixty Columbia- and Suffolk-cross intact male and female growing lambs (8 wk of age) were used in an 84-d feeding trial to determine the effect of two levels dietary Ca and Zn on weight gain, feed utilization and several blood and tissue traits. Two levels of Ca (.5 and .8%) and two levels of Zn (20 and 100 ppm) were fed in a 2 X 2 factorial arrangement of dietary treatments. There was no effect of diet on performance or on blood traits. Columbia lambs had heavier fleeces at slaughter than Suffolks (P less than .01) and males had heavier fleeces than females (P less than .01). Based on the similarity in performance among lambs fed the four diets differing in Ca and Zn level, it is concluded that a dietary Ca level of .5% and a Zn level of 19 to 26 ppm is adequate for normal weight gain, feed utilization, liver and humerus ash concentrations and blood plasma concentrations of Ca, P, Zn, total protein, albumin, alkaline phosphatase and blood hemoglobin and hematocrit. Further, it appears that an elevated level of dietary Ca does not precipitate a clinical Zn deficiency in the growing lamb, in contrast to the general observation in growing swine.

A Copper Deficiency in Neonatal Pigs Induced by a High Zinc Maternal Diet

Because high levels of dietary zinc are known to reduce copper body stores, the objective was to determine if a high zinc maternal diet could induce a copper deficiency in the newborn pig fed a dried skim milk-glucose-starch diet unsupplemented with copper. The offspring of gilts, which were fed 5000 ppm of zinc, were allowed to nurse until 3 to 5 days of age when they were weaned and placed in individual stainless-steel pens. The dietary treatments were 0, 5 and 10 ppm added copper from copper sulfate. After 14 days, pigs receiving the 0-ppm copper diet weighed significantly less (P < 0.05) and had reduced hemoglobin, hematocrit and serum copper concentrations and no detectable ceruloplasmin activity. After 5 weeks, the pigs were killed, and tissues were collected. The unsupplemented group had 16.4% of the aortic lysyl oxidase activity of the 5-ppm group. Cytochrome c oxidase activity in the heart and liver, and copper stores in the heart, liver, pancreas and kidney were depressed (P < 0.05) in unsupplemented pigs compared to those receiving 5 ppm copper. These data demonstrate that it is possible to produce quickly a markedly copper-deficient pig, by using the offspring of sows fed 5000 ppm zinc, and support previous conclusions that the dietary copper requirement of the baby pig is about 5 ppm.

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The effect of zinc on the growth of a transplantable DAB hepatoma in young male Wistar rats was determined. Both a zinc deficiency (less than 0.5 microgram/g feed) as well as high levels of dietary zinc (500 micrograms/g feed) significantly reduced tumor growth. Both high- and low-zinc diets resulted in reduced activity of the salvage pathway of thymidine synthesis as well as reduced 32PO4 incorporation into DNA and diminished DNA polymerase activity. Blockage of the de novo pathway of DNA synthesis by the folate antagonist methotrexate (MTX) resulted in greatly increased flux through the thymidine salvage pathway and increased DNA polymerase activity but decreased 32PO4 incorporation in the transplantable hepatomas in Wistar rats fed normal zinc diets (50 micrograms/g feed). MTX had the effect of reducing all these activities in the groups fed low- and high-zinc diets. These data suggested a site of action of zinc associated with the salvage pathway of thymidine synthesis.

Iranian Flat Breads: Relative Bioavailability of Zinc

ABSTRACTThe effect of flour extraction rate, type and length of fermentation and baking conditions on relative bioavailability of zinc of five distinctly different Iranian flat breads and their unfermented doughs, was determined using weanling rats fed low (5.5 ppm) levels of dietary zinc. When breads rather than unfermented doughs were used for preparation of diets, with one exception, bioavailability of Zn significantly (P &lt; 0.05) improved. Rats on the barbari‐bread‐based diet showed the highest weight gain and femur zinc content. There was no significant difference in weight gain among rats on dough‐based diets. High correlation of weight gain and femur zinc with feed intake and low or no correlation with fiber or Zn:phytate molar ratio of the diets was observed.

Effects of Maternal Dietary Zinc on Growth and Mitogenic Responsiveness in Suckling Mice

The effects of varied levels of maternal dietary zinc on growth and immunological development of suckling A/J mice were studied. From 5 days postpartum, lactating dams were fed biotin-fortified egg-white diets containing the following levels of zinc: 1.6 µg/g (low zinc), 3.6 µg/g (intermediate zinc), 5.8 µg/g (moderate zinc) and 30 µg/g (control). At 17 days of age, low zinc pups exhibited reduced body weight gain (70%), smaller thymuses and spleens, and reduced splenocyte numbers (18%). Intermediate zinc pups had normal body weights but slightly reduced spleens and thymuses; moderate zinc pups were unaffected. Since suckling mice are not fully immunocompetent, splenic mitogenic responses to phytohemagglutinin (PHA), concanavalin A (Con A), lipopolysaccharide (LPS), pokeweed mitogen (PWM), and dextran sulfate (Dx) were used to evaluate the status of various lymphocyte subpopulations. Neonates from the low zinc group gave no Con A response and limited responses to LPS and PWM (50%). Intermediate zinc pups responded satisfactorily to all mitogens except LPS (64%); moderate zinc pups responded normally. It was concluded that 5.8 µg/g maternal dietary zinc, fed day 5–17 postpartum, is adequate for normal neonatal growth and mitogenic responses. Conversely, 1.6 µg Zn/g caused neonatal growth retardation and reduced mitogenic responses without excessive mortality.zinc deficiency suckling mouse neonates mitogens immune development

