NAVLE Urinary

Bovine Ethylene Glycol Toxicity Study Guide

📅 March 28, 2026 ⏱ 25 min read

Ethylene glycol (EG) toxicosis is a rare but life-threatening condition in cattle caused by ingestion of antifreeze or contaminated feedstuffs.

Overview and Clinical Importance

Ethylene glycol (EG) toxicosis is a rare but life-threatening condition in cattle caused by ingestion of antifreeze or contaminated feedstuffs. Although more commonly encountered in small animals, bovine cases occur through accidental exposure to automotive antifreeze, contaminated water sources, or adulterated feed products. The condition results in acute renal failure due to the formation of calcium oxalate crystals in renal tubules following hepatic metabolism of ethylene glycol to toxic metabolites.

Understanding the pathophysiology, clinical presentation, and treatment options is essential for veterinarians practicing in both dairy and beef cattle operations. Prompt recognition and early intervention are critical for survival, though prognosis remains guarded to poor once clinical signs develop.

Step/Enzyme	Metabolite	Clinical Significance
Alcohol Dehydrogenase (ADH)	Glycoaldehyde	CNS depressant; rate-limiting step; target of antidotal therapy (fomepizole/ethanol)
Aldehyde Dehydrogenase	Glycolic Acid	PRIMARY cause of metabolic acidosis; correlates with clinical severity
Glycolate Oxidase	Glyoxylic Acid	Intermediate metabolite; can be detoxified via thiamine and pyridoxine-dependent pathways
Glycolate Oxidase	Oxalic Acid	Binds calcium forming calcium oxalate crystals; causes acute tubular necrosis and renal failure

Sources of Exposure

Ethylene glycol is a colorless, odorless, sweet-tasting liquid commonly found in automotive antifreeze (concentrations up to 95%), windshield deicer fluids, brake fluids, industrial solvents, and certain pharmaceutical preparations. In cattle, exposure typically occurs through:

Contaminated feed products: Industrial by-products used as cattle feed may become contaminated during processing or storage
Leaking cooling systems: Geothermal heating systems or milk taxi equipment using ethylene glycol as antifreeze
Accessible antifreeze containers: Open or discarded containers in pastures or near equipment
Abandoned vehicles: Leaking radiators from farm equipment or vehicles
Contaminated water sources: Runoff or spillage into water troughs or ponds

High-YieldThe sweet taste of ethylene glycol makes it palatable to cattle. Unlike propylene glycol (used safely as an energy supplement in ketotic cows), ethylene glycol is highly toxic and should NEVER be confused with or substituted for propylene glycol in cattle treatment.

Animal Category	Minimum Lethal Dose	Notes
Preruminant Calves	2 mL/kg body weight	MORE susceptible than adult cattle
Ruminating Cattle	5-10 mL/kg body weight	Rumen metabolism may provide some protection
Comparative: Dogs	4.4-6.6 mL/kg	For reference
Comparative: Cats	1.4 mL/kg	Most sensitive species

Toxicokinetics and Metabolism

Absorption and Distribution

Ethylene glycol is rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 1 to 4 hours post-ingestion. The compound distributes throughout total body water due to its high water solubility. Approximately 80% undergoes hepatic metabolism, while 20% is excreted unchanged through the kidneys.

Metabolic Pathway

Toxic Dose in Cattle

NAVLE TipRemember that PRERUMINANT CALVES are MORE susceptible than ruminating adult cattle (2 mL/kg vs 5-10 mL/kg). This is important for NAVLE questions involving young calves exposed to antifreeze.

Stage	Time Post-Ingestion	Clinical Signs
Stage 1: CNS Depression	0.5-12 hours	Neurologic: Ataxia (staggering gait), depression, weakness GI: Hypersalivation, anorexia, diarrhea Cardiovascular: Initial bradycardia, later tachycardia
Stage 2: Cardiopulmonary	12-24 hours	Respiratory: Tachypnea, dyspnea (compensatory hyperventilation) Cardiovascular: Tachycardia, dehydration (sunken eyes) Metabolic: Severe metabolic acidosis
Stage 3: Renal Failure	24-72+ hours	Renal: Oliguria progressing to anuria, uremia Neurologic: Recumbency, convulsions, coma Hematologic: Hemoglobinuria, epistaxis (at high doses) Outcome: Death typically occurs 1-6 days post-ingestion

Clinical Signs and Stages of Toxicosis

Clinical signs of ethylene glycol toxicosis in cattle develop in a predictable triphasic pattern, though overlap between stages is common. The severity and onset depend on the dose ingested.

