Deficiency effects molybdenum

Both Mo deficiencies in crops and toxicity in foraging animals have been reported. Deficiency of molybdenum is possible at levels <0.1 ppm, while toxic effects are observed in cattle feeding on plants with Mo levels > 10 ppm by dry weight. The average Mo contents in soils range from 0.1 to 40 ppm. 

Soil Nutrient. Molybdenum has been widely used to increase crop productivity in many soils woddwide (see Fertilizers). It is the heaviest element needed for plant productivity and stimulates both nitrogen fixation and nitrate reduction (51,52). The effects are particularly significant in leguminous crops, where symbiotic bacteria responsible for nitrogen fixation provide the principal nitrogen input to the plant. Molybdenum deficiency is usually more prominent in acidic soils, where Mo(VI) is less soluble and more easily reduced to insoluble, and hence unavailable, forms. Above pH 7, the soluble anionic, and hence available, molybdate ion is the principal species. 

Chromium has proved effective in counteracting the deleterious effects of cadmium in rats and of vanadium in chickens. High mortality rates and testicular atrophy occurred in rats subjected to an intraperitoneal injection of cadmium salts however, pretreatment with chromium ameliorated these effects (Stacey et al. 1983). The Cr-Cd relationship is not simple. In some cases, cadmium is known to suppress adverse effects induced in Chinese hamster (Cricetus spp.) ovary cells by Cr (Shimada et al. 1998). In southwestern Sweden, there was an 80% decline in chromium burdens in liver of the moose (Alces alces) between 1982 and 1992 from 0.21 to 0.07 mg Cr/kg FW (Frank et al. 1994). During this same period in this locale, moose experienced an unknown disease caused by a secondary copper deficiency due to elevated molybdenum levels as well as chromium deficiency and trace element imbalance (Frank et al. 1994). In chickens (Gallus sp.), 10 mg/kg of dietary chromium counteracted adverse effects on albumin metabolism and egg shell quality induced by 10 mg/kg of vanadium salts (Jensen and Maurice 1980). Additional research on the beneficial aspects of chromium in living resources appears warranted, especially where the organism is subjected to complex mixtures containing chromium and other potentially toxic heavy metals. 

O Gorman, J., F.H. Smith, D.B.R. Poole, M.P. Boland, and J.F. Roche. 1987. The effect of molybdenum-induced copper deficiency on reproduction in beef heifers. Theriogenology 27 265. 

Subclinical effects are often observed when molybdenum levels in soil exceed 3 pg/g an excess of molybdenum in forage is toxic to livestock. Deficiency diseases have been observed in livestock when soil molybdenum levels are below 0.5 pg/g. 

The determination of molybdenum in soil is of interest because molybdenum is necessary for normal crop growth, but an excess in forage has a toxic effect on ruminants. The absorption of molybdenum by plants is influenced by other soil components, especially extractable iron, pH and organic matter. The average abundance of molybdenum in soils is about 2 ppm, but deficient soils can have much less than 1 ppm [171]. Jiao et al. [172] and Rowbottom [173] have reviewed methods for the determination of molybdenum in soils. 

Vanadium nitrogenase is produced by certain bacteria grown in molybdenum-deficient environments. It is effective in the reduction of N2 and other nitrogenase substrates, although with less activity than the Mo—Nase. The enzyme resembles the Mo analogue (see Sections 17-E-10 and 18-C-13) in the construction and structure of the prosthetic groups, as well as in its functions.101 It consists of a FeV protein, FeVco, and an iron protein (a 4Fe—4S ferredoxin). 

Molybdate is known to induce copper deficiency, ft was found that the administration of molybdenum compounds, particularly with added sulfate, impaired copper metabolism in ruminants. Tetrathiomolybdate has been used to treat patients who were intolerant to D-penicillanune, trientine, and zinc. Tetrathiomolybdate seems to act both by blocking the intestinal absorption of copper and keeping it in a metabolically inert chelated form, which is not taken up by the liver. However, it induces only a modest cupriuresis. There are also known toxic effects of tetrathiomolybdate on the skeletal system of growing animals. Thus one should be extremely careful in administering this compound. It should be considered as an experimental drug. 

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