Young quail were fed feed spiked with either soluble sodium molybdate or insoluble molybdenum disulfide, the main mineral form in molybdenite ore, for 30 days. Soluble molybdate raised molybdenum in serum, kidney, liver and bone and reduced growth at high doses, with recovery after clean feed. Molybdenum disulfide caused no adverse effects even at the highest dose, which the authors attribute to its low bioavailability.
Key numbers
- Soluble sodium molybdate: no-observed-adverse-effect concentration 1200 mg molybdenum/kg feed (134 mg/kg body weight/day); lowest-observed-adverse-effect concentration 2000 mg/kg feed (253 mg/kg body weight/day), based on body weight and food consumption (Discussion, p. 300; Abstract, p. 291).
- Molybdenum disulfide: no adverse effects at the highest dose, 5000 mg molybdenum/kg feed (about 545 mg/kg body weight/day) (Abstract, p. 291; Table 1, p. 295).
- Measured feed concentrations were 100 to 112% of target; control feed 2.2 mg/kg molybdenum and 26.4 to 31.2 mg/kg copper across diets, dry weight (Table 1, p. 295).
- Long-bone molybdenum at day 30: control 551.9 ng/g dry weight; 3000 mg/kg sodium molybdate group 57,750 ng/g; 5000 mg/kg molybdenum disulfide group 1278 ng/g (Table 3, p. 298).
- Serum molybdenum at day 30: control 54.5 ng/mL (reported as ppb); sodium molybdate groups 756.7 to 1911; molybdenum disulfide groups 71.9 to 97.4; values fell by day 35 after clean feed (Table 3, p. 298).
- No treatment-related mortality or lesions occurred with either form (Abstract, p. 291).
Methods (brief)
Nine groups of 12 birds received control feed, sodium molybdate dihydrate at 420, 700, 1200, 2000 or 3000 mg molybdenum/kg feed, or molybdenum disulfide at 700, 2000 or 5000 mg/kg. Six birds per group were killed at day 30 and six after a 5-day recovery. Feed and tissues were digested in nitric acid and analyzed for molybdenum and copper by ICP-MS. Groups were compared by ANOVA with Dunnett’s test.
Evidence fitness
Supports statements that the chemical form of molybdenum strongly affects its uptake and toxicity, and that soluble molybdate accumulates in bone and other tissues. It is an avian ecological-risk study at doses far above normal diets and does not support human toxicity values or food-safety limits.
Limitations
Short exposure in juvenile birds of one species; reproductive effects were not studied. The methods text lists the middle molybdenum disulfide dose as 3000 mg/kg in one place and 2000 mg/kg elsewhere; Table 1 reports 2000. Financial support came from Chevron Energy Technology Company, and two authors were Chevron employees; the authors declare no conflicts of interest.
Related evidence
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