Clinical Signs Specific to Cattle

Ataxia and staggering gait - often the first clinical sign observed
Hypersalivation - profuse drooling
Diarrhea - commonly reported in bovine cases
Sunken eyes - indicates severe dehydration
Paraparesis progressing to recumbency - inability to rise
Tachypnea and increased respiratory effort - due to metabolic acidosis
Hemoglobinuria and epistaxis - seen at higher doses (10 mL/kg)

Parameter	Findings
Blood Urea Nitrogen (BUN)	Markedly elevated (azotemia) - indicates renal failure
Serum Creatinine	Elevated - confirms azotemia
Blood pH	Decreased (metabolic acidosis) - due to glycolic acid accumulation
Serum Calcium	HYPOCALCEMIA - calcium binds to oxalate forming crystals
Plasma Osmolality	Increased osmolal gap (early) - due to unmetabolized ethylene glycol
Anion Gap	Elevated - high anion gap metabolic acidosis
Neutrophil Count	Neutrophilia - consistent finding
Hemolytic Anemia	May occur at higher doses

Diagnosis

History and Clinical Suspicion

A diagnosis of ethylene glycol toxicosis should be suspected in cattle presenting with acute neurologic signs (ataxia, depression) followed by acute renal failure, particularly when there is a history of potential exposure to antifreeze or contaminated feed.

Clinicopathologic Findings

Urinalysis Findings

The hallmark finding on urinalysis is the presence of calcium oxalate crystals. Two morphologic forms are recognized:

Calcium Oxalate Monohydrate (COM): Appear as flat, elongated, six-sided "picket fence" or dumbbell-shaped crystals. The picket fence form is HIGHLY SPECIFIC for ethylene glycol toxicosis and is not seen in normal animals.
Calcium Oxalate Dihydrate (COD): Appear as octahedral or "envelope-shaped" crystals. Less specific as they can occur in normal urine.

Exam Focus: The triad of HIGH ANION GAP METABOLIC ACIDOSIS + AZOTEMIA + CALCIUM OXALATE CRYSTALLURIA is pathognomonic for ethylene glycol toxicosis. Remember: "Picket fence" shaped calcium oxalate monohydrate crystals are SPECIFIC for ethylene glycol poisoning.

Intervention	Dose/Administration	Rationale
Fomepizole (4-MP)	Dogs: 20 mg/kg IV initially, then 15 mg/kg at 12 and 24h, 5 mg/kg at 36h (No established bovine dose)	PREFERRED ANTIDOTE - competitively inhibits alcohol dehydrogenase with 8000x greater affinity than ethanol
Ethanol	5.5 mL of 20% ethanol/kg IV every 4h for 5 treatments, then every 6h for 4 treatments (dog dose)	ALTERNATIVE if fomepizole unavailable - competitively inhibits ADH; 100x greater affinity than EG
IV Fluid Therapy	Aggressive crystalloid fluid administration (0.9% NaCl or LRS)	Maintain hydration, promote diuresis, support renal perfusion
Sodium Bicarbonate	1-2 mEq/kg IV slowly; titrate to effect	Correct metabolic acidosis; caution: may worsen hypocalcemia
Calcium Gluconate	23% calcium gluconate: 0.5-1.0 mL/kg IV slowly with ECG monitoring	Treat hypocalcemia; caution: may increase crystal formation
Thiamine (B1)	Co-factor for alternative detoxification pathway	Promotes metabolism of glyoxylic acid to non-toxic metabolites
Pyridoxine (B6)	Co-factor for alternative detoxification pathway	Promotes metabolism of glyoxylic acid to glycine (non-toxic)

Necropsy and Histopathology

Gross Pathology

Kidneys: Swollen, pale to tan or black; may have a gritty texture on cut surface
Perirenal edema: Common finding in cattle and pigs
GI contents: Black, foul-smelling gastrointestinal contents reported
Other findings: May include epicardial ecchymoses, frothy bloat (if death is rapid)

Histopathologic Findings

The definitive diagnosis is made by histopathologic examination of kidney tissue demonstrating calcium oxalate crystals within renal tubules.

