Effects Of Dietary Molybdenum Research Articles

Effects of dietary molybdenum, sulfur and zinc on the excretion and tissue accumulation of trace elements in sheep fed palm kernel cake-based diets

Twelve male 8-month-old lambs were used in a 6-month feeding experiment to determine the effects of dietary Mo, Mo + S and Zn supplements on the body retention and tissue accumulation of dietary Cu, Zn and Fe. The lambs were divided into four groups of three lambs each and each group was fed ad libitum one of four diets. A control diet was based on palm kernel cake (PKC) and grass hay. Three additional diets were the control supplemented with either Mo or Mo + S or Zn. At 3 months of the experiment, feces and urine were collected and sampled for 6 days. At the end of the experiment (6 months), blood was sampled and then the sheep were slaughtered. The liver and kidney were removed and sampled for chemical analysis. In comparison with the control, each dietary supplement decreased (P < 0.05) the Cu concentration in the liver, but only the Mo + S supplement decreased it to a safe range of below 350 μg/g dry matter. This was accompanied by the body retention of dietary Cu of 24.6%, 6.7%, 2.5% and 6.5% for the control, Mo, Mo + S and Zn treatments, respectively. The blood plasma concentration of Cu was decreased (P < 0.05) by the Zn supplement, but was not affected by other supplements (P > 0.05). It was concluded that from the supplements tested, only Mo + S appeared to be effective in reducing the retention and liver accumulation of the dietary Cu to prevent chronic Cu toxicity in sheep fed PKC-based diets.

The effect of dietary molybdenum or iron on copper status and trace element accumulation in the pituitary and ovary of growing lambs

Secondary copper deficiency in ruminant animals is induced by high dietary levels of molybdenum (Mo), iron (Fe) or sulphur (S). Within the rumen, sulphur reacts with Mo to form a series of thiomolybdate molecules (TM) which may chelate copper. This reduces copper absorption or if TM is absorbed, inhibits copper metallo-enzyme activities. Parental administration of TM has resulted in an increase in Cu to the brain and an increase in Mo to the pituitaries (Haywood et al., 1998). This redistribution may alter neurological, endocrine and reproductive function. However, there are no reports on effects of endogenously produced TM on brain or pituitary trace element accumulation. The objective of this study was to determine the effect of dietary Mo or Fe on copper status and mineral retention in the pituitary gland and ovary of growing lambs.

The effect of dietary molybdenum and sulphate on sexual activity and plasma progesterone concentrations of ewes

The effect of an induced copper (Cu) deficiency on the fertility of South Africa Mutton Merino ewes ( Ovis aries) was investigated. The incidence of oestrus of adult ewes suffering from an induced Cu deficiency by supplementing molybdenum (Mo – 38 mg Mo/kg feed) and sulphur (S – 0.34%) to their diet was compared to that of a control group (Mo – 1.3 mg/kg; S – 0.22%). Although no significant differences in plasma progesterone concentrations were recorded during the oestrus cycles, 75% of the four-to-six-tooth experimental ewes (Cu deficient) stopped showing signs of behavioral oestrus (silent heats) after 6 weeks on the diets (middle May). In Trial 2, 5-month-old ewes ( n = 13) reaching puberty were used. The effects of an induced Cu deficiency on plasma progesterone concentrations, shortly after reaching puberty, were investigated. According to the plasma progesterone concentrations during the oestrus cycle, Cu deficiency resulted in ewes going into a state of anoestrus approximately 2–4 weeks earlier (May–June) at the end of the active breeding season. Although the older ewes (four-to-six-tooth) still ovulated they did not show any signs of oestrus compared to the younger ewes which stopped ovulating.

