Dietary molybdenum as a putative copper antagonist in the horse.

The research investigated whether an increase in dietary molybdenum could interfere with copper metabolism in horses. The study showed no evidence of interference in copper metabolism when the horses’ diets were supplemented with molybdenum.

Methodology

• The researchers utilized four horses, which were stabled and fed a diet consisting of hay and 2 kg of oats per day for a month.
• The basic diet was then supplemented with molybdenum, given at a rate of 20 mg/kg dry matter for 4.5 months.
• For a month within this period, the diet was also supplemented with sulfur at a rate of 1.2 g/kg dry matter.
• Jugular blood samples were obtained at intervals ranging from two to 20 days. These were analyzed to monitor any impact on plasma copper levels or changes to trichloroacetic acid (TCA) insoluble copper in the plasma.

Findings

• The analyses of the jugular blood samples showed no evidence of a decline in total plasma copper, nor an increased proportion of TCA insoluble copper in plasma over the 4.5-month period.
• Two other horses were given 99molybdenum while being fed the same diet. 99Molybdenum appeared rapidly in plasma, but the radioactivity was quickly cleared with a half-life of 7 to 10 hours.
• The 99molybdenum was identified as (99Mo)-molybdate, without any evidence of the persistent, protein-bound (99Mo)thiomolybdates which appear in ruminants.

Conclusion

• The results of the study suggest that increasing the amount of molybdenum in a horse’s diet is not likely to cause interference with the metabolism of copper.
• This is important information for horse owners and veterinarians, as it can guide dietary decisions to ensure nutrients are used effectively in the horse’s body.