Molybdenum
Although molybdenum functions as a component for the enzymes xanthine oxidase, sulfite oxidase and aldehyde oxidase, requirements for it are not established. Molybdenum may enhance microbial activity in the rumen in some instances. There is no evidence molybdenum deficiency occurs in cattle under practical conditions. Metabolism of molybdenum is affected by both copper and sulphur. Sulfide and molybdate interact in the rumen to form thiomolybdates, which results in decreased absorption and altered postabsorptive molybdenum metabolism. Sulphate shares common transport systems with molybdate in the intestine and kidney, decreasing intestinal absorption and increasing urinary excretion of molybdate. It is well documented that relatively low dietary molybdenum can cause copper deficiency and that increasing dietary copper can overcome molybdenum toxicity. Forages vary greatly in molybdenum concentration, depending on both soil type and pH. Neutral or alkaline soils, coupled with high moisture and organic matter, favor forages molybdenum uptake. Cereal grains and protein supplements are less variable than forages in molybdenum