The Resistance of a Cow

Summary of The Resistance of a Cow

by WNYC Studios

51m•April 17, 2026
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Overview of The Resistance of a Cow (Radiolab — WNYC Studios)

This Radiolab episode investigates a strange, persistent complaint from dairy farmers: cows refusing to drink clean water—and instead drinking each other’s urine. Reporters trace these incidents to a contested explanation called “stray voltage” (electricity leaking into farm infrastructure), review the history and science of electrical exposure on farms, and weigh conflicting evidence from farmers, vets, electricians, and academic researchers.

Story arc / what happens in the episode

  • A Danish reporter (Klara Grunel) visits Gregus Christensen’s farm where ~200 cows won’t drink trough water; they sniff it, then react by urinating and drinking others’ urine. Local “cow whisperer” Gitte reacts as if the farm is possessed and blames a nearby high‑voltage facility (Viking Link).
  • The pattern reappears in other Danish farms and in multiple U.S. cases (notably Minnesota). Farmers describe cows that stop drinking, stop eating, get infections, lose milk production, and sometimes die.
  • Many farmers believe stray voltage—electricity finding its way into troughs, concrete, metal—causes the behavior. Some have successfully sued utilities; others were told their problems were managerial (feed, herd management, milking parlors).
  • Investigations and experiments over decades produce conflicting conclusions: some lab/field work suggests thresholds protecting cows are adequate; a more recent on‑farm study suggests cows’ electrical resistance is lower than the conventional number, implying greater sensitivity.
  • The episode ends without definitive consensus, but with cases (e.g., Minnesota farmer Jill) where electricians found and fixed stray voltage and cows recovered, and with the observation that the issue may grow as electrical infrastructure and demand expand.

Key concepts and findings

  • Stray voltage: unintended electrical potential that can appear on grounded surfaces (metal, water troughs, concrete) on farms. Even small currents may change animal behavior.
  • Basic electricity refresher (hose analogy):
    • Voltage = pressure at the spigot.
    • Current = flow of water through the hose.
    • Resistance = hose diameter; lower resistance → more current for same voltage.
  • Cow resistance debate:
    • Historic consensus number: ~500 ohms (“500‑ohm cow”) used to set thresholds for acceptable stray voltage.
    • Newer on‑farm study (Idaho) measured many cows and reported a mean closer to ~200 ohms — implying cows in wet/free‑stall environments are more conductive and more sensitive than previously thought.
    • The Idaho data/report hasn’t been fully published/replicated and some materials are reportedly misplaced; peer‑reviewed literature still largely supports the 500‑ohm standard.
  • Behavior and physiology explanations:
    • Stray voltage can produce tingling sensations comparable to a 9‑volt battery on the tongue; cows may avoid troughs if they sense electric shocks.
    • Veterinarians note other causes for urine drinking and water aversion: electrolyte/mineral deficiencies (e.g., potassium), udder infections, overcrowding, changes from tie‑stall to free‑stall systems, herd management and feed formulation—especially as dairies scaled up.
    • Wet, manure‑soaked environments reduce resistance and increase conductivity, making modern free‑stall parlors different from older tie‑stall barns where the original resistance measurements were taken.

Evidence, disputes, and outcomes

  • Large state programs: Wisconsin conducted thousands of stray‑voltage investigations (since ~1990); <3% of farms exceeded the behavior threshold based on the 500‑ohm standard.
  • Electricians and some farmers report thousands of resolved stray‑voltage cases (one electrician estimated 4,000–5,000 cases in his career).
  • Legal actions: some farmers won lawsuits against utilities claiming milk loss and herd damage due to stray voltage.
  • Counterarguments from some researchers and utilities: most farms don’t exceed regulatory thresholds, and many cow health problems are attributable to management, infections, or nutrition rather than stray electricity.
  • Practical fixes: when stray voltage is found, it is generally straightforward to identify and remediate (rewiring, grounding fixes, isolation) and many farmers report recovery of herd health after repairs.

Broader context and implications

  • Agricultural modernization: the shift from individual tie stalls (easier to monitor single animals) to large free‑stall barns and centralized parlors changed herd dynamics, shared water troughs, and environmental conductivity.
  • Infrastructure growth: rising electricity demand (new data centers, electrification efforts) means more high‑voltage transmission lines and substations—more siting near rural lands—stirring concerns about further stray‑voltage incidents.
  • Social/political: power‑line construction has provoked farmers’ protests historically; stray voltage became both a technical problem and a political/legal battleground—sometimes a way for farmers to point to an external cause rather than internal management.

Notable voices and people mentioned

  • Reporters/producers: Matt Kilty, Simon Adler, Klara Grunel (Zetland).
  • Farmers: Gregus (Denmark), Jill Nelson (Minnesota).
  • Electricians/consultants: Larry Neubauer (dairy electrician).
  • Academics/researchers: Doug Reinemann (UW–Madison, biological systems engineering), Nigel Cook (UW Veterinary), Richard Norell (Idaho dairy scientist), David Nye (historian of technology).
  • Other: Gitte (Danish consultant who used a pendulum and believed the nearby Viking Link station caused electrical harm).

Main takeaways

  • There is a real, recurring farmer complaint—cows avoiding water and drinking urine—that’s sometimes linked to stray voltage but also has many alternative causes (nutrition, infections, management, social stress).
  • The science is complex and contested: traditional standards (500 ohms) come from older testing contexts; preliminary on‑farm measurements suggest lower resistance in modern barns (≈200 ohms), which would make cows more sensitive to small voltages—this finding is not yet universally accepted or fully published.
  • Where stray voltage is actually detected, repairs often yield quick improvements in herd health—so testing and fixing electrical issues is a practical first step for worried farmers.
  • The issue sits at the intersection of animal physiology, changing agricultural practices, electrical engineering, and regulatory/legal responses; it is likely to remain relevant as electricity infrastructure expands.

Practical recommendations (for farmers, veterinarians, and policymakers)

  • If cows avoid troughs or drink urine, investigate systematically: vet check for infections/electrolyte issues, review feed/mineral programs, evaluate stocking density and water access.
  • Test for stray voltage: hire experienced dairy/electrical specialists to measure voltage and current on troughs, metal fixtures, and animal contact surfaces. Grounding and wiring faults can be fixed.
  • For policymakers/utilities: consider updated, peer‑reviewed, on‑farm resistance data reflecting modern barn conditions when setting safety thresholds; provide clear standards and rapid investigation pathways for farmers.
  • For researchers: replicate and publish on‑farm resistance studies in free‑stall barns to resolve the 500 vs 200‑ohm debate with transparent methods and datasets.

Memorable lines / moments

  • The surreal description of cows urinating and other cows immediately turning to drink the spray—used as visceral evidence there’s something abnormal happening on those farms.
  • The 9‑volt battery analogy used to convey what a cow might feel from stray voltage.
  • The image of a farmer selling his herd and becoming a potato farmer after prolonged, unresolved herd problems—underscores the human cost.

Uncertainties that remain

  • No disciplinary consensus: peer‑reviewed literature still largely supports the 500‑ohm standard, but newer on‑farm data suggest that modern cows in wet/free‑stall barns might have lower resistance; data publication and replication are needed.
  • Multi‑factor causality: many episodes likely arise from a mix of stray voltage, nutrition, infection, barn design, and herd management—not a single smoking‑gun cause in every case.

Sources and contributors are the Radiolab episode team (reporting and interviews with the people listed above).