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environmental disease Sheep, Goat

Nitrate and nitrite poisoning

Nitrates are nitrogen compounds that plants absorb from the soil. Normally they are harmless, but in the rumen they are transformed into nitrites, and it is the nitrites which poison. Nitrites attack the blood itself: they make hemoglobin i...

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Definition Signs Causes Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

Nitrates are nitrogen compounds that plants absorb from the soil. Normally they are harmless, but in the rumen they are transformed into nitrites, and it is the nitrites which poison.

Nitrites attack the blood itself: they make hemoglobin incapable of transporting oxygen. The animal may breathe deeply, but the oxygen no longer reaches the organs. He suffocates with air filling his lungs.

The blood changes color and becomes chocolate brown: this is the sign that puts the veterinarian on the trail.

Key point

Nitrate poisoning kills in less than an hour and affects several animals at once. Faced with a flock that is suffocating after a change of forage or plot, remove the source, do not make the animals run and call the veterinarian immediately: an antidote exists and its effectiveness depends on the delay.

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:

Difficulty breathing Rapid breathing Staggering gait Tremors Excessive salivation Reduction Lying animal that does not get up Abortion Seizures Pale mucous membranes

The signs appear a few hours after access to the fodder or plot in question.

Rapid and difficult breathing, animal opening its mouth, craning its neck, breathing noisily, as if lacking air.

Abnormally colored mucous membranes: they lose their clear pink and take on a grayish, brownish or bluish tint. This unusual color is very evocative for the veterinarian.

Marked weakness, animal that staggers, stumbles, collapses at the slightest effort.

Muscle tremors, salivation, restlessness.

Refusal to move, animal that remains lying down.

Sudden fall, convulsions, rapid death in severe forms, sometimes in less than an hour.

Several animals from the same batch are affected at the same time: this is a major orientation element, since all ate the same thing.

In pregnant females who survive: abortions in the days or weeks that follow, due to lack of oxygen to the fetus.

Less affected animals recover spontaneously once removed from the source, which may provide false reassurance.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

Consumption of plants rich in nitrates. The circumstances which cause the levels to rise are well identified: prolonged drought followed by rain, significant or recent nitrogen fertilization, spreading of slurry, frost, hail, herbicides, any stress which blocks the growth of the plant while it continues to absorb nitrogen from the soil.

Plants most often involved: sorghum and corn regrowth, stressed corn, beets and their tops, cabbages and brassicas, amaranths, lamb's-quarters and other weeds on the edges of fields and manure piles.

Fodder harvested under these conditions and distributed as is: drying does not destroy nitrates, dangerous hay remains.

Drinking water contaminated with nitrates, especially in shallow wells near fertilized areas or pits.

Hungry animals released on a risky plot: they consume a lot and quickly, which makes everything worse.

Animals not accustomed to this forage: gradual adaptation reduces the risk, a sudden change increases it.

Provision of a plot or fodder at risk after a period of drought followed by rain.

Plots heavily fertilized with nitrogen or having received slurry shortly before grazing.

Animals released hungry, after transport, sorting, or a night without eating.

Distribution of beet tops, cabbage or sorghum shoots without transition or notice.

Grazing on field edges, headlands and around manure piles, rich in concentrating weeds.

Watering from a shallow well in an intensive cultivation area.

Pregnant females, particularly exposed to the consequences.

Absence of analysis of suspect fodder before distribution.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

This is an emergency: call the veterinarian immediately and remove the lot from the plot or remove the fodder.

The veterinarian relies on the respiratory picture, the color of the mucous membranes and above all on the dietary context: what the animals have just eaten, since when, in what conditions.

The chocolate brown color of the blood taken is a very strong element in favor of the diagnosis; There are rapid tests on forage and water that the veterinarian can implement.

A sample of the suspect forage, water and possibly the contents of the rumen of a dead animal makes it possible to confirm and, above all, to decide whether the rest of the stock can be distributed.

It is essential to keep a sample of the forage in question and note the plot: this will help protect the rest of the herd.

The veterinarian rules out other causes of sudden respiratory distress in the sheep, including infectious respiratory diseases and other poisonings.

Treatment

The treatment is a veterinary emergency. There is an antidote which restores the blood's ability to transport oxygen, administered intravenously by the veterinarian; its effect can be spectacular when given on time.

This product is dangerous if misused: neither the choice, nor the quantity, nor the route is up to the breeder. No farm remedy replaces this treatment.

While waiting for the veterinarian: immediately remove the fodder or remove the animals from the plot, calmly and without making them run. An animal lacking oxygen that is run dies.

Place the animals in the shade, in a quiet area, with clean water, and avoid any handling.

Do not force drink or give anything by mouth.

All animals in the group should be closely monitored for several hours, including those that appear normal: the signs do not appear at the same time in all.

The fodder or plot in question must not be redistributed until the veterinarian has made a decision with supporting analysis.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Never release hungry animals onto a plot of land at risk: distribute hay before leaving and graze at the end of the day rather than when hungry.

Gradually introduce any new fodder, particularly sorghum shoots, beet tops and brassicas.

Respect a time limit between nitrogen fertilization or spreading of slurry and putting it out to grass, and seek advice if in doubt.

Avoid grazing a crop stressed by drought, frost or hail, especially just after rain: this is the most dangerous time.

Have suspect fodder analyzed before distributing it, which is simple and inexpensive considering the risk.

Avoid field edges, headlands and the surroundings of manure piles as a food resource.

Check the quality of water in shallow wells in growing areas.

Limit access to piles of tops and harvest waste, which often concentrate problems.

Possible complications

Rapid death from lack of oxygen, sometimes of several animals from the same batch within a few hours.

Abortions in pregnant females who survive, often days to weeks later.

Lambs born weak or stillborn.

Nervous after-effects in animals having lacked oxygen for a long time.

Recurrences as long as the fodder or plot in question remains accessible.

Loss of an entire stock of fodder when the harvested batch is contaminated.

When to see a veterinarian

Several animals breathe with difficulty, mouth open, shortly after a change of fodder or plot: absolute emergency, call immediately.

An animal's mucous membranes take on a gray, brownish or bluish tint.

Animals stagger and collapse at the slightest effort.

One or more animals die suddenly after consuming regrowth, tops or new fodder.

Abortions occur in the days following such an episode.

You have distributed fodder harvested from a stressed crop: ask for advice before continuing.

Prognosis

Treated early, animals often respond very well to the antidote and recover within a few hours.

Animals already lying down and convulsing have a poor prognosis.

Pregnant females that survive may subsequently abort, even if they appear recovered.

At the scale of the batch, the prognosis depends on the speed of removal of the source and the call to the veterinarian: it is a poisoning where a few minutes change the result.

Frequently asked questions

Is dry fodder less dangerous than green fodder?

No. Drying does not destroy nitrates: hay harvested from a loaded crop remains dangerous months later. This is a common error, which explains accidents in the middle of winter, far from the original plot.

Why were my sheep affected this year and not previous years on the same plot?

Because the content of the plant depends on the conditions of the year: drought followed by rain, recent fertilization, frost or hail cause nitrates to rise in a crop that was safe the year before. It is the context that creates the risk, not just the plant.

Is there anything I can do while waiting for the vet?

Remove the fodder or take the lot out of the plot, calmly, without making anyone run, and put the animals in the shade in a quiet area with clean water. Do not administer anything by mouth. An animal that lacks oxygen and is made to run dies on the spot.

Are the animals that are doing well out of the woods?

Not necessarily. Not everyone has eaten the same amount and the signs do not appear at the same time. The entire flock should be monitored for several hours and reported to the veterinarian, even for those that appear normal.