The effect of dietary molybdenum and sulphate on the oestrus cycle and ovulation in ewes after manipulation with exogenous progesterone alone or in combination with FSH and LH

Sixteen adult South African Mutton Merino ewes ( Ovis aries) were divided in two groups. The diet of the experimental animals was supplemented with molybdenum (Mo: 38 mg/kg feed) and sulphur (S: 0.34%) to induce a secondary copper deficiency. Two trials were conducted with four control and four experimental animals in each trial. After synchronisation with progesterone sponges during Trial 1, all the control ewes showed behavioural oestrus with subsequent corresponding ovarian and hormonal reactions. Only one of the experimental ewes showed signs of oestrus. During Trial 2, the ewes were superovulated using progesterone sponges and e-FSH. All control ewes showed signs of behavioural oestrus as opposed to 50% of the experimental animals. The ovarian weight (g) (3.52 ± 0.89 versus 1.50 ± 0.57) and number of follicles (7.52 ± 7.35 versus 14.5 ± 4.93) were reduced ( p < 0.05) compared to the control animals. According to the hormonal profiles the progesterone, FSH and LH concentrations were lower ( p < 0.05) in ewes suffering from a Cu deficiency compared to control animals. It is suggested that a Mo and S induced Cu deficiency inhibits GnRH release or the production of FSH and/or LH to such an extent that cyclicity in the ewe is suppressed.

Effect of dietary Molybdenum content and floor type on the liver copper concentration at slaughter and Iamb growth rate of early weaned lambs

The accumulation of copper (Cu) in the liver of intensively fed sheep, resulting in sub-clinical organ damage and eventually death due to Cu poisoning, is an important constraint on intensive animal production. Previous studies have demonstrated the antagonistic effect of dietary molybdenum (Mo) on Cu absorption in the ruminant (Suttle, 1991). The role of rumen ciliate protozoa in the breakdown of soluble protein and liberation of sulphide, also a Cu antagonist, and the reporting of a number of cases of chronic Cu poisoning in defaunated animals suggests that the state of the rumen microbial population may also have an effect on the absorption of dietary Cu. The aim of this experiment was to assess the effect of adding Mo to the diet and the availability of straw bedding, (through its effect on rumen environment and microbial population), on the liver Cu concentration at slaughter of early weaned lambs finished intensively on an all concentrate diet.

Effects of dietary molybdenum on nematode and host during Trichostrongylus vitrinus infection in lambs

The addition of molybdenum (0·05 mmol kg −1 dry matter) to the diet of lambs exposed for four weeks to a trickle (2500 third stage larvae per day) infection with Trichostrongylus vitrinus reduced the number and length of adult worms retrieved from the small intestine 11 days later: both effects were particularly marked in female worms from female lambs (P < 0·001). Worms from lambs given molybdenum contained less proteinase enzyme activity and secreted less proteinases in culture irrespective of the sex of the host. Pathogenicity was not attenuated by molybdenum. Damage to the intestinal mucosa was severe in both dietary groups but infected females given molybdenum developed lower plasma albumin concentrations and lighter dressed carcases than those not given molybdenum. Neither the effects on the parasite nor those on the host could be attributed simply to molybdenum-induced copper depletion, using conventional measures of copper status. Molybdenum may be toxic to T vitrinus but may also facilitate or enhance the inflammatory process limiting larval establishment] or increasing parasite rejection.

Effects of dietary molybdenum on nematode and host during Haemonchus contortus infection in lambs

The addition of molybdenum (0·05 mmol kg −1 drymatter) to the diet of lambs given a trickle infection of Haemonchus contortus larvae (500 third stage larvae d −1 over six weeks) reduced mean faecal egg counts (epg) from 3952 to 2312 ± 402 by 32 days (P < 0·02) and greatly reduced the mean number of worms recovered from the abomasum 14 days after infection ceased (907 compared with 4167: P < 0·01). Infection reduced haemoglobin concentrations less in lambs given molybdenum although the difference was small relative to the reduction in worm burden. Lambs not given molybdenum had low intraepithelial mast cell counts in the abomasal mucosa and less abomasal hypertrophy than expected from abomasal parasitism. Molybdenum did not consistently reduce the copper status of the host or the parasite. Previous exposure to molybdenum greatly reduced protein but not proteinase activity in, or secreted by, adult worms cultured for eight hours. It is suggested that molybdenum either increased the inflammatory response which preceded worm rejection or that it indirectly enhanced that reaction by reducing the effectiveness of copper-dependent, anti-inflammatory enzymes in the gastrointestinal mucosa.

