Molybdenum
Molybdenum is a chemical element; it has symbol Mo and atomic number 42. Molybdenum is an essential trace element that is naturally present in many foods and is also available as a dietary supplement. Molybdenum is a structural constituent of molybdopterin, a cofactor synthesized by the body and required for the function of four enzymes: sulfite oxidase, xanthine oxidase, aldehyde oxidase, and mitochondrial amidoxime reducing component (mARC).
The kidneys are the main regulators of molybdenum levels in the body and are responsible for its excretion. Molybdenum, in the form of molybdopterin, is stored in the liver, kidney, adrenal glands, and bone.
Molybdenum-related cattle sickness, often linked to a condition called molybdenosis or secondary copper deficiency, is a phenomenon and has been documented in the United States and other parts of the world. Its concentration in soil varies depending on geology, with higher levels in areas with certain rock types or industrial contamination. Plants can absorb molybdenum from the soil, and levels in forage can become elevated in regions with naturally high molybdenum or human-induced contamination.
Cattle require trace amounts of molybdenum for metabolic processes, but excessive intake can be harmful. High molybdenum in forage disrupts copper metabolism in ruminants like cattle, leading to a condition known as molybdenosis. This is often a secondary copper deficiency because molybdenum forms complexes with sulfur in the rumen, creating thiomolybdates that bind copper, making it unavailable to the animal.
television
The Have Gun, Will Travel episode "Winchester Quarantine" (Season 1, Episode 4, aired October 5, 1957) involves Paladin aiding a Cherokee rancher, Joseph Whitehorse, whose cattle are accused of spreading sickness, only for Paladin to discover molybdenum in the soil as the true cause. Paladin reveals the land is poisoned by molybdenum, which affects vegetation and sickens cattle when they graze. He notes molybdenum “looks somewhat like white iron” and has been known since ancient times (referencing Pliny and Nero).
The episode implies cattle are dying or sickening, which matches molybdenosis symptoms. Molybdenosis isn’t contagious; it’s environmental, tied to specific land. The townspeople’s fear of a contagious disease reflects misunderstanding, which is plausible for the 19th-century setting. Paladin’s use of a chemist (Rheinhart) to test soil and confirm molybdenum is realistic. By the 1950s, soil and plant testing for trace elements like molybdenum was established in agricultural science, and a knowledgeable figure like Rheinhart could identify it.
Paladin’s line about molybdenum looking “somewhat like white iron” and being known since Pliny’s time is partially accurate. Molybdenum, in pure form, is a silvery-white metal, and Pliny the Elder did mention similar minerals in Roman times, though the element wasn’t isolated until 1781 by Peter Jacob Hjelm. The reference adds dramatic flair but stretches historical precision.