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Urea poisoning
Urea is used in ruminant feed as a cheap source of nitrogen: the microbes in the rumen transform it into ammonia, then into proteins usable by the animal. This route is effective as long as it remains slow and steady. If the cow swallows to...
What is it?
Urea is used in ruminant feed as a cheap source of nitrogen: the microbes in the rumen transform it into ammonia, then into proteins usable by the animal. This route is effective as long as it remains slow and steady.
If the cow swallows too much at once, the transformation goes into overdrive. The ammonia produced exceeds what the flora can use, passes into the blood, and the liver is no longer able to neutralize it. Ammonia is a nervous system poison.
Signs appear very quickly, often within an hour of ingestion, and death can occur within a few hours. It is one of the most rapid poisonings encountered in cattle breeding.
Key point
Absolute life-threatening emergency. Signs often appear within an hour of ingestion and death can occur within a few hours: call the veterinarian as soon as you suspect it, without waiting for it to worsen.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Rapid onset, often less than an hour after ingestion.
Agitation, worry, the animal turns in circles and moves aimlessly.
Profuse and foamy salivation, grinding of teeth, trembling of the muzzle muscles.
Generalized muscle tremors that intensify, staggering gait, incoordination.
Bloating of the belly, often marked.
Rapid, difficult breathing, groaning, abdominal pain.
Kicks towards the stomach, back arched.
Then fall, convulsions, animal lying on its side pedaling, unable to get up.
Death generally occurs within a few hours after the onset of symptoms, sometimes sooner.
In a batch, several animals are affected at the same time: this is a major orientation element.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Accidental access to nitrogen fertilizer containing urea, stored in an open room or placed near animals: this is the most common cause.
Mixing error in the ration, urea poorly distributed or concentrated in part of the food.
Urea blocks or nitrogen supplements left in free access to hungry or thirsty animals, who lick them without measure.
Sudden introduction of urea into the ration, without a period of adaptation of the rumen flora.
Ration low in energy and quickly available sugars: the microbes cannot then transform the ammonia into proteins, and it accumulates.
Animals fasting or deprived of water, which consume too quickly.
Drinking water contaminated by dissolved fertilizer, a classic situation after cleaning a spreader near a water trough.
Storage of nitrogen fertilizer accessible to animals or close to herd circulation areas.
Animals not accustomed to urea, or restart after interruption of distribution.
Animals that are hungry, thirsty, or rush to the trough after a lack of food.
Poorly adjusted mixer or rough manual mixing.
Ration low in energy, poor quality fodder.
Animals with poorly functioning livers, more sensitive to ammonia.
Extreme heat, which increases water consumption and modifies eating behavior.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The diagnosis is above all a question of context: several animals affected at the same time, nervous signs appearing very quickly, and possible access to urea or fertilizer.
Report immediately to the veterinarian everything the animals may have eaten or drunk, and for how long: this is the most useful information.
He examines the nervous state, breathing, filling of the belly and heart rate.
An analysis of the contents of the rumen or blood can confirm excess ammonia, but the results often come after the decision has been made: treatment should not wait.
In the event of mortality, a post-mortem examination and sampling of rumen contents helps confirm the cause and protect the rest of the flock.
Other causes of sudden nervous signs in a batch are ruled out in parallel: other poisonings, tetany, nervous diseases.
Treatment
It is an absolute emergency: the prognosis depends on the speed of intervention. Call the veterinarian immediately.
Immediately remove access to the suspected source and remove all animals from the lot, including those that do not yet show signs.
The veterinarian seeks to acidify the contents of the rumen to block the passage of ammonia into the blood, and to dilute this content; it simultaneously treats bloating, convulsions and shock.
A probe can be passed to evacuate gases and administer products directly into the rumen.
Do not pour anything into the mouth of a convulsing, staggering or lying animal: it no longer swallows and the liquid goes into the lungs.
Place affected animals in a quiet area, on thick bedding, away from obstacles on which they could injure themselves during convulsions.
Even animals that appear unharmed should be monitored closely for several hours: signs may appear with a delay.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention is almost entirely a question of tidiness and discipline.
Store nitrogen fertilizers in a locked room, out of reach of animals and away from traffic corridors, water troughs and feeding areas. A bag ripped open in an accessible shed is enough to decimate a lot.
Never rinse a fertilizer spreader near a water trough, a pond or a water point used by the herd.
If you use urea in food, do so only on veterinary advice or from a nutrition specialist, with a perfectly homogeneous mixture.
Always introduce it gradually, over several days, to let the rumen flora adapt, and do not suddenly interrupt it and then resume it at the same level.
Ensure a ration sufficiently provided with energy: without energy, microbes do not transform ammonia and an accident becomes possible even with a moderate intake.
Never feed urea to hungry or water-deprived animals, and keep clean water available at all times.
Avoid freely accessible nitrogen blocks without supervision, particularly for animals that are not used to them.
Train all the people who prepare the ration: most accidents come from a handling error.
Possible complications
Rapid death, often within a few hours, in the most exposed animals.
Asphyxia due to associated bloating, which worsens the picture.
False swallowing and pneumonia if a liquid has been administered to a convulsing animal.
Injuries and fractures during seizures.
Abortion in surviving pregnant females.
Long-lasting damage to the liver or kidneys in some survivors.
Animals that recover generally do so without any nervous after-effects, but may remain behind in production for several weeks.
When to see a veterinarian
Several animals exhibit tremors, profuse salivation and a staggering gait at the same time: call immediately, this is a life-threatening emergency.
You notice a torn bag of fertilizer or an open room into which animals may have entered: notify the veterinarian even if no animal appears sick.
An animal convulses, lies on its side and pedals.
The stomach swells quickly and breathing becomes difficult.
An animal died suddenly shortly after a ration distribution: have the entire batch examined without delay.
Prognosis
The prognosis depends on the quantity ingested and especially the time before treatment: a few tens of minutes make the difference.
Animals treated at the first signs can recover completely in one to two days.
Those who are already lying down and convulsing when the veterinarian arrives have a very guarded prognosis.
Survivors generally return to normal life, with a temporary drop in production.
In an exposed flock, mortality can be significant and affect several animals in a very short time.
Frequently asked questions
My cows have had access to a bag of fertilizer, what should I do right away?
Remove all animals from the area immediately, cut off access and call the veterinarian without waiting for signs to appear. Specify the type of fertilizer, the amount that may have been consumed and the time. Do not administer anything yourself.
Is urea dangerous in itself in the ration?
No, used correctly it is a common tool in ruminant feeding. The danger comes from the quantity swallowed at once, from a poorly done mixture, from too rapid an introduction or from a low-energy ration. It is the use, not the product, which creates the accident.
Why are several animals affected at the same time?
Because the source is common: a trough, a block, a ripped bag or a contaminated water trough. This collective nature and the very rapid appearance of signs are two elements which strongly point towards poisoning.
Will an animal that has survived have any after-effects?
Generally not on a nervous level. However, it may produce less for a few weeks, and a pregnant female may abort. The veterinarian will tell you what monitoring to put in place.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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