The effect of dietary molybdenum and iron on copper status and growth in cattle

SummaryThe effects of supplementation of a barley-barley straw diet containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 mg iron (Fe)/kg D.M. on the Cu status, growth and clinical condition of calves are described. Liver and plasma Cu concentrations declined rapidly within 12–16 weeks to levels indicating severe Cu deficiency in both the Mo- and Fe-supplemented groups. The changes in Cu status were similar for both supplements and did not differ significantly from each other. Clinical signs of Cu deficiency, as indicated by reduced growth rate and changes in hair texture and colour, were evident after 16–20 weeks only in animals on the Mosupplemented diet. The reduced growth rate was accompanied by a decreased food intake and reduced efficiency of food utilization. The Mo-supplemented animals also exhibited an altered Fe metabolism, particularly when the growth rate was affected. The results confirm earlier reports that the effects of Mo on growth and clinical condition are independent of its effect on Cu status and suggest that the altered production might be due to effects on the control of food intake, food utilization, or Fe metabolism.

The effect of dietary molybdenum and iron on copper status, puberty, fertility and oestrous cycles in cattle

SummaryTwo experiments were conducted to examine the effects of supplementation of a control diet of barley grain and barley straw containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 or 800 mg iron (Fe)/kg D.M. on puberty, fertility and oestrous cycles of cattle. Puberty occurred normally in control, Fesupplemented and control animals on a restricted intake whereas it was delayed by 12 and 8 weeks respectively by Mo supplementation. This effect of Mo was not due to the low Cu status since this was equally low in the Fe-supplemented animals, nor was it due to the reduced growth rate since puberty occurred normally in control animals that had a similar live-weight gain. A significant reduction in the pulsatile release of luteinizing hormone was observed within 11 weeks of the Mo supplementation and before any of the other clinical signs were evident, suggesting that Mo may be affecting puberty by altering the release of luteinizing hormone either directly or indirectly.Mo supplementation significantly reduced the percentage conception rate to 12–33% compared with 57–80% in control and Fe-supplemented animals. This effect was not dependent on the rate of live-weight gain which was standardized across the different treatments at approximately 0·6 kg/day. Within 12 weeks of the replacement of dietary Fe by Mo a lower conception rate occurred; replacing dietary Mo by Fe led to a normal conception rate within 12 weeks without any accompanying changes in Cu status or in the rate of live-weight gain. The plasma Mo concentrations, however, changed significantly during these alterations in dietary supplementation. The pre-ovulatory peak height of luteinizing hormone was significantly lower in animals on the Mo-supplemented diet compared with control and Fe-supplemented animals, but the administration of LHRH did not alter the conception rate.More Mo-supplemented animals failed to ovulate following prostaglandin induced synchronization in comparison with the other treatments, and by the 84th week a significantly greater number of Mo-supplemented animals (12/18) had become anoestrous compared with the other groups (2/30). Cu repletion of these anoestrous Mo animals for a period of 20 weeks did not result in resumption of normal oestrous cycles, but ovulation and oestrus were induced by progesterone and LHRH treatment. Results in the latter part of the study indicated that Mo caused superovulation.These data show that Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain. It is suggested that these effects of Mo are associated with a decreased release of luteinizing hormone that might be due to an altered ovarian steroid secretion.

Effects of dietary molybdenum and sulphur on the distribution of copper in plasma and kidneys of sheep.

1. A 30-week study has been made in growing ewe lambs of the effects of dietary supplementation with molybdenum, or Mo plus inorganic sulphate on the distribution of copper in their blood plasma and kidneys. 2. The addition of 25 mg Mo and 5 g SO42-/kg diet increased Cu concentrations in plasma and kidney and decreased those in liver. Plasma caeruloplasmin activities (ferroxidase; EC 1.16.3.1) were unaffected. 3. Subcellular fractionation of the kidney cortex and gel filtration of the plasma and kidney cortex cytosol showed that the increased Cu content of these tissues was associated with abnormalities in the distribution of Cu. It appeared that both Cu and Mo were associated with the same proteins. 4. Dietary supplementation with Mo alone (25 mg/kg) had no effect on plasma or kidney Cu concentrations, suggesting that S metabolism is involved in the formation of the abnormal Cu-binding proteins in plasma and kidney. 5. The results are discussed in relation to the induction of Mo-induced Cu-deficiency states and the possible involvement of thiomolybdates.

