The Resistance of a Cow

What It Covers

Danish journalist Clara Groenel investigates why cows on farms near power infrastructure refuse water and drink each other's urine. The trail leads through Wisconsin stray voltage lawsuits, a decades-long scientific debate over cow electrical resistance, and a disputed 2016 Idaho study challenging the foundational 500-ohm standard used in farm safety regulations.

Key Questions Answered

• •Stray Voltage Threshold: Wisconsin established a behavioral sensitivity threshold for cows after UW Madison researcher Doug Reineman found that a nine-volt equivalent stimulus triggers measurable physical responses. Since 1990, over 9,000 Wisconsin farm investigations found fewer than 3% of farms exceeded this threshold, suggesting most reported stray voltage cases have alternative explanations worth investigating before blaming electrical infrastructure.
• •Cow Resistance Standard: The 500-ohm resistance value used in all current farm electrical safety regulations was derived from measurements taken on cows in old tie-stall barns. A 2016 Idaho study measuring 170 cows in modern free-stall environments found resistance closer to 200 ohms — meaning cows in wet manure slurry may receive double the current that current regulatory thresholds assume is safe.
• •Dietary Deficiency Mimics Stray Voltage: Veterinarian Don Sanders, with 50 years of practice, identifies potassium and sodium deficiency as the primary documented cause of cows drinking urine. High-performance dairy cows bred for maximum milk output require precisely calibrated diets; months of nutritional imbalance can trigger immune problems and urine-drinking behavior that closely resembles stray voltage symptoms, making misdiagnosis common.
• •Farm Modernization as Confounding Factor: The shift from tie-stall barns housing individual cows to free-stall operations housing 500 to 20,000 cows changed management complexity dramatically. UW Madison's Nigel Cook notes that trough space recommendations require three to four inches of perimeter per cow; farms falling to two inches create water-access stress that produces behavioral symptoms — reluctance to drink, agitation — identical to reported stray voltage cases.
• •Published Data Gap: The Idaho resistance study challenging the 500-ohm standard remains unpublished because lead researcher Rick Norell lost a critical data binder after retiring. Without peer-reviewed publication, the finding cannot shift regulatory policy. Farmers and advocates pushing for lower resistance thresholds have no published evidence to counter Doug Reineman's position that current peer-reviewed literature still supports 500 ohms as accurate.