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Nitrate Awareness: Is Your Herd Safe?

By   /  November 28, 2016  /  No Comments

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I just got the forage test results back from the lab and the nitrate score was 3,000. Am I in trouble?

Every year I get multiple questions similar to this one. Unfortunately, with just this information I’m unable to give a useful answer. So – the first question I ask is “Was this reported as nitrates or as nitrate nitrogen?”

Thanks to the Colorado State University Veterinary Diagnostic Laboratories for this list.

Thanks to the Colorado State University Veterinary Diagnostic Laboratories for this list.

Why is it important to know the difference between nitrate nitrogen and nitrates? Well, using the example above, if the score was 3,000 parts per million of nitrate nitrogen, then the forage may have a nitrate concentration that is almost 50 percent higher than what we often consider to be the potentially toxic level for nitrate nitrogen. It would be risky for cattle to eat this forage without taking some precautions.

However, if the score was 3,000 parts per million of nitrate there should be no worries since this is less than one-third the danger level for nitrates. So the same score or value can range from quite dangerous to perfectly safe depending on how it is reported.

So what is the reason for these big differences? Basically, it comes down to how each individual laboratory tests for and then reports results for nitrates. When a laboratory reports directly the concentration of nitrate, it is referring specifically to the nitrate ion, which is designated chemically as NO3-. Most labs and advisors consider a level of 9,000 to 10,000 parts per million of the nitrate ion to be the level where toxicity concerns begin.

Some labs, though, report the amount of nitrogen that is in the nitrate ion and call it nitrate nitrogen and report it chemically as NO3-N. Nitrate is one part nitrogen plus three parts oxygen so nitrogen only makes up about 22.6 percent on the nitrate ion. Thus, a much smaller amount of nitrate nitrogen is needed to produce the same effect as the entire nitrate ion. As a result, the danger level for nitrate nitrogen begins somewhere between 2,000 and 2,300.

Is one method better than the other? No – both give the same result and either one can be used to determine the safety of your feed. In fact, it is easy to mathematically convert between nitrate and nitrate nitrogen by using the following formulas:

Nitrate = Nitrate Nitrogen x 4.43
Nitrate Nitrogen = Nitrate x 0.226

Next time you test your hay or corn stalks or cover crop for nitrates, look closely at the report to see what method your lab used to report your nitrate results. Then, if you want to talk with someone about the safety or feeding alternatives for your forage you can be sure both of you are talking the same language.

Grazing Risk

Risk associated with grazing high nitrate forages is a bit less than when feeding them. One reason is that the animals tend to be consume the feed more slowly than when they’re being fed hay or silage. That gives the digestive system more time to process the nitrates into ammonia. Also, when they graze they can select parts of the plant that are lower in nitrates than the whole plant analysis would indicate. That way the diet itself is at a safer level. Last, green feeds, like you get when you’re grazing cover crops, tend to release the nitrates more slowly out of the tissue, again giving the animal more time to neutralize the nitrates.

Reducing the Risk

If you’re dealing with high nitrate feeds, take a look at ways you can dilute the total diet of nitrates. In a feeding situation you can add a palatable feed stuff to the mix that would dilute the amount of total nitrates in the diet and make the diet as a whole safe. In a grazing situation you might add a supplement, or very palatable hay to dilute the overall diet.

You can also help your animals adapt to the higher nitrate diet. It takes rumen microbes about a week to adjust to higher nitrate feeds. You can adapt your animals by giving them a few hours access to the nitrate feed on day one, and increasing the time over the week.

Keep in mind that pregnant animals are less tolerant of nitrates than stockers. The fetus may end up being shorted of oxygen in the blood stream and that can lead to fetal stress and abortion. Consider feeding lower-nitrate feeds to your pregnant stock, especially if they will be eating it all winter long.

Some folks ask, “Can I feed one bale of high and one of low nitrate feeds? Or do I have to grind and mix them?” It’s safer to grind and blend the feeds even if you have both bales out at the same time. The problem is that we don’t know which animals will eat how much of which bale. If you want your animals to adapt to the higher nitrates, feeding a high nitrate feed one day and another feed the next doesn’t help them adapt.

Symptoms to Watch For

A comparison of blood color from an animal with nitrate poisoning and a healthy animal.

A comparison of blood color from an animal with nitrate poisoning and a healthy animal.

If you’re feeding a high nitrate feed be alert to the symptoms of stress. Signs of nitrate poisoning are related to a lack of oxygen in the blood. The onsets of symptoms are very rapid and include:

• Bluish/chocolate brown gums
• Rapid, difficult and noisy breathing
• Rapid pulse
• Salivation, bloat, tremors, staggering
• Dark “chocolate-coloured” blood

Treatment is via intravenous dosing of a solution of methylene blue, which restores the iron in the haemoglobin to its ferrous state allowing it to carry oxygen again.

The BeefWatch podcasts from University of Nebraska-Lincoln provide a lot of great information. Check them out! 

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About the author

Bruce is a professor of agronomy and extension forage specialist at the University of Nebraska-Lincoln. He works with grazing systems and does research on annual forages, utilization of warm-season grasses, forage quality in hay and pasture systems and using legumes to improve pastures.

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