Effects of dietary molybdenum on the metabolism of copper and molybdenum in young cattle

On separate occasions young cattle were injected intrarumenally with 99Mo or 64Cu or intravenously with 64Cu. The metabolism of the isotopes were compared to evaluate metabolic changes associated with molybdenum-induced copper deficiency. Molybdenum-99 metabolism was the same in both controls and experimental subjects. Marked differences in plasma kinetics were observed following intrarumenal 64Cu injection, with experimental animals displaying earlier plasma appearance and maintaining higher plasma levels than did controls. Similarly, higher plasma levels, more rapid plasma reappearance and greater fecal excretion were observed following intravenous injection of 64Cu in the experimental animals than in controls. A mechanism involving abnormal ceruloplasmin synthesis associated with the molybdenum-copper interaction is proposed.

Copper: Molybdenum interaction: Effect of dietary molybdenum on the binding of copper to plasma proteins in sheep

Four groups of three Blackface wethers were fed diets adequate in copper and supplemented with 0, 8, 16 or 24 μg./g. molybdenum for 203 days. All animals were then fed the unsupplemented diet for a further 21 days and blood samples were taken at intervals throughout. Sheep receiving Mo supplements up to 8 μg./g. showed no changes in plasma Cu distribution. By contrast, diets containing 16 and 24 μg./g. added Mo produced considerable changes in plasma Cu distribution, but the extent of the changes were similar for both diets. The changes produced by the diets were complete within about 12 days and when the dietary Mo supplement was withdrawn the changes were reversed in a similar period. The two higher levels of Mo supplementation produced the following changes: an increase in total plasma Cu and direct reacting Cu, no change in absolute concentration of caeruloplasmin Cu, but a decrease as a proportion of total plasma Cu. In addition it was shown that about a third of the plasma Cu was insoluble in TCA and that some of this fraction appeared to be estimated as direct reacting Cu. The significance of these findings in relation to the current concepts of the distribution of Cu within plasma and of the mechanisms of interaction of Cu and Mo is discussed.

The effect of dietary molybdenum on hypocupraemic ewes treated by subcutaneous copper.

An attempt has been made to assess the importance of systemic sites of interaction from the effect of dietary molybdenum (Mo) on the protection afforded by a single sc injection of copper (Cu) to 29 initially hypocupraemic 5-year-old ewes, maintained on a low Cu diet. They were fed a diet of 1 kg/day containing 1.3 mg of Cu/kg supplemented with sodium sulphate which provided 1.7 gm of sodium per kg. Group A was given no further supplement. Group B was given added Mo, 25 mg/kg. Group C was given added Cu, 10 mg/kg. After 7 months, several animals in each group were injected sc with a single dose of 46.5 mg of Cu in the form of copper calcium edetate (Coprin). Blood samples were taken at intervals from the injected ewes over a 250-day period. All ewes were mated after 12 months on the diet. Injected ewes were approaching the 4th month of gestation when the last blood sample was taken at 250 days. Total Cu in plasma was determined by atomic absorption spectometry. Direct reacting Cu in plasma, cerulosplasmin oxidase activity, and hemoglobin were also estimated. Plasma Cu concentrations had increased to normal levels in 14 days in Group A after the Cu injections. Group B animals showed a greater increase, mean values exceeding those of Groups A and C, between Days 28-129 (p less than .01). Plasma Cu levels declined in ewes not given supplementary Cu after the 177th day. The final values for Groups A and B were similar to those found before injection. The direct reacting Cu in each group was increased after 7 days (p less than .05). This effect was most marked in the Mo supplemented ewes (Group B). The effect of Mo persisted until the final bleeding. Direct reacting Cu was only a minor part of the early response in total plasma copper of Group B ewes. Dietary Mo did not inhibit the incorporation of injected Cu into ceruloplasmin. The Mo-supplemented ewes were in poorer condition than copper-supplemented ewes. All groups gained in weight after the injections. The sc injection of Cu at 5 months prior to mating imporved fertility in Groups A and B. There was no evidence that dietary Mo impa ired the metabolism of parenteral Cu. However, it is known to deplete r uminants of Cu when the diet provides the only source of Cu. It is ther efore thought that the site of the Cu with Mo interaction is in the gut. If infertility due to Cu deficiency is suspected in a flock, an injection of Cu immediately prior to mating may improve conception rate and provide sufficient Cu to reduce the incidence of swayback.

