Molybdenum in the nutrition of the rat.

Some years ago a group of experimentalists (l-3) observed that the scouring of cattle on the so called “teart” pastures of England could be traced to the high molybdenum content of the soil and herbage. Feeding molybdenum salts reproduced the symptoms. Subsequently it was found t:hat feeding copper sulfate as a drench prevented or cured the condition. Apparent.ly a similar high molybdenum area is present in California (4). Tn Australia, further evidence of the rBle of copper in molybdenosis was discovered (5). Molybdenum fed to sheep and cattle caused loss of liver copper even when the copper intake in the diet was increased. Recently several other interesting interactions between nutritional elements have appeared. Thus it was found (6) that copper will counteract t,he anemia caused by feeding zinc to rats. It is also claimed (7) that arsenic and manganese fed in addition to iron and copper salts will allow greater hemoglobin production in rats on a milk diet than when only iron and copper are added as the mineral supplement. It is clear from these studies that the toxicity, deficiency, metabolism, etc., of one element, at least in herbivorous animals, may be profoundly influenced by the levels of certain of the ot,her elements of the diet. Molybdenum has been fauna capable of combining with catechol in a 1: 2 molar ratio (8). It was shown that such a combination reduced t,he toxicity of catechol for bacteria, thus allowing proliferation of the microorganisms in an otherwise t,oxic concentration of catechol. It was suggested that these reactions could account for the dia.rrhea seen in cat,tle suffering from molybdenosis. This paper shows that molybdenum in the form of sodium molybdate retards the growth of rats on a purified ration. The molybdenum toxicity can be overcome by feeding larger amounts of copper as copper sulfate or by the incorporation into the diet of 5 per cent whole liver substance but not by feeding higher levels of iron, zinc, or cobalt. In another experiment the fate of a given dose of molybdenum (labeled with radioactive Mogg) when fed either alone or with copper or catechol was investigated.