Effects of Molybdenum and Sulfate Sulfur on Metabolism of Copper in Dairy Cattle

Experiments on first-calf Holstein heifers investigated molybdenum toxicity by adding 5 to 50 ppm molybdenum to a low-copper diet, with or without 0.3% sulfate sulfur. Heifers on diets with 5 to 50 ppm molybdenum and no added sulfate sulfur showed no toxicity symptoms like alopecia or achromatrichia, but had reduced liver and blood serum copper. Similar results were seen with 5 to 20 ppm molybdenum and 0.3% sulfate sulfur. However, 50 ppm molybdenum with 0.3% sulfate sulfur caused alopecia and achromatrichia, but no further symptoms over 625 days. Four heifers on 100 or 200 ppm molybdenum with 0.3% sulfate sulfur became emaciated and developed severe symptoms, but copper levels in the liver and blood serum remained unchanged. Adding copper to the diet corrected alopecia and achromatrichia. The study highlights the role of molybdenum in cattle nutrition and its interaction with copper.