Molybdenum toxicosis

Question 1

Sources?

Answer 1

• Excess molybdenum
  
  • Soil rich in molybdenum, or contaminated w/ molybdenum (FL, CA, OR, NV)
  • Plants can accumulate molybdenum from soil
  • Industrial contamination (brick plants, steel mills)
  • Molybdenum-containing fertilizers
• Cu deficiency

Question 2

What states have soil rich in molybdenum?

Answer 2

Florida, California, Oregon, Nevada

Question 3

T/F: Molybdenum is an essential trace element

Answer 3

TRUE

Question 4

What is molybdenum a component of?

Answer 4

xanthine oxidase, which converts the purine xanthine to uric acid

Question 5

What does elevated molybdenum interfere with?

Answer 5

Copper absorption

Question 6

What does excess molybdenum cause?

Answer 6

Copper deficiency

Question 7

Which species is most susceptible to molybdenum toxicosis? Which is resistant?

Answer 7

Cattle are the most susceptible (though has been seen in sheep as well)

Horses and pigs are resistant

Question 8

What increases molybdenum toxicity? What decreases it?

Answer 8

High levels of dietary sulfate increases toxicity

Dietary copper decreases toxicity

Question 9

What is the max tolerable dietary level of molybdenum?

Answer 9

5-10 ppm

Question 10

Where is molybdenum absorbed from? Where is it excreted in toxic levels?

Answer 10

Absorbed from GI tract, excreted in milk in toxic levels

Question 11

Mechanism of action of molybdenum toxicosis (plus copper roles)?

Answer 11

• Copper deficiency
• Copper is involved in hematopoeisis, CT metabolism, myelin formation in newborns, pigmentation, and bone formation
• Copper is a component of essential enzymes such as cytochrome oxidase and aromatic amino acid-metabolizing enzymes (tyrosinase, dopamine hydroxylase, MAO)
• Copper-containing proteins (cupreins) in most aerobic cells have superoxide dismutase activity

Question 12

Clinical signs?

Answer 12

• Severe diarrhea (greenish, with fluids and gas bubbles) after 8-10 days following exposure
• Rough hair coat and depigmentation (achromotrichia) of hair especially around the eyes (‘spectacled’ appearance)
• Loss of weight, anemia, osteoporosis and exostosis, lameness, and pica
• Decreased libido in bulls and infertility in cows

Question 13

What is elevated on the lab diagnosis?

Answer 13

Elevated molybdenum in the blood (> 0.1ppm) and in the liver (> 5ppm)

Question 14

What is decreased on the lab diagnosis?

Answer 14

• Decreased Cu in the blood (< 0.6ppm) and liver (< 10ppm)
• Decreased cytochrome oxidase activity (Cu deficiency)

Question 15

DDx?

Answer 15

• Selenium deficiency (?)
• Frostbite
• Fluoride poisoning
• Ergot

Question 16

Treatment?

Answer 16

• Copper glycinate SC/IM (60mg for calves, 120mg for cattle)
• Cu sulfate added to the diet (1g daily per adult cow)