Acute tubular necrosis: Necrotic tubular epithelium with sloughing
Intratubular crystals: Translucent, fan-shaped, rhomboid, or rosette crystals in tubular lumens
Birefringence under polarized light: Crystals are CLEAR on H&E stain but show BRIGHT MULTICOLORED BIREFRINGENCE under polarized light microscopy
Pink intratubular casts: Proteinaceous material within damaged tubules
Interstitial nephritis: Lymphocytic infiltration in interstitium

High-YieldOn NAVLE, remember that calcium oxalate crystals are TRANSLUCENT (clear) on standard H&E staining but show BRIGHT BIREFRINGENCE under POLARIZED LIGHT. This is critical for histopathologic diagnosis.

Confirmatory Testing

Serum/plasma ethylene glycol measurement: Gas chromatography with flame ionization detection; levels detectable for 48-72 hours post-ingestion
Glycolic acid levels: Correlate more closely with clinical severity than parent compound
Feed/water analysis: Test suspected contaminated feedstuffs or water sources

Presentation	Prognosis
Early presentation (less than 6h)	Fair with aggressive treatment; renal function may be preserved
Late presentation (greater than 12-24h)	POOR - irreversible renal damage likely; death common
Oliguric/anuric renal failure	GRAVE - indicates severe irreversible renal damage
Preruminant calves	POOR - more susceptible; lower lethal dose

Treatment

Treatment of ethylene glycol toxicosis must be initiated EARLY to be effective. Once significant renal damage has occurred, the prognosis is grave. Treatment goals include: preventing further metabolism, correcting metabolic derangements, and supporting renal function.

Treatment Protocol

NAVLE TipFOMEPIZOLE (4-methylpyrazole) is the PREFERRED antidote over ethanol because it: (1) has 8000x greater affinity for ADH, (2) does not cause CNS depression, (3) does not worsen metabolic acidosis, and (4) requires less intensive monitoring. Treatment must begin WITHIN 6-8 HOURS of ingestion to be effective.

Prognosis

Differential Diagnoses

Oxalate-containing plant toxicosis: Halogeton, pigweed (Amaranthus retroflexus), greasewood (Sarcobatus vermiculatus), sorrel, rhubarb
Other nephrotoxins: Oak toxicosis (gallotannins), aminoglycoside nephrotoxicity, heavy metal toxicosis
Causes of acute renal failure: Hemolytic-uremic syndrome, post-renal obstruction, acute pyelonephritis
Causes of metabolic acidosis: Grain overload (ruminal acidosis), diarrhea, sepsis
Neurologic diseases: Lead toxicosis, polioencephalomalacia, nervous ketosis, rabies

Prevention

Store antifreeze and other ethylene glycol-containing products in secure, labeled containers inaccessible to livestock
Promptly clean up any spills and properly dispose of used antifreeze
Remove abandoned vehicles and equipment containing antifreeze from pastures
Consider using propylene glycol-based antifreeze (less toxic) in farm equipment
Verify safety and source of all feed by-products before offering to cattle
Regularly inspect cooling systems on milk taxis and other equipment for leaks

"EG-ACID" Mnemonic for Ethylene Glycol Toxicosis:

E - Ethanol or Fomepizole for treatment (ADH inhibitors)
G - Glycolic acid causes metabolic acidosis
A - Azotemia (elevated BUN/creatinine)
C - Calcium oxalate Crystals in urine and kidney
I - Increased anion gap and osmolal gap
D - Dehydration and Depression (CNS)

Crystal Shape Memory Aid:

"MONOHYDRATE = MORE specific" - Monohydrate crystals (picket fence/dumbbell) are MORE specific for EG toxicosis. "DIHYDRATE = Diverse" - Dihydrate crystals (envelope) can occur in Diverse conditions including normal urine.

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