Effect of Dietary Molybdenum and Sulfate upon Urinary Excretion of Copper in Sheep ,

The effects of 0.4% sulfate alone and in combination with 50 ppm of dietary molybdenum, upon kidney level and urinary excretion of both radiocopper and stable copper were studied in sheep. All data indicated that the addition of molybdenum plus inorganic sulfate to the diet resulted in greater accumulation of copper in the kidney and its increased excretion by way of the urine. Urine volume was increased greatly when molybdenum plus inorganic sulfate was added to the diet and the increased filtration in the kidney may have contributed to the increased urinary copper. Supplemental inorganic sulfate alone had no effect upon those parameters of copper metabolism which were studied.

Effect of Dietary Molybdenum and Sulfate upon Copper Metabolism in Sheep

The effects of 0.4% dietary inorganic sulfate, or a combination of 50 ppm molybdenum plus 0.4% sulfate, upon plasma clearance of intravenously injected 64Cu, and its uptake by the liver and incorporation into ceruloplasmin, were studied in Florida native sheep. When both sulfate and molybdenum were present in the diet, a reduced uptake of radiocopper by the liver and an impairment in its utilization for ceruloplasmin synthesis occurred. This resulted in a slower removal of radio-copper from the plasma. Stable copper in the liver and in the ceruloplasmin fraction of plasma was significantly reduced in the sheep receiving both sulfate and molybdenum. All data indicated a metabolic interference with copper by sulfate and molybdenum in the liver. As a tentative explanation of the mechanism of this interference, either an impairment of copper uptake by liver cells, or a primary intracellular metabolic disturbance in the synthesis of copper-protein compounds including ceruloplasmin, or both, are postulated. Dietary inorganic sulfate, in the absence of supplemental molybdenum had no effect upon the parameters of copper metabolism studied.

The effect of molybdenum on ascorbic acid metabolism in rats.

1. The effect of dietary molybdenum on the growth rate and also on ascorbic acid metabolism in rats was studied. An excess of dietary molybdenum resulted in growth retardation and loss of weight. Tolerance to molybdenum was affected by the nature of the molybdenum salt administered. 2. Molybdenum ingestion altered certain aspects of ascorbic acid metabolism in rats. The conversion of d-glucuronolactone into l-ascorbic acid in vitro and the oxidative breakdown of l-ascorbic acid by liver enzymes decreased with high molybdenum intakes. The activity of liver uronolactonase was slightly inhibited. The activities of l-gulonate dehydrogenase and l-gulonate decarboxylase were not affected appreciably. 3. Molybdenum supplementation of the control diet resulted in an increase in ascorbic acid content of spleen and adrenal gland, and in a marked decrease in the urinary excretion of ascorbic acid and glucuronic acid. The implications of these findings are discussed.

The Effect of Dietary Molybdenum Upon Growth, Hemoglobin, Reproduction and Lactation of Rats

Molybdenum as sodium molybdate was fed to weanling rats and to mature rats in order to study the effect of molybdenum upon growth and reproduction. The gain in weight of both sexes was retarded, but males were affected to a greater extent than females. Seventy-five percent of the males which were fed from weaning on a diet containing 80 and 140 p.p.m. of molybdenum were sterile. Limited histological examination showed some testicular degeneration. Fertility and gestation in females were not affected by the quantities of molybdenum fed, but there was some interference with normal lactation.

Effect of Dietary Molybdenum Upon Chicks and Poults.

SummaryGrowth of chicks and poults was depressed by approximately 25% by the addition of 300 p.p.m. molybdenum to their rations. The addition of copper to the rations containing molybdenum caused slightly improved growth. There was no evidence of anemia or diarrhea in birds on the high molybdenum diets. Poults fed high molybdenum rations for over 4 weeks had normal feather pigmentation.