The regular occurence of molybdenum in very low concentration in a wide range of animal tissues has raised its interest in the past four decades. This interest in the biological significance of molybdenum received greater attention from the discovery of its role as a cofactor in many enzymes (oxydase, reductase) and from the demonstration that their activity is highly dependant upon its presence.
Since then, it has been well established that this trace element is essential for mammals, in particular ruminants, because it favours the rumenal fixation of sulfur,
its reduction in sulfide followed by its subsequent oxydation into sulfate. Also well known is the antagonism between copper and molybdenum. It finds its origin in the inhibition, by the thiomolybdanes, of the copper dependent enzymes which catalyse the intestinal and hepatic absorption of copper.
The presence of dietary inorganic sulfate together with molybdenum may also exert an adverse effect on copper retention.Consequently, to prevent any direct or indirect molybdenum toxicity, attention has to be paid to the recommended Mo supplementation dependingon the animal species. Only very small concentrations are required.
Main sources Sodium molybdate dihydrate Quality and selection parameters
The water soluble properties of the sodium and ammonium salts ensure an excellent bio-availability of the supplied molybdenum source. The total guaranteed molybdenum content and perfect solubility are selection criteria.
Analytical methods
Total molybdenum  - X-Ray fluorescence 
Cu / Pb / Fe / Ca   - Spectrometric Atomic absortion (SAA) 
SiO2   - photometric titration