The Effect of Severe Protein Deficiency on Serum Zinc Concentration of Mice Fed a Requirement Level or a Very High Level of Dietary Zinc

The objective of the present study was to determine the effect of severe dietary protein deficiency on serum zinc concentration in weanling animals fed either a requirement level or a very high level of dietary zinc. Weanling (21-day-old) male and female CBA/J mice were randomly assigned to be fed one of four diets containing either 1.7% or approximately 18.5% protein and either 7 µg (predetermined requirement level) or about 200 µg zinc per gram of formulation. Serum zinc levels were measured after a 14-day feeding period. Dietary zinc content, over the range tested, did not influence the serum zinc level of protein deficient mice, and these animals exhibited serum zinc concentrations which were much lower than the levels found in adequately nourished mice fed the requirement level of zinc (7 µg/g diet). These results indicate that dietary zinc supplementation is unable to restore to normal the zinc status of severely protein-deficient animals. This may be an important factor to consider when studying the effect of protein deficiency on zinc-sensitive physiological processes.protein deficiency zinc mice

Effects of moderate zinc deficiency on cognitive performance in young adult rats

Two experiments were conducted to establish a dietary zinc level which approximates a moderate deficiency in the young adult rat and to determine if a concurrent zinc deficiency affects cognitive performance. Male rats were fed varying levels of zinc in diet throughout a 17-day period. The lowest dietary level that depressed serum and bone zinc without influencing food consumption or body weight gains was observed to be 5.8 μg Zn/g diet. Young adult rats maintained on either a zinc adequate (24.4 μg Zn/g) or low-zinc (5.3 μg Zn/g) diet were tested in a modified Skinner Box involving tests of visual, auditory, association, and discrimination learning. No differences were observed in the visual discrimination performance of the zinc deficient animals when compared with control counterparts. Deficits in the ability to transfer a learned association between visual and auditory stimuli were observed, however, in the deficient group during the transfer test phase. The latter performed better during the final auditory discrimination task in transferring a learned food-relevant cue.

Ovine and Bovine Metallothioneins: Purification, Number of Species, Zinc Content and Amino Acid Composition

Metallothioneins (MTs) were purified with respect to zinc from tissues of cattle and sheep which had been fed high levels of dietary zinc. These proteins were purified by gel filtration (Sephadex G-75), ion exchange chromatography (twice on DEAE Sephacel) and gel filtration again (Bio-Gel P-10). There is one major and up to three minor MT species in liver, kidney and pancreas from both sheep and cattle. The amount of zinc varies between the different species of MT. Amino acid analyses of the purified preparations revealed a cysteine content of up to 35.7% and the absence of aromatic amino acids for the major species, but the minor proteins contained less cysteine and some aromatic amino acids. The significance of MT in zinc metabolism is discussed.metallothionein ovine bovine

Effect of vegetarianism on the zinc status of pregnant women

The zinc status of 12 pregnant vegetarian women, six pregnant nonvegetarian women, and five nonpregnant vegetarian women was evaluated. Zinc intake was calculated from 3-day dietary records. Hair, urinary, and nonfasting plasma samples were collected during an interview. Dietary, plasma, urinary, and hair zinc levels did not differ significantly between the pregnant vegetarians and nonvegetarians. But plasma zinc was about 21% lower in the pregnant women than the nonpregnant women even though the pregnant women consumed about twice as much zinc as the nonpregnant women. The data suggest that the parameters of zinc status studied were affected by pregnancy more than ovo-lacto vegetarian dietary habits.

Effects of Dietary Zinc Levels on Zinc Concentrations in Tissues of Common Carp

Common carp always has higher zinc concentration in viscera than other carps. To determine the relationship between the dietary zinc level and zinc concentration in common carp, the fish were fed diets containing 17, 294, 1,007 and 1,974 ppm zinc for 8 weeks, and the zinc concentration in each tissue was measured. It was found that the group of fish fed 17 ppm zinc had the highest growth rate. When the dietary concentration of zinc was lower than 294 ppm, the zinc concentrations in the tissues were similar during the 8 weeks of experiment. The zinc accumulated in the fish when the dietary zinc concentration was higher than 1,007 ppm. Zinc accumulated first in the digestive tract, then in the skeletal tissues and then in skin and muscle. Common carp and silver carp were fed the same diet from hatchling till adult. The results indicated that no matter whether the feed was natural food or artificial feed containing 300 ppm of zinc or artificial feed containing 25 ppm of zinc, the zinc concentrations in common carp were several times higher than silver carp. We concluded that the fact that common carp had higher zinc concentrations than other carps was not caused by the diet, but might arise from the fact that the absorption rate of zinc was higher.zinc carp