Nitrate Poisoning in Cattle

Nitrate poisoning can strike cattle that eat forage that looked perfectly healthy. Knowing when plants accumulate nitrate and testing feed before you use it are the best protections.

Key points

Stressed plants can hold high nitrate even when they look normal.
Drought, frost, hail and heavy fertilization are common triggers.
Only a lab test can tell you whether forage is risky.
Never experiment with feeding plans on suspect forage; consult a nutritionist.
Call the vet right away if cattle show breathing trouble or die suddenly.

What nitrate poisoning is

Plants take up nitrogen from soil in the form of nitrate and normally convert it into protein. Under stress, some plants take up nitrate faster than they can process it, and it builds up in the stalks and lower leaves. When cattle eat that forage, rumen microbes convert nitrate into nitrite, and nitrite interferes with the blood's ability to carry oxygen.

The animal effectively suffocates from the inside, even though it is breathing. That is why signs can appear quickly and why death losses can be sudden.

The condition is easy to confuse with other causes of sudden death, so a clear history helps your vet. Write down what changed in the last day or two: new field, new hay, weather, fertilizer or herbicide use.

Conditions that raise the risk

Drought is the best-known trigger, but it is not the only one. Plant stress from hail, frost, cloudy weather, herbicide use, or heavy nitrogen fertilization or manure applications can all lead to nitrate build-up. Rain after a drought can cause a rapid uptake, and the risk can linger after the rain.

Common problem forages include sorghum types, sudangrass, corn, small grains, certain weeds and some brassicas. Do not assume a forage is safe just because it was fine last year.

What cattle look like when affected

Signs are linked to low oxygen in the blood. Cattle may show rapid breathing, weakness, staggering or trembling, and in serious cases collapse and death. Mucous membranes may look brownish or muddy instead of a healthy pink.

Hungry cattle that eat a lot quickly are at higher risk, and a sudden death in a group that was recently moved to new forage should raise suspicion.

Fast, labored breathing
Weakness, stumbling or trembling
Brownish or muddy-looking gums
Sudden death shortly after eating
Late-term cows aborting after exposure

Testing is the key step

Because nitrate cannot be seen or smelled, forage testing is the only reliable way to know. Work with your extension office or a forage lab, and ask for guidance on how to sample, because the stalk base often holds more than the leaves. Ask the lab or extension specialist how to interpret the report and what the safe feeding approach is for your cattle.

No single number fits every case, because interpreting a result depends on the animal, the ration and the rest of the feed. Ask a nutritionist or extension specialist for the guidance that fits your herd.

Managing risky forage

If a test shows nitrate is a problem, you still may have options. A nutritionist may suggest ways to manage the feed, such as blending with other feeds or changing how and when it is fed. Do not try these on your own.

Cattle need time to adapt to forages that carry some nitrate, and hungry cattle should not be given unlimited access to suspect feed. Harvest timing and cutting height can also change how much nitrate ends up in hay or silage.

Water can carry nitrate too, particularly from shallow wells or ponds near feedlots and heavily fertilized fields. Ask your extension office about water testing if your supply could be affected, and keep in mind that feed and water add together.

If you suspect poisoning

Remove cattle from the suspect feed or pasture calmly and call your veterinarian immediately. Treatment is time sensitive and has to be directed by a vet. Handle animals gently, because stress and exertion make things worse.

Keep a sample of the suspect forage for the lab, and record what the cattle ate and when. Withdrawal times on any treatment must be followed exactly.

Do not feed the suspect forage to other groups while you wait for answers, and do not bury or move a carcass before your vet advises. A diagnostic sample can help rule out other causes.

Common mistakes

Feeding drought-stressed forage untested is the main one. Others include turning hungry cattle onto a stressed field, ignoring weeds, assuming the water is the only risk, and forgetting that nitrate in stored hay does not go away. Test, plan and ask before you feed.

When to get help: Contact your extension office or a forage lab about testing, and ask a nutritionist how to feed any forage that tests high. Call your veterinarian immediately for cattle with breathing trouble, weakness or sudden death.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

More in Herd Health & Cattle Care

← Bloat in Cattle: Causes and Response Prussic Acid Poisoning in Forages →